Xenobots (living robots made from African frog (Xenopus laevis) frog cells) can now self-replicate. First mentioned here in a June 21, 2021 posting, xenobots have captured the imagination of various media outlets including the Canadian Broadcasting Corporation’s (CBC) Quirks and Quarks radio programme and blog where Amanda Buckiewicz posted a December 3, 2021 article about the latest xenobot development (Note: Links have been removed),
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In a new study, Bongard [Joshua Bongard, a computer scientist at the University of Vermont] and his colleagues from Tufts University and Harvard’s Wyss Institute for Biologically Inspired Engineering found that the xenobots would autonomously collect loose single cells in their environment, gathering hundreds of cells together until new xenobots had formed.
“This took a little bit for us to wrap our minds around,” he said. “There’s no programming here. Instead, we’re designing or shaping these xenobots, and what they do, the way they behave, is based on shape.”
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“We take a couple of thousand of those frog cells and we squish them together into a ball and put that in the bottom of a petri dish,” Bongard told Quirks & Quarks host Bob McDonald.
“If you were to look into the dish, you would see some very small, what look like specks of pepper, moving about in the bottom of the petri dish.”
The xenobots initially received no instruction from humans on how to replicate. But when researchers added extra cells to the dish containing xenobots, they observed that the xenobots would assemble them into piles.
“Cells early in development are sticky,” said Bongard. “If the pile is large enough and the cells stick together, the outer ones on the surface will grow very small hairs, which are called cilia. And eventually, after four days, those cilia will start to beat back and forth like flexible oars, and the pile will start moving.”
“And that’s a child xenobot.”
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A November 29, 2021 Wyss Institute news release by Joshua Brown describes the process a little differently,
To persist, life must reproduce. Over billions of years, organisms have evolved many ways of replicating, from budding plants to sexual animals to invading viruses.
Now scientists at the University of Vermont, Tufts University, and the Wyss Institute for Biologically Inspired Engineering at Harvard University have discovered an entirely new form of biological reproduction—and applied their discovery to create the first-ever, self-replicating living robots.
The same team that built the first living robots (“Xenobots,” assembled from frog cells—reported in 2020) has discovered that these computer-designed and hand-assembled organisms can swim out into their tiny dish, find single cells, gather hundreds of them together, and assemble “baby” Xenobots inside their Pac-Man-shaped “mouth”—that, a few days later, become new Xenobots that look and move just like themselves.
And then these new Xenobots can go out, find cells, and build copies of themselves. Again and again.
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In a Xenopus laevis frog, these embryonic cells would develop into skin. “They would be sitting on the outside of a tadpole, keeping out pathogens and redistributing mucus,” says Michael Levin, Ph.D., a professor of biology and director of the Allen Discovery Center at Tufts University and co-leader of the new research. “But we’re putting them into a novel context. We’re giving them a chance to reimagine their multicellularity.” Levin is also an Associate Faculty member at the Wyss Institute.
And what they imagine is something far different than skin. “People have thought for quite a long time that we’ve worked out all the ways that life can reproduce or replicate. But this is something that’s never been observed before,” says co-author Douglas Blackiston, Ph.D., the senior scientist at Tufts University and the Wyss Institute who assembled the Xenobot “parents” and developed the biological portion of the new study.
“This is profound,” says Levin. “These cells have the genome of a frog, but, freed from becoming tadpoles, they use their collective intelligence, a plasticity, to do something astounding.” In earlier experiments, the scientists were amazed that Xenobots could be designed to achieve simple tasks. Now they are stunned that these biological objects—a computer-designed collection of cells—will spontaneously replicate. “We have the full, unaltered frog genome,” says Levin, “but it gave no hint that these cells can work together on this new task,” of gathering and then compressing separated cells into working self-copies.
“These are frog cells replicating in a way that is very different from how frogs do it. No animal or plant known to science replicates in this way,” says Sam Kriegman, Ph.D., the lead author on the new study, who completed his Ph.D. in Bongard’s lab at UVM and is now a post-doctoral researcher at Tuft’s Allen Center and Harvard University’s Wyss Institute for Biologically Inspired Engineering.
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Both Buckiewicz’s December 3, 2021 article and Brown’s November 29, 2021 Wyss Institute news release are good reads with liberal used of embedded images. If you have time, start with Buckiewicz as she provides a good introduction and follow up with Brown who gives more detail and has an embedded video of a December 1, 2021 panel discussion with the scientists behind the xenobots.
Here’s a link to and a citation for the latest paper,
Kinematic self-replication in reconfigurable organisms by Sam Kriegman, Douglas Blackiston, Michael Levin, and Josh Bongard. PNAS [Proceedings of the National Academy of Sciences] December 7, 2021 118 (49) e2112672118; https://doi.org/10.1073/pnas.2112672118
This paper appears to be open access.