Tag Archives: E. coli

Resisting silver’s microbial properties?

Yes, it is possible for bacteria to become resistant to silver nanoparticles. However, that yes comes with some qualifications according to a July 13, 2021 news item on ScienceDaily (Note: Links have been removed),

Antimicrobials are used to kill or slow the growth of bacteria, viruses and other microorganisms. They can be in the form of antibiotics, used to treat bodily infections, or as an additive or coating on commercial products used to keep germs at bay. These life-saving tools are essential to preventing and treating infections in humans, animals and plants, but they also pose a global threat to public health when microorganisms develop resistance to them, a concept known as antimicrobial resistance.

One of the main drivers of antimicrobial resistance is the misuse and overuse of antimicrobial agents, which includes silver nanoparticles, [emphases mine] an advanced material with well-documented antimicrobial properties. It is increasingly used in commercial products that boast enhanced germ-killing performance — it has been woven into textiles, coated onto toothbrushes, and even mixed into cosmetics as a preservative.

The Gilbertson Group at the University of Pittsburgh [Pennsylvania, US} Swanson School of Engineering used laboratory strains of E.coli to better understand bacterial resistance to silver nanoparticles and attempt to get ahead of the potential misuse of this material. The team recently published their results in Nature Nanotechnology.

Caption: A depiction of hyper-motile E.coli, a strain of bacteria found to resist silver nanoparticles’ antimicrobial properties after repeated exposure. Credit: Lisa Stabryla/University of Pittsburgh.

A July 13, 2021 University of Pittsburgh news release (also on EurekAlert), which originated the news item, provides more insight into the research,

“Bacterial resistance to silver nanoparticles is understudied, so our group looked at the mechanisms behind this event,” said Lisa Stabryla, lead author on the paper and a recent civil and environmental PhD graduate at Pitt. “This is a promising innovation to add to our arsenal of antimicrobials, but we need to consciously study it and perhaps regulate its use to avoid decreased efficacy like we’ve seen with some common antibiotics.”

Stabryla exposed E.coli to 20 consecutive days of silver nanoparticles and monitored bacterial growth over time. Nanoparticles are roughly 50 times smaller than a bacterium.

“In the beginning, bacteria could only survive at low concentrations of silver nanoparticles, but as the experiment continued, we found that they could survive at higher doses,” Stabryla noted. “Interestingly, we found that bacteria developed resistance to the silver nanoparticles but not their released silver ions alone.”

The group sequenced the genome of the E.coli that had been exposed to silver nanoparticles and found a mutation in a gene that corresponds to an efflux pump that pushes heavy metal ions out of the cell.

“It is possible that some form of silver is getting into the cell, and when it arrives, the cell mutates to quickly pump it out,” she added. “More work is needed to determine if researchers can perhaps overcome this mechanism of resistance through particle design.”

The group then studied two different types of E.coli: a hyper-motile strain that swims through its environment more quickly than normally motile bacteria and a non-motile strain that does not have physical means for moving around. They found that only the hyper-motile strain developed resistance.

“This finding could suggest that silver nanoparticles may be a good option to target certain types of bacteria, particularly non-motile strains,” Stabryla said.

In the end, bacteria will still find a way to evolve and evade antimicrobials. The hope is that an understanding of the mechanisms that lead to this evolution and a mindful use of new antimicrobials will lessen the impact of antimicrobial resistance.

“We are the first to look at bacterial motility effects on the ability to develop resistance to silver nanoparticles,” said Leanne Gilbertson, assistant professor of civil and environmental engineering at Pitt. “The observed difference is really interesting and merits further investigation to understand it and how to link the genetic response – the efflux pump regulation – to the bacteria’s ability to move in the system.

“The results are promising for being able to tune particle properties for a desired response, such as high efficacy while avoiding resistance.”

Here’s a link to and a citation for the paper,

Role of bacterial motility in differential resistance mechanisms of silver nanoparticles and silver ions by Lisa M. Stabryla, Kathryn A. Johnston, Nathan A. Diemler, Vaughn S. Cooper, Jill E. Millstone, Sarah-Jane Haig & Leanne M. Gilbertson. Nature Nanotechnology (2021) DOI: https://doi.org/10.1038/s41565-021-00929-w Published: 21 June 2021

This paper appears to be open access.

Food sensor made from of silk microneedles looks like velco

These sensors really do look like velcro,

The Velcro-like food sensor, made from an array of silk microneedles, can pierce through plastic packaging to sample food for signs of spoilage and bacterial contamination. Image: Felice Frankel

A September 9, 2020 news item on Nanowerk announces some research from the Massachusetts Institute (MIT),

MIT engineers have designed a Velcro-like food sensor, made from an array of silk microneedles, that pierces through plastic packaging to sample food for signs of spoilage and bacterial contamination.

The sensor’s microneedles are molded from a solution of edible proteins found in silk cocoons, and are designed to draw fluid into the back of the sensor, which is printed with two types of specialized ink. One of these “bioinks” changes color when in contact with fluid of a certain pH range, indicating that the food has spoiled; the other turns color when it senses contaminating bacteria such as pathogenic E. coli.

A Sept. 9, 2020 MIT news release (also on EurekAlert), which originated the news item, delves further into the research,

The researchers attached the sensor to a fillet of raw fish that they had injected with a solution contaminated with E. coli. After less than a day, they found that the part of the sensor that was printed with bacteria-sensing bioink turned from blue to red — a clear sign that the fish was contaminated. After a few more hours, the pH-sensitive bioink also changed color, signaling that the fish had also spoiled.

The results, published today in the journal Advanced Functional Materials, are a first step toward developing a new colorimetric sensor that can detect signs of food spoilage and contamination.

Such smart food sensors might help head off outbreaks such as the recent salmonella contamination in onions and peaches. They could also prevent consumers from throwing out food that may be past a printed expiration date, but is in fact still consumable.

“There is a lot of food that’s wasted due to lack of proper labeling, and we’re throwing food away without even knowing if it’s spoiled or not,” says Benedetto Marelli, the Paul M. Cook Career Development Assistant Professor in MIT’s Department of Civil and Environmental Engineering. “People also waste a lot of food after outbreaks, because they’re not sure if the food is actually contaminated or not. A technology like this would give confidence to the end user to not waste food.”

Marelli’s co-authors on the paper are Doyoon Kim, Yunteng Cao, Dhanushkodi Mariappan, Michael S. Bono Jr., and A. John Hart.

Silk and printing

The new food sensor is the product of a collaboration between Marelli, whose lab harnesses the properties of silk to develop new technologies, and Hart, whose group develops new manufacturing processes.

Hart recently developed a high-resolution floxography technique, realizing microscopic patterns that can enable low-cost printed electronics and sensors. Meanwhile, Marelli had developed a silk-based microneedle stamp that penetrates and delivers nutrients to plants. In conversation, the researchers wondered whether their technologies could be paired to produce a printed food sensor that monitors food safety.

