tag > ALife
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There's a bacteriophage that turns bacteria into “liquid crystals.”
Specifically, Pseudomonas aeruginosa bacteria make Pf phages, which are rod-shaped, negatively-charged, and measure about 2 micrometers in length (roughly the length of an E. coli cell). These phages leave the cells and enter their surroundings. There, they mix with polymers, also secreted by the cells, to form a crystalline matrix.
Surprisingly, this is good for the cells. Although the phages kill some of them, it also makes their biofilms stickier and able to withstand certain antibiotics. These bacteria + phages are prevalent in cystic fibrosis patients; they've formed a sort of symbiotic relationship.
The Pf phages are made from thousands of repeating copies of a coat protein, called CoaB, which wraps around a single-stranded, circular DNA genome. These genes are integrated directly on the bacterial chromosome.
The bacteria “turn on” these phage genes when placed in a viscous environment with low oxygen levels. This is like a trigger to start forming a biofilm. And the cells make a lot of phages; about 100 billion per milliliter.
These liquid crystals form because of a physics principle called “depletion attraction.” If you just mix a bunch of loose or flexible polymers together (such as long carbon chains) they will not form a liquid crystal. But if you mix stiff rods (the phages) with loose polymers at a high enough concentration, the polymers will force the phages close together to create a material that flows like a liquid despite being ordered like a crystal. See the video below.
These liquid crystal biofilms are hard to get rid of. The negatively-charged phages block many antibiotics (like aminoglycosides, which are positively-charged) from entering cells. Liquid crystals also retain water, so these biofilms can survive on drier surfaces.
Paper: Filamentous Bacteriophage Promote Biofilm Assembly and Function
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"Although Max Delbrück held some anti-reductionist views; he conjectured that ultimately a paradox—akin perhaps to the waveparticle duality of physics—would be revealed about life."
Max Debrück and some members of the Phage group at Caltech in 1949.
Interview with Delbrück, 1980
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I just met Denis Noble at the royal institute last week and heard his fascinating short lecture on "Chemistry of Life begins with Water"
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Information Mechanics, Programmable matter, Reversible Computing and Cellular Automata - The life of Tommaso Toffoli & Norman Margolus
Two Papers, of countless: Programmable matter: Concepts and realization - Tommaso Toffoli, Norman Margolus (1991) - Programmable matter methods - Tommaso Toffoli (1999)
Recent Talks by the giants in the field:
The gift of invertibility, in math, physics, and cellular automata by Tommaso Toffoli (2024)
Information Mechanics: Then and Now by Norman Margolus (2024)
#ML #Technology #Science #Complexity #ALife #Biology #NeuroScience
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"The Simsulator: An interactive evolved virtual creature testbed" (Code)
31 years after Karl Sims' legendary work, the creatures are finally evolving again — and now you can run it at home. A dream of mine for over a decade.
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Eating gamma radiation for breakfast: Some fungal species appear to be able to use strong radiation as an energy source for growth.
Could the fungi be using the extremely high-energy gamma radiation as an energy source in the same way that plants use sunlight?
The key to it all seemed to be melanin – the ubiquitous group of pigments found in many types of eukaryote that protect against UV radiation
Many fungal fossils show evidence of melanisation, especially in periods of high radiation when many animal and plant species died out
Could you replace them with plants or fungi that use melanin instead of chlorophyll?
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Organism feeds upon is negative entropy
“What an organism feeds upon is negative entropy. Or, to put it less paradoxically, the essential thing in metabolism is that the organism succeeds in freeing itself from all the entropy it cannot help produce while alive.” - Erwin Schrödinger, What is Life? (1943)
Entropy, the measure of a system’s thermal energy per unit temperature that is unavailable for doing useful work. Because work is obtained from ordered molecular motion, the amount of entropy is also a measure of the molecular disorder, or randomness, of a system.
“Entropy requires no maintenance.” — Robert Anton Wilson
