Control theory clarifies how to analyze environmental fluctuations in relation to the design of sensors and response systems. Recent advances in deep learning studies of artificial intelligence focus on the architecture of regulatory wiring and the ways in which complex control networks represent and classify environmental states. I emphasize the similar design problems that arise in cellular evolution, control theory, and artificial intelligence. I connect those broad conceptual aspects to many testable hypotheses for bacterial uptake of vitamin B 12 , siderophores, and glycans.
K E Y W O R D Scontrol theory, corrinoids, deep learning, microbiome, phenotypic plasticity, public goods, Plastic response requires sensor arrays to perceive availability.Environmental perception must then be transduced through a regulatory network that integrates information and alters deployment of the receptor array. How do aspects of environmental fluctuation shape the evolutionary design of sensory perception and the regulatory control to achieve a conditional response?I discuss how perception, classification, and response through a network relate to recent breakthroughs in artificial intelligence, neural networks, and deep learning. Bacterial systems provide great opportunity to link conceptual aspects of evolutionary design and deep learning to hypotheses that can be tested by comparative genomics and by experimental laboratory studies.I synthesize aspects of receptor arrays for vitamin B 12 analogs, for siderophores, and for glycans. By considering these different cases together, deeper principles of receptor variety and specificity emerge.Here, I use the word "receptor" to include the various binding and transport processes that influence specificity and rate of uptake. Degnan, Barry, et al. (2014), estimate that the human microbiome contains more than 30 receptor families for uptake of B 12 -like corrinoid variants. Genomic analyses predict that a significant fraction of all bacteria and archaea require a corrinoid variant for growth, yet only a minority can produce corrinoids (Rodionov, Vitreschak, Mironov, & Gelfand, 2003;Zhang, Rodionov, Gelfand, & Gladyshev, 2009). Competition over corrinoid variants shapes the receptor arrays of individual species and the dynamics of bacterial communities.Siderophores are secreted molecules that bind free iron. Bacteria use siderophore receptors to take up the siderophore-iron complexes.Iron often sets a limiting resource for microbial growth. Thus, competitive and cooperative processes over siderophore uptake shape bacterial community dynamics (Chakraborty, Braun, Hantke, & Cornelis, 2013;Niehus, Picot, Oliveira, Mitri, & Foster, 2017;West, Diggle, Buckling, Gardner, & Griffin, 2007). Individual bacteria may secrete more than one type of siderophore, or none at all. Bacteria typically have uptake receptors tuned for their own secreted types. In addition, bacteria often express an array of siderophore uptake receptors for types produced by other species (Loper & Henkels, 1999). Bacte...