“Assessing the health of food by just measuring its surface is often not good enough. At some point, Benedetto mentioned his group’s microneedle work with plants, and we realized that we could combine our expertise to make a more effective sensor,” Hart recalls.

The team looked to create a sensor that could pierce through the surface of many types of food. The design they came up with consisted of an array of microneedles made from silk.

“Silk is completely edible, nontoxic, and can be used as a food ingredient, and it’s mechanically robust enough to penetrate through a large spectrum of tissue types, like meat, peaches, and lettuce,” Marelli says.

A deeper detection

To make the new sensor, Kim first made a solution of silk fibroin, a protein extracted from moth cocoons, and poured the solution into a silicone microneedle mold. After drying, he peeled away the resulting array of microneedles, each measuring about 1.6 millimeters long and 600 microns wide — about one-third the diameter of a spaghetti strand.

The team then developed solutions for two kinds of bioink — color-changing printable polymers that can be mixed with other sensing ingredients. In this case, the researchers mixed into one bioink an antibody that is sensitive to a molecule in E. coli. When the antibody comes in contact with that molecule, it changes shape and physically pushes on the surrounding polymer, which in turn changes the way the bioink absorbs light. In this way, the bioink can change color when it senses contaminating bacteria.

The researchers made a bioink containing antibodies sensitive to E. coli, and a second bioink sensitive to pH levels that are associated with spoilage. They printed the bacteria-sensing bioink on the surface of the microneedle array, in the pattern of the letter “E,” next to which they printed the pH-sensitive bioink, as a “C.” Both letters initially appeared blue in color.

Kim then embedded pores within each microneedle to increase the array’s ability to draw up fluid via capillary action. To test the new sensor, he bought several fillets of raw fish from a local grocery store and injected each fillet with a fluid containing either E. coli, Salmonella, or the fluid without any contaminants. He stuck a sensor into each fillet. Then, he waited.

After about 16 hours, the team observed that the “E” turned from blue to red, only in the fillet contaminated with E. coli, indicating that the sensor accurately detected the bacterial antigens. After several more hours, both the “C” and “E” in all samples turned red, indicating that every fillet had spoiled.

The researchers also found their new sensor indicates contamination and spoilage faster than existing sensors that only detect pathogens on the surface of foods.

“There are many cavities and holes in food where pathogens are embedded, and surface sensors cannot detect these,” Kim says. “So we have to plug in a bit deeper to improve the reliability of the detection. Using this piercing technique, we also don’t have to open a package to inspect food quality.”

The team is looking for ways to speed up the microneedles’ absorption of fluid, as well as the bioinks’ sensing of contaminants. Once the design is optimized, they envision the sensor could be used at various stages along the supply chain, from operators in processing plants, who can use the sensors to monitor products before they are shipped out, to consumers who may choose to apply the sensors on certain foods to make sure they are safe to eat.

Here’s a link to and a citation for the paper,

A Microneedle Technology for Sampling and Sensing Bacteria in the Food Supply Chain by Doyoon Kim, Yunteng Cao, Dhanushkodi Mariappan, Michael S. Bono Jr., A. John Hart, Benedetto Marelli. DOI: https://doi.org/10.1002/adfm.202005370 First published: 09 September 2020

This paper is behind a paywall.

The decade that was (2010-19) and the decade to come (2020-29): Science culture in Canada (an addendum)

I missed a few science journalists (part 1 of this series, under the Science Communication subhead; Mainstream Media, sub subhead) as the folks at the Science Media Centre of Canada (SMCC) noted on Twitter,

Science Media Centre @SMCCanada Apr 16 Replying to @frogheart

Thanks for the mention. But I think poor @katecallen at the Toronto Star would be dismayed to read that @IvanSemeniuk is the only science reporter on a Canadian newspaper. And @row1960 Bob Weber at Canadian Press is carried in every newspaper in the country.

Science Media Centre @SMCCanada Apr 16 Replying to @frogheart

In addition, @mle_chung at CBC News Online (#1 news source in Canada) is read more than any other science writer in the country, as is her colleague @NebulousNikki

Thank you.

***ETA April 29, 2020 at 0910 PT: Yesterday, April 28, 2020, Postmedia announced that it was closing 15 community newspapers and a number of jobs elsewhere in the organization. Earlier in the month on April 7, 2020 Postmedia announced that 85 positions were being eliminated, including 11 in the editorial department of TorStar (Toronto Star). I hope they keep a position for a science writer at the Toronto Star.***

Alice Major, a poet mentioned in Part 3 under The word subhead; Poetry sub subhead, wrote with news of two other poets who focus on science in their work.

  • Christian Bök
  • Adam Dickinson

From Bök’s Wikipedia entry (Note: Links have been removed),

Christian Bök[needs IPA] (born August 10, 1966 in Toronto, Canada) is an experimental Canadian poet. He is the author of Eunoia, which won the Canadian Griffin Poetry Prize.

On April 4, 2011 Bök announced a significant break-through in his 9-year project to engineer “a life-form so that it becomes not only a durable archive for storing a poem, but also an operant machine for writing a poem”.[7][8] On the previous day (April 3) Bök said he received confirmation from the laboratory at the University of Calgary that my poetic cipher, gene X-P13, has in fact caused E. coli to fluoresce red in our test-runs—meaning that, when implanted in the genome of this bacterium, my poem (which begins “any style of life/ is prim…”) does in fact cause the bacterium to write, in response, its own poem (which begins “the faery is rosy/ of glow…”).”[9]

The project has continued for over fifteen years at a cost exceeding $110,000 and he hopes to finish the project in 2014.[10] He published “Book I” of the resulting Xenotext in 2015.

Xenotext: Book 1 published by Coach House Books is described this way,

Internationally best-sellling poet Christian Bök has spent more than ten years writing what promises to be the first example of ‘living poetry.’ After successfully demonstrating his concept in a colony of E. coli, Bök is on the verge of enciphering a beautiful, anomalous poem into the genome of an unkillable bacterium (Deinococcus radiodurans), which can, in turn, “read” his text, responding to it by manufacturing a viable, benign protein, whose sequence of amino acids enciphers yet another poem. The engineered organism might conceivably serve as a post-apocalyptic archive, capable of outlasting our civilization.

Book I of The Xenotext constitutes a kind of ‘demonic grimoire,’ providing a scientific framework for the project with a series of poems, texts, and illustrations. A Virgilian welcome to the Inferno, Book I is the “orphic” volume in a diptych, addressing the pastoral heritage of poets, who have sought to supplant nature in both beauty and terror. The book sets the conceptual groundwork for the second volume, which will document the experiment itself. The Xenotext is experimental poetry in the truest sense of the term.

