Explaining natural wonders: bacterial intelligence (Animals)

by David Turell @, Thursday, May 18, 2017, 18:43 (126 days ago) @ dhw


dhw: I have said repeatedly that bacterial intelligence is crucial to the hypothesis of the autonomous (i.e. without divine instructions/guidelines) inventive mechanism as a driving force for evolution,

I've tried to explain why I know bacteria are basically automatic. Let us look at bacterial chemotaxis:

http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0020049

"we propose what is to our knowledge the first computational model for B. subtilis chemotaxis and compare it to previously published models for chemotaxis in E. coli. The models reveal that the core control strategy for signal processing is the same in both organisms, though in B. subtilis there are two additional feedback loops that provide an additional layer of regulation and robustness. Furthermore, the network structures are different despite the similarity of the proteins in each organism. These results demonstrate the limitations of pathway inferences based solely on homology and suggest that the control strategy is an evolutionarily conserved property.

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"Chemotaxis is the process by which motile bacteria sense changes in their chemical environment and move to more favorable conditions . In peritrichously flagellated bacteria such as Escherichia coli and Bacillus subtilis, swimming alternates between smooth runs and reorientating tumbles. Smooth runs require that the flagellar motors spin counterclockwise, whereas tumbles result from clockwise spins. Bacteria follow a random walk that is biased in the presence of gradients of attractants and repellents by alternating the frequency of runs and tumble. Owing to their small size, most bacteria are unable to sense chemical gradients across the length of their body. Rather, they respond only to temporal changes. In particular, their stimulated response always returns to prestimulus levels despite the sustained presence of attractants or repellents. Sensory adaptation involves a rudimentary form of memory that allows bacteria to compare their current and past environments. Bacteria regulate chemotaxis using a network of interacting proteins. The basic mechanism in flagellated bacteria involves receptor-mediated phosphorylation of a cytoplasmic protein (CheY) that binds to the flagellar motor and changes the spin direction (Falke et al. 1997). This pathway is characterized best in the γ-proteobacteria—E. coli and Salmonella enterica serovar typhimurium.

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" By constructing a model of B. subtilis chemotaxis and comparing it to models of E. coli chemotaxis, we were able to explore two mechanisms for sensory adaptation involving homologous genes. These models enabled us to interpret a large class of data involving many different experimental conditions and mutants. The conclusion from this theoretical study is that both networks involve the same core control process, though the physical interactions and feedback loops that form this process are different."

Comment: It is worth looking at the complex biochemical pathways that this study illustrates. Note the mention of feedback loop controls. The only mentation is a chemical semi-memory of past stimuli to allow some choices which, if you note carefully, are temporal along the length of their bodies!


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