Figure 7.

Physiological adaptations to environmental fluctuations at the single-cell level. (A) Some microorganisms anticipate environmental change by sensing the occurrence of an environmental condition that reliably precedes the anticipated condition. Increased temperature is one such example. E.coli upregulates genes for anoxic conditions long before experiencing a decrease in oxygen concentration (Tagkopoulus, Liu and Tavazoie 2008). (B) Some single-cell physiologies that emerge in fluctuating environments are distinct from steady-state physiologies. Some may arise while following the steady-state model, if the environment fluctuates on timescales faster than cells can reach each physiological steady state. This produces mixed physiologies, with partial expression of genes associated with both steady states. Alternatively, some single-cell physiologies are novel fluctuation-adapted physiologies, induced by environmental fluctuations to provide a growth advantage when environments fluctuate at certain timescales.