Adam Dickinson is a poet and an associate professor at Brock University (Ontario). He describes himself and his work this way (from the Brock University bio page),

Adam Dickinson is a poet and a professor of poetry. His creative and academic writing has primarily focused on intersections between poetry and science as a way of exploring new ecocritical perspectives and alternative modes of poetic composition. His latest book, Anatomic (Coach House Books), involves the results of chemical and microbial testing on his body, and was shortlisted for The Raymond Souster Award. Sections of it were also shortlisted for the Canadian Broadcasting Corporation (CBC) Poetry Prize. His book, The Polymers (House of Anansi [2013]), which is an imaginary science project that combines the discourses, theories, and experimental methods of the science of plastic materials with the language and culture of plastic behaviour, was a finalist for both the Governor General’s Award for Poetry and the Trillium Book Award for Poetry. He has published two previous books, Kingdom, Phylum (also nominated for the Trillium Book Award for Poetry) and Cartography and Walking (nominated for an Alberta Book Award). His scholarly work (supported by SSHRC [Social Sciences and Humanities Research Council of Canada]) brings together research in innovative poetics, biosemiotics, pataphysics, and Anthropocene studies.

His current research-creation project, “Metabolic Poetics,” (also supported by SSHRC) is concerned with the potential of expanded modes of reading and writing to shift the frames and scales of conventional forms of signification in order to bring into focus the often inscrutable biological and cultural writing intrinsic to the Anthropocene, especially as this is reflected in the inextricable link between the metabolic processes of human and nonhuman bodies and the global metabolism of energy and capital.

He has been featured at prominent international literary festivals, such as Poetry International in Rotterdam, The Harbourfront International Festival of Authors in Toronto, and the Oslo International Poetry Festival in Norway. Adam has also been a finalist for the K.M. Hunter Artist Award in Literature, Administered by the Ontario Arts Council. Adam welcomes potential student supervisions on topics in poetry and poetics, environmental writing, science and literature, and creative writing.

Thank you.

This last addition may seen a little offbeat but ARPICO (Society of Italian Researchers & Professionals in Western Canada) has hosted a surprisingly large number of science events in Vancouver. Two recent examples include: The Eyes are the Windows to The Mind; Implications for Artificial Intelligence (AI) -driven Personalized Interaction on March 4, 2020 and, the relatively recent, Whispers in the Dark: Underground Science on June 12, 2019.

Hopefully, I’ll be able to resist the impulse to make any more additions.

***ETA April 30, 2020: Research2Reality (R2R) was launched in 2015 as a social media initiative featuring a series of short video interviews with Canadian scientists (see more in my May 11, 2015 posting). Almost five years later, the website continues to feature interviews and it also hosts news about Canadian science and research. R2R was founded by Molly Shoichet (pronounced shoyquette) and Mike MacMillan.***

For anyone who stumbled across this addendum first, it fits on to the end of a 5-part series:

Part 1 covers science communication, science media (mainstream and others such as blogging) and arts as exemplified by music and dance: The decade that was (2010-19) and the decade to come (2020-29): Science culture in Canada (1 of 5).

Part 2 covers art/science (or art/sci or sciart) efforts, science festivals both national and local, international art and technology conferences held in Canada, and various bar/pub/café events: The decade that was (2010-19) and the decade to come (2020-29): Science culture in Canada (2 of 5).

Part 3 covers comedy, do-it-yourself (DIY) biology, chief science advisor, science policy, mathematicians, and more: The decade that was (2010-19) and the decade to come (2020-29): Science culture in Canada (3 of 5).

Part 4 covers citizen science, birds, climate change, indigenous knowledge (science), and the IISD Experimental Lakes Area: The decade that was (2010-19) and the decade to come (2020-29): Science culture in Canada (4 of 5).

Part 5: includes science podcasting, eco art, a Saskatchewan lab with an artist-in-residence, the Order of Canada and children’s science literature, animation and mathematics, publishing science, *French language science media,* and more: The decade that was (2010-19) and the decade to come (2020-29): Science culture in Canada (5 of 5).

*French language science media added December 9, 2020.

Altered virus spins gold into beads

They’re not calling this synthetic biology but I’ m pretty sure that altering a virus gene so the virus can spin gold (Rumpelstiltskin anyone?) qualifies. From an August 24, 2018 news item on ScienceDaily,

The race is on to find manufacturing techniques capable of arranging molecular and nanoscale objects with precision.

Engineers at the University of California, Riverside, have altered a virus to arrange gold atoms into spheroids measuring a few nanometers in diameter. The finding could make production of some electronic components cheaper, easier, and faster.

An August 23, 2018 University of California at Riverside (UCR) news release (also on EurekAlett) by Holly Ober, which originated the news item, adds detail,

“Nature has been assembling complex, highly organized nanostructures for millennia with precision and specificity far superior to the most advanced technological approaches,” said Elaine Haberer, a professor of electrical and computer engineering in UCR’s Marlan and Rosemary Bourns College of Engineering and senior author of the paper describing the breakthrough. “By understanding and harnessing these capabilities, this extraordinary nanoscale precision can be used to tailor and build highly advanced materials with previously unattainable performance.”

Viruses exist in a multitude of shapes and contain a wide range of receptors that bind to molecules. Genetically modifying the receptors to bind to ions of metals used in electronics causes these ions to “stick” to the virus, creating an object of the same size and shape. This procedure has been used to produce nanostructures used in battery electrodes, supercapacitors, sensors, biomedical tools, photocatalytic materials, and photovoltaics.

The virus’ natural shape has limited the range of possible metal shapes. Most viruses can change volume under different scenarios, but resist the dramatic alterations to their basic architecture that would permit other forms.

The M13 bacteriophage, however, is more flexible. Bacteriophages are a type of virus that infects bacteria, in this case, gram-negative bacteria, such as Escherichia coli, which is ubiquitous in the digestive tracts of humans and animals. M13 bacteriophages genetically modified to bind with gold are usually used to form long, golden nanowires.

Studies of the infection process of the M13 bacteriophage have shown the virus can be converted to a spheroid upon interaction with water and chloroform. Yet, until now, the M13 spheroid has been completely unexplored as a nanomaterial template.

Haberer’s group added a gold ion solution to M13 spheroids, creating gold nanobeads that are spiky and hollow.

“The novelty of our work lies in the optimization and demonstration of a viral template, which overcomes the geometric constraints associated with most other viruses,” Haberer said. “We used a simple conversion process to make the M13 virus synthesize inorganic spherical nanoshells tens of nanometers in diameter, as well as nanowires nearly 1 micron in length.”

The researchers are using the gold nanobeads to remove pollutants from wastewater through enhanced photocatalytic behavior.

The work enhances the utility of the M13 bacteriophage as a scaffold for nanomaterial synthesis. The researchers believe the M13 bacteriophage template transformation scheme described in the paper can be extended to related bacteriophages.

Here’s a link to and a citation for the paper,

M13 bacteriophage spheroids as scaffolds for directed synthesis of spiky gold nanostructures by Tam-Triet Ngo-Duc, Joshua M. Plank, Gongde Chen, Reed E. S. Harrison, Dimitrios Morikis, Haizhou Liu, and Elaine D. Haberer. Nanoscale, 2018,10, 13055-13063 DOI: 10.1039/C8NR03229G First published on 25 Jun 2018

This paper is behind a paywall.

