Chemosensory diversity is invariant to background stimuli in chemotactic E. coli

Non-genetic phenotypic diversity allows populations to hedge their bets when future conditions are uncertain. Could such diversity play a role in how chemotactic bacteria navigate complex chemical environments? Bacteria sense chemical attractants with highly cooperative arrays of receptors that modulate the activity of a kinase controlling flagellar rotation. Previous work from our lab demonstrated that variation in the degree of receptor cooperativity in a population of cells leads to variation in sensitivity to chemoattractant. But upon adaptation to a background stimulus, this variation is significantly reduced, effectively switching the population from a bet-hedging strategy to one where every cell is sensitive to the signal. Here, we explored how sensitivity to one stimulus varies in the presence of different background stimuli. We found that perfect adaptation to a chemoattractant that binds one receptor, does not affect the distribution of sensitivities to signals that bind other receptors. However, if the background chemoattractant binds the same receptor at the same site as the foreground, the mean sensitivity decreases, but the degree of cell-to-cell variability in sensitivity to the foreground remains unchanged. Thus, isogenic populations can switch between bet-hedging and exploitation independently for multiple signals.