Laboratory evolution of anticipatory gene regulation inEscherichia coli

Abstract

Environmental cues in an ecological niche are temporal. In response to these temporal cues, bacteria have been known to exhibit learning or conditioning, whereby they trigger response to a yet to appear cue, anticipating its actual arrival in the near future. Such an anticipatory response in known to enhance Darwinian fitness, and hence, is likely an important feature in the regulatory networks in microorganisms. However, the conditions under which an anticipatory response optimizes cellular fitness are not known. Nor has evolution of anticipatory regulation in laboratory conditions been experimentally demonstrated. In this work, we develop a quantitative model to study response of a population to two temporal environmental cues, and present the key variables in cellular physiology associated with response to the cues whose modulation is likely to lead to evolution of anticipatory regulatory response. We predict experimental conditions, which are likely to lead to demonstration of rewiring of regulation, and evolution of anticipatory response in bacterial populations. Using inputs from the modeling results, we evolve E. coli in alternating environments of the pentose sugar rhamnose and paraquat, which induces oxidative stress. We demonstrate that growth in this cyclical environment leads to evolution of anticipatory regulation. Thus, we argue that in niches where environmental stimuli have a cyclical nature, conditioning evolves in a population as an adaptive response.

Non-Canonical Aspects of Antibiotics and Antibiotic Resistance

“…The marRAB regulon and overlapping soxRS regulon of E. coli both confer multi-resistance [16]. -An "anticipatory gene regulation" that occurred when E. coli was grown in alternating media containing rhamnose and paraquat (a superoxide-generating agent) partially induced the soxRS regulon after exposure to rhamnose [74]; bacteria may encounter such cycling environments during infections.…”