For another example of genetic engineering and synthetic biology, see my July 18, 2018 posting: Genetic engineering: an eggplant in Bangladesh and a synthetic biology grant at Concordia University (Canada).

For anyone unfamiliar with the Rumpelstiltskin fairytale about spinning straw into gold, see its Wikipedida entry.

An artificial enzyme uses light to kill bacteria

An April 4, 2018 news item on ScienceDaily announces a light-based approach to killing bacteria,

Researchers from RMIT University [Australia] have developed a new artificial enzyme that uses light to kill bacteria.

The artificial enzymes could one day be used in the fight against infections, and to keep high-risk public spaces like hospitals free of bacteria like E. coli and Golden Staph.

E. coli can cause dysentery and gastroenteritis, while Golden Staph is the major cause of hospital-acquired secondary infections and chronic wound infections.

Made from tiny nanorods — 1000 times smaller than the thickness of the human hair — the “NanoZymes” use visible light to create highly reactive oxygen species that rapidly break down and kill bacteria.

Lead researcher, Professor Vipul Bansal who is an Australian Future Fellow and Director of RMIT’s Sir Ian Potter NanoBioSensing Facility, said the new NanoZymes offer a major cutting edge over nature’s ability to kill bacteria.

Dead bacteria made beautiful,

Caption: A 3-D rendering of dead bacteria after it has come into contact with the NanoZymes.
Credit: Dr. Chaitali Dekiwadia/ RMIT Microscopy and Microanalysis Facility

An April 5, 2018 RMIT University press release (also on EurekAlert but dated April 4, 2018), which originated the news item, expands on the theme,

“For a number of years we have been attempting to develop artificial enzymes that can fight bacteria, while also offering opportunities to control bacterial infections using external ‘triggers’ and ‘stimuli’,” Bansal said. “Now we have finally cracked it.

“Our NanoZymes are artificial enzymes that combine light with moisture to cause a biochemical reaction that produces OH radicals and breaks down bacteria. Nature’s antibacterial activity does not respond to external triggers such as light.

“We have shown that when shined upon with a flash of white light, the activity of our NanoZymes increases by over 20 times, forming holes in bacterial cells and killing them efficiently.

“This next generation of nanomaterials are likely to offer new opportunities in bacteria free surfaces and controlling spread of infections in public hospitals.”

The NanoZymes work in a solution that mimics the fluid in a wound. This solution could be sprayed onto surfaces.

The NanoZymes are also produced as powders to mix with paints, ceramics and other consumer products. This could mean bacteria-free walls and surfaces in hospitals.

Public toilets — places with high levels of bacteria, and in particular E. coli — are also a prime location for the NanoZymes, and the researchers believe their new technology may even have the potential to create self-cleaning toilet bowls.

While the NanoZymes currently use visible light from torches or similar light sources, in the future they could be activated by sunlight.

The researchers have shown that the NanoZymes work in a lab environment. The team is now evaluating the long-term performance of the NanoZymes in consumer products.

“The next step will be to validate the bacteria killing and wound healing ability of these NanoZymes outside of the lab,” Bansal said.

“This NanoZyme technology has huge potential, and we are seeking interest from appropriate industries for joint product development.”

Here’s a link to and a citation for the paper,

Visible-Light-Triggered Reactive-Oxygen-Species-Mediated Antibacterial Activity of Peroxidase-Mimic CuO Nanorods by Md. Nurul Karim, Mandeep Singh, Pabudi Weerathunge, Pengju Bian, Rongkun Zheng, Chaitali Dekiwadia, Taimur Ahmed, Sumeet Walia, Enrico Della Gaspera, Sanjay Singh, Rajesh Ramanathan, and Vipul Bansal. ACS Appl. Nano Mater., Article ASAP DOI: 10.1021/acsanm.8b00153 Publication Date (Web): March 6, 2018

Copyright © 2018 American Chemical Society

This paper is open access.

Australian peacock spiders, photonic nanostructures, and making money

Researcher Bor-Kai Hsiung’s work has graced this blog before but the topic was tarantulas and their structural colour. This time, it’s all about Australian peacock spiders and their structural colour according to a December 22, 2017 news item on ScienceDaily,

Even if you are arachnophobic, you probably have seen pictures or videos of Australian peacock spiders (Maratus spp.). These tiny spiders are only 1-5 mm long but are famous for their flamboyant courtship displays featuring diverse and intricate body colorations, patterns, and movements.

The spiders extremely large anterior median eyes have excellent color vision and combine with their bright colors to make peacock spiders cute enough to cure most people of their arachnophobia. But these displays aren’t just pretty to look at, they also inspire new ways for humans to produce color in technology.

One species of peacock spider — the rainbow peacock spider (Maratus robinsoni) is particularly neat, because it showcases an intense rainbow iridescent signal in males’ courtship displays to the females. This is the first known instance in nature of males using an entire rainbow of colors to entice females. Dr. Bor-Kai Hsiung led an international team of researchers from the US (UAkron, Cal Tech, UC San Diego, UNL [University of Nebraska-Lincoln]), Belgium (Ghent University), Netherlands (UGroningen), and Australia to discover how rainbow peacock spiders produce this unique multi-color iridescent signal.

A December 22, 2017 Ghent University (Belgium) press release on Alpha Galileo, which originated the news item, provides more technical detail,

Using a diverse array of research techniques, including light and electron microscopy, hyperspectral imaging, imaging scatterometry, nano 3D printing and optical modeling, the team found the origin of this intense rainbow iridescence emerged from specialized abdominal scales of the spiders. These scales have an airfoil-like microscopic 3D contour with nanoscale diffraction grating structures on the surface.

The interaction between the surface nano-diffraction grating and the microscopic curvature of the scales enables separation and isolation of light into its component wavelengths at finer angles and smaller distances than are possible with current manmade engineering technologies.

Inspiration from these super iridescent scales can be used to overcome current limitations in spectral manipulation, and to further reduce the size of optical spectrometers for applications where fine-scale spectral resolution is required in a very small package, notably instruments on space missions, or wearable chemical detection systems. And it could have a wide array of implications to fields ranging from life sciences and biotechnologies to material sciences and engineering.

Here’s a video of an Australian rainbow peacock spider,

Here’s more from the YouTube description published on April 13, 2017 by Peacockspiderman,

Scenes of Maratus robinsoni, a spider Peter Robinson discovered and David Hill and I named it after him in 2012. You can read our description on pages 36-41 in Peckhamia 103.2, which can be downloaded from the Peckhamia website http://peckhamia.com/peckhamia_number…. This is one of the two smallest species of peacock spider (2.5 mm long) and the only spider we know of in which colour changes occur every time it moves, this video was created to document this. Music: ‘Be Still’ by Johannes Bornlöf licensed through my MCN ‘Brave Bison’ from ‘Epidemic Sound’ For licensing inquiries please contact Brave Bison licensing@bravebison.io

The University of California at San Diego also published a December 22, 2017 news release about this work, which covers some of the same ground while providing a few new tidbits of information,

Brightly colored Australian peacock spiders (Maratus spp.) captivate even the most arachnophobic viewers with their flamboyant courtship displays featuring diverse and intricate body colorations, patterns, and movements – all packed into miniature bodies measuring less than five millimeters in size for many species. However, these displays are not just pretty to look at. They also inspire new ways for humans to produce color in technology.

