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Bacteria coordinate their social behavior in a density dependent manner by production of diffusible signal molecules by a process known as quorum sensing (QS). It is generally assumed that in homogenous environments and at high cell density, QS synchronizes cells in the population to perform collective social tasks in unison which maximize the benefit at the inclusive fitness of individuals. However, evolutionary theory predicts that maintaining phenotypic heterogeneity in performing social tasks is advantageous as it can serve as bet9 hedging survival strategy under changing environmental condition. Using Pseudomonas syringae and Xanthomonas campestris as model organisms, which use two diverse classes of QS signals, we show that two distinct subpopulations of QS-responsive and non-responsive cells exist in the QS-activated population. Addition of excess exogenous QS signal does not significantly alter the bimodal distribution of QS-responsive and non-responsive cells in the population. We further show that progeny of cells derived from these subpopulations also exhibited heterogeneous distribution patterns similar to their respective parental strains. Such a pattern is in contrast to non-reversible genetic heterogeneity where the spontaneous occurrence of social cheaters in the QS-responding population would be selected. Co-migration experiments indicated that QS- cells in a mixed population have the advantage in migration and spread. Overall, these results support the model that bacteria maintain QS-responsive and non-responsive subpopulations at high cell densities that a bet-hedging strategy to simultaneously perform functions that are both positively and negatively regulated by QS to have better fitness in fluctuating environment.

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This page is a summary of: Reversible non-genetic phenotypic heterogeneity in bacterial quorum sensing, Molecular Microbiology, April 2014, Wiley,
DOI: 10.1111/mmi.12575.
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