Phenotypic variation in bacteria: the role of feedback regulation

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Abstract
Even under laboratory conditions, bacteria often show a high degree of phenotypic variability — cells within an isogenic population displaying variable expression patterns. Positive feedback within a regulatory network has the potential to generate multistationarity — the possibility of a cell to switch between states. Bistability or multistability is the occurrence of two or more distinguishable phenotypes within the isogenic population. The ratio of cells within a specific cell state depends on the intrinsic properties of the switch and is often influenced and modulated by environmental signals. It was found that the molecular mechanism underlying phenotypic variation in a number of adaptive bacterial responses, such as competence and sporulation in Bacillus subtilis, is based on positive feedback. Many of the observed — but still unexplained — variable phenotypes reported within bacterial research are likely to originate from the feedback structure within the regulatory pathway. Phenotypic variability is a way to increase the fitness of the population, especially under fluctuating environmental conditions.