One species of peacock spider – the rainbow peacock spider (Maratus robinsoni) – is particularly impressive, because it showcases an intense rainbow iridescent signal in males’ courtship displays to females. This is the first known instance in nature of males using an entire rainbow of colors to entice females to mate. But how do males make their rainbows? A new study published in Nature Communications looked to answer that question.

Figuring out the answers was inherently interdisciplinary so Bor-Kai Hsiung, a postdoctoral scholar at Scripps Institution of Oceanography at the University of California San Diego, assembled an international team that included biologists, physicists and engineers. Starting while he was a Ph.D. student at The University of Akron under the mentorship of Todd Blackledge and Matthew Shawkey, the team included researchers from UA, Scripps Oceanography, California Institute of Technology, and University of Nebraska-Lincoln, the University of Ghent in Belgium, University of Groningen in Netherlands, and Australia to discover how rainbow peacock spiders produce this unique iridescent signal.

The team investigated the spider’s photonic structures using techniques that included light and electron microscopy, hyperspectral imaging, imaging scatterometry and optical modeling to generate hypotheses about how the spider’s scale generate such intense rainbows. The team then used cutting-edge nano 3D printing to fabricate different prototypes to test and validate their hypotheses. In the end, they found that the intense rainbow iridescence emerged from specialized abdominal scales on the spiders. These scales combine an airfoil-like microscopic 3D contour with nanoscale diffraction grating structures on the surface. It is the interaction between the surface nano-diffraction grating and the microscopic curvature of the scales that enables separation and isolation of light into its component wavelengths at finer angles and smaller distances than are possible with current engineering technologies.

“Who knew that such a small critter would create such an intense iridescence using extremely sophisticated mechanisms that will inspire optical engineers,” said Dimitri Deheyn, Hsuing’s advisor at Scripps Oceanography and a coauthor of the study.

For Hsiung, the finding wasn’t quite so unexpected.

“One of the main questions that I wanted to address in my Ph.D. dissertation was ‘how does nature modulate iridescence?’ From a biomimicry perspective, to fully understand and address a question, one has to take extremes from both ends into consideration. I purposefully chose to study these tiny spiders with intense iridescence after having investigated the non-iridescent blue tarantulas,” said Hsiung.

The mechanism behind these tiny rainbows may inspire new color technology, but would not have been discovered without research combining basic natural history with physics and engineering, the researchers said.

“Nanoscale 3D printing allowed us to experimentally validate our models, which was really exciting,” said Shawkey. “We hope that these techniques will become common in the future.”

“As an engineer, what I found fascinating about these spider structural colors is how these long evolved complex structures can still outperform human engineering,” said Radwanul Hasan Siddique, a postdoctoral scholar at Caltech and study coauthor. “Even with high-end fabrication techniques, we could not replicate the exact structures. I wonder how the spiders assemble these fancy structural patterns in the first place!”

Inspiration from these super iridescent spider scales can be used to overcome current limitations in spectral manipulation, and to reduce the size of optical spectrometers for applications where fine-scale spectral resolution is required in a very small package, notably instruments on space missions, or wearable chemical detection systems.

In the end, peacock spiders don’t just produce nature’s smallest rainbows.They could also have implications for a wide array of fields ranging from life sciences and biotechnologies to material sciences and engineering.

Before citing the paper and providing a link, here’s a story by Robert F. Service for Science magazine about attempts to capitalize on ‘spider technology’, in this case spider silk,

The hype over spider silk has been building since 1710. That was the year François Xavier Bon de Saint Hilaire, president of the Royal Society of Sciences in Montpellier, France, wrote to his colleagues, “You will be surpriz’d to hear, that Spiders make a Silk, as beautiful, strong and glossy, as common Silk.” Modern pitches boast that spider silk is five times stronger than steel yet more flexible than rubber. If it could be made into ropes, a macroscale web would be able to snare a jetliner.

The key word is “if.” Researchers first cloned a spider silk gene in 1990, in hopes of incorporating it into other organisms to produce the silk. (Spiders can’t be farmed like silkworms because they are territorial and cannibalistic.) Today, Escherichia coli bacteria, yeasts, plants, silkworms, and even goats have been genetically engineered to churn out spider silk proteins, though the proteins are often shorter and simpler than the spiders’ own. Companies have managed to spin those proteins into enough high-strength thread to produce a few prototype garments, including a running shoe by Adidas and a lightweight parka by The North Face. But so far, companies have struggled to mass produce these supersilks.

Some executives say that may finally be about to change. One Emeryville, California-based startup, Bolt Threads, says it has perfected growing spider silk proteins in yeast and is poised to turn out tons of spider silk thread per year. In Lansing, Michigan, Kraig Biocraft Laboratories says it needs only to finalize negotiations with silkworm farms in Vietnam to produce mass quantities of a combination spider/silkworm silk, which the U.S. Army is now testing for ballistics protection. …

I encourage you to read Service’s article in its entirety if the commercialization prospects for spider silk interest you as it includes gems such as this,

Spider silk proteins are already making their retail debut—but in cosmetics and medical devices, not high-strength fibers. AMSilk grows spider silk proteins in E. coli and dries the purified protein into powders or mixes it into gels, for use as additives for personal care products, such as moisture-retaining skin lotions. The silk proteins supposedly help the lotions form a very smooth, but breathable, layer over the skin. Römer says the company now sells tons of its purified silk protein ingredients every year.

Finally, here’s a citation for and a link to the paper about Australian peacock spiders and nanophotonics,

Rainbow peacock spiders inspire miniature super-iridescent optics by Bor-Kai Hsiung, Radwanul Hasan Siddique, Doekele G. Stavenga, Jürgen C. Otto, Michael C. Allen, Ying Liu, Yong-Feng Lu, Dimitri D. Deheyn, Matthew D. Shawkey, & Todd A. Blackledge. Nature Communications 8, Article number: 2278 (2017) doi:10.1038/s41467-017-02451-x Published online: 22 December 2017

This paper is open access.

As for Bor-Kai Hsiung’s other mentions here:

How tarantulas get blue (December 7, 2015 posting)

Noniridescent photonics inspired by tarantulas (October 19, 2016 posting)

More on the blue tarantula noniridescent photonics (December 28, 2016 posting)

Bacteria and an anti-superbug coating from Ireland’s Sligo Institute of Technology

Unlike today’s (April 28, 2016) earlier piece about dealing with bacteria, the focus for this research is on superbugs and not the bacteria which form biofilm on medical implants and such. An April 21, 2016 news item on RTE News makes the announcement about a new means of dealing with superbugs,

A discovery by a team of scientists in Ireland could stem the spread of deadly superbugs predicted to kill millions of people worldwide over the coming decades.

The research has found an agent that can be baked into everyday items like smart-phones and door handles to combat the likes of MRSA and E. coli.

The nanotechnology has a 99.9 % kill rate of potentially lethal and drug-resistant bacteria, they say.

Lead scientist Professor Suresh C. Pillai, of Sligo Institute of Technology’s Nanotechnology Research Group, says the discovery is the culmination of 12 years work.

“This is a game changer,” he said.

“This breakthrough will change the whole fight against superbugs. It can effectively control the spread of bacteria.”

An April 21, 2016 Sligo Institute of Technology press release provides some context for the work and a few details about the coating,

News of the discovery comes just days after UK Chancellor of the Exchequer George Osborne warned that superbugs could become deadlier than cancer and are on course to kill 10 million people globally by 2050.

Speaking at the International Monetary Fund (IMF) in Washington, Mr Osborne warned that the problem would slash global GDP by around €100 trillion if it was not tackled.

Using nanotechnology, the discovery is an effective and practical antimicrobial solution — an agent that kills microorganisms or inhibits their growth — that can be used to protect a range of everyday items.

Items include anything made from glass, metallics and ceramics including computer or tablet screens, smartphones, ATMs, door handles, TVs, handrails, lifts, urinals, toilet seats, fridges, microwaves and ceramic floor or wall tiles.

It will be of particular use in hospitals and medical facilities which are losing the battle against the spread of killer superbugs.

Other common uses would include in swimming pools and public buildings, on glass in public buses and trains, sneeze guards protecting food in delis and restaurants as well as in clean rooms in the medical sector.

“It’s absolutely wonderful to finally be at this stage. This breakthrough will change the whole fight against superbugs. It can effectvely control the spread of bacteria,” said Prof. Pillai.

He continued: “Every single person has a sea of bacteria on their hands. The mobile phone is the most contaminated personal item that we can have. Bacteria grows on the phone and can live there for up to five months. As it is contaminated with proteins from saliva and from the hand, It’s fertile land for bacteria and has been shown to carry 30 times more bacteria than a toilet seat.”

The research started at Dublin Institute of Technology (DIT)’s CREST and involves scientists now based at IT Sligo, Dublin City University (DCU) and the University of Surrey. Major researchers included Dr Joanna Carroll and Dr Nigel S. Leyland.

It has been funded for the past eight years by John Browne, founder and CEO of Kastus Technologies Ltd, who is bringing the product to a global market. He was also supported by significant investment from Enterprise Ireland.

As there is nothing that will effectively kill antibiotic-resistant superbugs completely from the surface of items, scientists have been searching for a way to prevent the spread.

This has been in the form of building or ‘baking’ antimicrobial surfaces into products during the manufacturing process.

However, until now, all these materials were toxic or needed UV light in order to make them work. This meant they were not practical for indoor use and had limited commercial application.

“The challenge was the preparation of a solution that was activated by indoor light rather than UV light and we have now done that,” said Prof Pillai.

The new water-based solution can be sprayed onto any glass, ceramic or metallic surface during the production process, rendering the surface 99.9 per cent resistant to superbugs like MRSA, E. coli and other fungi. [emphasis mine]

The solution is sprayed on the product — such as a smartphone glass surface — and then ‘baked’ into it, forming a super-hard surface. The coating is transparent, permanent and scratch resistant and actually forms a harder surface than the original glass or ceramic material.

The team first developed the revolutionary material to work on ceramics and has spent the last five years adapting the formula – which is non-toxic and has no harmful bi-products ‑- to make it work on glass and metallic surfaces.

Research is now underway by the group on how to adapt the solution for use in plastics and paint, allowing even wider use of the protective material.

Prof Pillai, Kastus and the team have obtained a US and a UK patent on the unique process with a number of global patent applications pending. It is rare for such an academic scientific discovery to have such commercial viability.

“I was sold on this from the first moment I heard about it. It’s been a long road to here but it was such a compelling story that it was hard to walk away from so I had to see it through to the end,” said John Browne, Kastus CEO.

He continued: “This is a game changer. The uniqueness of antimicrobia surface treatment means that the applications for it in the real world are endless. The multinational glass manufacturers we are in negotiations with to sell the product to have been searching for years to come up with such a solution but have failed.”

If the coating kills 99.9%, doesn’t that mean 0.1% are immune? If that’s the case, won’t they reproduce and eventually establish themselves as a new kind of superbug?

Here’s a link to and a citation for the paper,

Highly Efficient F, Cu doped TiO2 anti-bacterial visible light active photocatalytic coatings to combat hospital-acquired infections by Nigel S. Leyland, Joanna Podporska-Carroll, John Browne, Steven J. Hinder, Brid Quilty, & Suresh C. Pillai. Scientific Reports 6, Article number: 24770 (2016) doi:10.1038/srep24770 Published online: 21 April 2016

This paper is open access.

Greening silver nanoparticles with lignin

A July 13, 2015 news item on phys.org highlights a new approach to making silver nanoparticles safer in the environment,

North Carolina State University researchers have developed an effective and environmentally benign method to combat bacteria by engineering nanoscale particles that add the antimicrobial potency of silver to a core of lignin, a ubiquitous substance found in all plant cells. The findings introduce ideas for better, greener and safer nanotechnology and could lead to enhanced efficiency of antimicrobial products used in agriculture and personal care.

A July 13, 2015 North Carolina State University (NCSU) news release (also on EurekAlert), which originated the news item, adds a bit more information,

As the nanoparticles wipe out the targeted bacteria, they become depleted of silver. The remaining particles degrade easily after disposal because of their biocompatible lignin core, limiting the risk to the environment.

“People have been interested in using silver nanoparticles for antimicrobial purposes, but there are lingering concerns about their environmental impact due to the long-term effects of the used metal nanoparticles released in the environment,” said Velev, INVISTA Professor of Chemical and Biomolecular Engineering at NC State and the paper’s corresponding author. “We show here an inexpensive and environmentally responsible method to make effective antimicrobials with biomaterial cores.”

The researchers used the nanoparticles to attack E. coli, a bacterium that causes food poisoning; Pseudomonas aeruginosa, a common disease-causing bacterium; Ralstonia, a genus of bacteria containing numerous soil-borne pathogen species; and Staphylococcus epidermis, a bacterium that can cause harmful biofilms on plastics – like catheters – in the human body. The nanoparticles were effective against all the bacteria.

The method allows researchers the flexibility to change the nanoparticle recipe in order to target specific microbes. Alexander Richter, the paper’s first author and an NC State Ph.D. candidate who won a 2015 Lemelson-MIT prize, says that the particles could be the basis for reduced risk pesticide products with reduced cost and minimized environmental impact.

“We expect this method to have a broad impact,” Richter said. “We may include less of the antimicrobial ingredient without losing effectiveness while at the same time using an inexpensive technique that has a lower environmental burden. We are now working to scale up the process to synthesize the particles under continuous flow conditions.”

I don’t quite understand how the silver nanoparticles/ions are rendered greener. I gather the lignin is harmless but where do the silver nanoparticles/ions go after they’ve been stripped of their lignin cover and have killed the bacteria? I did try reading the paper’s abstract (not much use for someone with my science level),

Silver nanoparticles have antibacterial properties, but their use has been a cause for concern because they persist in the environment. Here, we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and, together with silver ions, can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies have shown that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles.

If you can explain what happens to the silver nanoparticles, please let me know.

Meanwhile, here’s a link to and a citation for the paper,

An environmentally benign antimicrobial nanoparticle based on a silver-infused lignin core by Alexander P. Richter, Joseph S. Brown, Bhuvnesh Bharti, Amy Wang, Sumit Gangwal, Keith Houck, Elaine A. Cohen Hubal, Vesselin N. Paunov, Simeon D. Stoyanov, & Orlin D. Velev. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.141 Published online 13 July 2015

This paper is behind a paywall.

Customizing bacteria (E. coli) into squares, circles, triangles, etc.

The academic paper for this latest research from Delft University of Technology (TU Delft, Netherlands), uses the term ‘bacterial sculptures,’ an intriguing idea that seems to have influenced the artistic illustration accompanying the research announcement.

Artistic rendering live E.coli bacteria that have been shaped into a rectangle, triangle, circle, and square (from front to back). Colors indicate the density of the Min proteins that represent a snapshot in time (based on actual data), as these proteins oscillate back and forth within the bacterium, to determine the mid plane of the cell for cellular division. Image credit:  ‘Image Cees Dekker lab TU Delft / Tremani’

Artistic rendering live E.coli bacteria that have been shaped into a rectangle, triangle, circle, and square (from front to back). Colors indicate the density of the Min proteins that represent a snapshot in time (based on actual data), as these proteins oscillate back and forth within the bacterium, to determine the mid plane of the cell for cellular division.
Image credit: ‘Image Cees Dekker lab TU Delft / Tremani’

A June 22, 2015 news item on Nanowerk provides more insight into the research (Note: A link has been removed),

The E.coli bacterium, a very common resident of people’s intestines, is shaped as a tiny rod about 3 micrometers long. For the first time, scientists from the Kavli Institute of Nanoscience at Delft University have found a way to use nanotechnology to grow living E.coli bacteria into very different shapes: squares, triangles, circles, and even as letters spelling out ‘TU Delft’. They also managed to grow supersized E.coli with a volume thirty times larger than normal. These living oddly-shaped bacteria allow studies of the internal distribution of proteins and DNA in entirely new ways.

In this week’s Nature Nanotechnology (“Symmetry and scale orient Min protein patterns in shaped bacterial sculptures”), the scientists describe how these custom-designed bacteria still manage to perfectly locate ‘the middle of themselves’ for their cell division. They are found to do so using proteins that sense the cell shape, based on a mathematical principle proposed by computer pioneer Alan Turing in 1953.

A June 22, 2015 TU Delft press release, which originated the news item, expands on the theme,

Cell division

“If cells can’t divide properly, biological life wouldn’t be possible. Cells need to distribute their cell volume and genetic materials equally into their daughter cells to proliferate.”, says prof. Cees Dekker, “It is fascinating that even a unicellular organism knows how to divide very precisely. The distribution of certain proteins in the cell is key to regulating this, but how exactly do those proteins get that done?”

Turing

As the work of the Delft scientist exemplifies, the key here is a process discovered by the famous Alan Turing in 1953. Although Turing is mostly known for his role in deciphering the Enigma coding machine and the Turing Test, the impact of his ‘reaction-diffusion theory’ on biology might be even more spectacular. He predicted how patterns in space and time emerge as the result of only two molecular interactions – explaining for instance how a zebra gets its stripes, or how an embryo hand develops five fingers.

MinD and MinE

Such a Turing process also acts with proteins within a single cell, to regulate cell division. An E.coli cell uses two types of proteins, known as MinD and MinE, that bind and unbind again and again at the inner surface of the bacterium, thus oscillating back and forth from pole to pole within the bacterium every minute. “This results in a low average concentration of the protein in the middle and high concentrations at the ends, which drives the division machinery to the cell center”, says PhD-student Fabai Wu, who ran the experiments. “As our experiments show, the Turing patterns allow the bacterium to determine its symmetry axes and its center. This applies to many bacterial cell shapes that we custom-designed, such as squares, triangles and rectangles of many sizes. For fun, we even made ‘TUDelft’ and ‘TURING’ letters. Using computer simulations, we uncovered that the shape-sensing abilities are caused by simple Turing-type interactions between the proteins.”

Actual data for live E.coli bacteria that have been shaped into the letters TUDELFT.
The red color shows the cytosol contents of the cell, while the green color shows the density of the Min proteins, representing a snapshot in time, as these proteins oscillate back and forth within the bacterium to determine the mid plane of the cell for cellular division. The letters are about 5 micron high.
Image credit:  ‘Fabai Wu, Cees Dekker lab at TU Delft’

Spatial control for building synthetic cells

“Discovering this process is not only vital for our understanding of bacterial cell division – which is important in developing new strategies for antibiotics. But the approach will likely also be fruitful to figuring out how cells distribute other vital systems within a cell, such as chromosomes”, says Cees Dekker. “The ultimate goal in our research is to be able to completely build a living cell from artificial components, as that is the only way to really understand how life works. Understanding cell division – both the process that actually pinches off the cell into two daughters and the part that spatially regulates that machinery – is a major part of that.”

Here’s a link to and a citation for the paper,

Symmetry and scale orient Min protein patterns in shaped bacterial sculptures by Fabai Wu, Bas G. C. van Schie, Juan E. Keymer, & Cees Dekker. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.126 Published online 22 June 2015

This paper is behind a paywall but there does seem to be another link (in the excerpt below) which gives you a free preview via ReadCube Access (according to the TU Delft press release),

The DOI for this paper will be 10.1038/nnano.2015.126. Once the paper is published electronically, the DOI can be used to retrieve the abstract and full text by adding it to the following url: http://dx.doi.org/

Enjoy!

New molecular ruler could help with developing antibiotics

Researchers at the University of Utah have developed a molecular ruler which could help to determine the length at which a nanoscale needle is effective. From a March 17, 2015 news item on Azonano,

When a salmonella bacterium attacks a cell, it uses a nanoscopic needle to inject it with proteins to aid the infection. If the needle is too short, the cell won’t be infected. Too long, and the needle breaks. Now, University of Utah biologists report how a disposable molecular ruler or tape measure determines the length of the bacterial needle so it is just right.

The findings have potential long-term applications for developing new antibiotics against salmonella and certain other disease-causing bacteria, for designing bacteria that could inject cancer cells with chemotherapy drugs, and for helping people how to design machines at the nanoscopic or molecular scale.

A March 16, 2015 University of Utah news release, which originated the news item, provides some insight from the researchers,

“If you look at important pathogens – the bubonic plague bacterium, salmonella, shigella and plant pathogens like fire blight – they all use hypodermic-like needles to inject proteins that facilitate disease processes,” Hughes [University of Utah biology professor Kelly Hughes] says.

“Our work says that there is one mechanism – the molecular ruler – to explain how the lengths are controlled for needles in gram-negative bacteria and for hooks on flagella [the U-joints in propellers bacteria use to move] in all bacteria,” he adds.

In their study, Wee [University of Utah doctoral student Daniel Wee] and Hughes found that as a bacterial needle or “injectisome” grows, a molecular ruler – really, more like a gooey tape measure – is secreted from within the needle’s base. It oozes up through the tube-like needle, and when the bottom end of the ruler reaches the bottom end of the needle, the needle stops growing and begins to inject proteins into the target cell to help the infection process.

The biologists say the [US] National Institutes of Health-funded study refutes other theories for how salmonella and some other disease bacteria determine needle lengths.

The news release also explains how this finding could be made useful,

“What we understand from bacteria can help us build nanomachines and nanobots,” Hughes says, noting that bacterial flagella – the nanoscopic motor-and-propeller system they use to swim to dinner or to targets – are “the most sophisticated nanomachines in the universe.”

In one example, Swiss scientists are using the design of bacterial flagella as the basis for a nanobot that will be put inside the eye to do nanoscale surgery, he adds.

In addition to flagella, a number of disease-causing bacteria also have injectisomes, which also are built of proteins, as are most structures in living organisms.

“In the case of the needle, you have a structure that extends from the surface of the bacterium like a hypodermic,” Hughes says. “These needles are fragile. If one is too long, it will break off and be useless. If you make it too short, then it can’t get past the surface proteins on cells it needs to invade.”

By understanding how bacteria determine the length for their needles, it someday may be possible to engineer bacteria to inject chemotherapy drugs right into cancer cells.

“People would like to design bacteria that can get to cancer cells and inject poisons into just those cells and kill them, and not harm the rest of us,” Hughes says.

And by understanding how certain disease-causing bacteria build their injectisomes, new antibiotics might be developed in a decade or so to target and destroy the needles and thus deter bacterial infections. The rulers that help build flagella also might be attacked by drugs to prevent bacteria from reaching target cells, “so you can kill two birds with one stone by hitting the two machines at the same time,” Hughes says.

He says that approach might work against injectisome-equipped bacteria such as salmonella species that cause typhoid fever and food poisoning; shigella species that cause dysentery; the bubonic plague bacterium Yersinia pestis; disease-causing E. coli; sexually transmitted Chlamydia trachomatis; many plant pathogens; and Pseudomonas aeruginosa, which often infects burn patients and the lungs of cystic fibrosis patients.

Not usually my kind of thing, I find this quite fascinating (from the news release),

Bacteria secrete a molecular ruler to measure needle length

Bacterial injectisomes are incredibly small, measuring only 20 to 100 nanometers long. A nanometer is one billionth of a meter, and a meter is about 39 inches long. The width of a typical human hair often is given as 100 microns, so the maximum length of a bacterial needle, 100 nanometers, is one-thousandth of the width of a human hair.

Gram-negative, disease-causing bacteria “are very closely related species, so how do they subtly control the various needle lengths to be perfect?” Hughes asks. “In one case it might be 40 nanometers versus 55 nanometers. These are small sizes. So to do this, the bacteria developed molecular rulers to differentiate needles of different lengths.”

(Gram-negative bacteria are those with membranes lining both the inside and outside of their cell wall, while gram-positive bacteria have only an inner membrane.)

Like any cell, a bacterium is encased in a cell wall. So bacteria developed all kinds of secretions to make contact with and infect other cells: flagellar propellers to swim to food or target cells, docking structures to help bacteria stick to targets, and injectisomes to inject infection-promoting proteins into targets.

When a bacterium builds a needle, it first builds a base. “A series of proteins form a doughnut, and inside the doughnut hole, the actual secretion machine gets constructed,” Hughes says. “It’s the same for the flagella as it is for these needles.”

Next, proteins start assembling to form the needle or injectisome.

The new study demonstrated that in salmonella, the ruler or tape measure is secreted slowly through the channel of the growing needle. Once amino acids at the bottom end of the ruler pass through the base of the needle, they tell the bacterium that the needle is long enough and to stop growing. They also tell the needle to injecting virulence proteins into the target cell, and the molecular ruler is ejected, Wee says.

Here’s an image of what the injectisome looks like,

On the left is an electron microscope image of an injectisome, the nanoscopic needle that salmonella and certain other bacteria use to inject proteins into target cells as part of the infection process. The illustration at center depicts the exterior of the needle and its base. The cross-section at right shows the string-like molecular ruler that determines the length of salmonella’s bacteria needle, according to a new University of Utah study by doctoral student Daniel Wee and biology professor Kelly Hughes. Credit: Daniel Wee, University of Utah

On the left is an electron microscope image of an injectisome, the nanoscopic needle that salmonella and certain other bacteria use to inject proteins into target cells as part of the infection process. The illustration at center depicts the exterior of the needle and its base. The cross-section at right shows the string-like molecular ruler that determines the length of salmonella’s bacteria needle, according to a new University of Utah study by doctoral student Daniel Wee and biology professor Kelly Hughes. Credit: Daniel Wee, University of Utah

The news release also offers some specific details about the research,

How the study was performed

The new study used the Typhimurium strain of Salmonella enterica, which causes food poisoning. The researchers proved the molecular ruler determines needle length in salmonella by inserting amino acids from the plague bacterium’s molecular ruler genes into genes for salmonella’s molecular ruler, making rulers with seven different lengths.

Genetically engineered salmonella with seven ruler lengths were grown in a flask, their needles isolated, and the needle lengths measured under an electron microscope.

Wee found the ruler lengths correlated precisely with the lengths of the resulting needles or injectisomes, with each amino acid added to the ruler gene making the resulting needle 0.2 nanometers longer.

Previous studies found the molecular ruler determines the length of the hook or U-joint that helps turn flagella or propellers in many bacteria. Research also found the molecular ruler determines the length of both the flagellar hook and the needle in plague bacteria. But some researchers argued salmonella needle’s length was determined by some other mechanism:

– One theory holds that a molecular measuring cup in the needle’s base sends a cupful of needle components to assemble the needle, and the length of the needle is determined by the size of the cup. The new study disproved that by genetically removing the cup and showing that the injectisomes or needles still grew to correct lengths.

– Another theory says that as needle components assemble outside the needle’s base, a rod-shaped structure assembles inside the base to link the base and needle, and that when the rod is complete, needle assembly stops, thus determining needle length. But the Utah study found the rod and needle components are not made simultaneously, but compete with each other, so as more rod parts are made, fewer needle parts are made, giving an illusion that rod completion controls needle length.

Here’s a link to and a citation for the paper,

Molecular ruler determines needle length for the Salmonella Spi-1 injectisome by Daniel H. Wee and Kelly T. Hughes. Published online before print March 16, 2015, doi: 10.1073/pnas.1423492112 PNAS March 16, 2015

This paper is behind a paywall.