Bacterial cell differentiationenables population level survival strategies

Abstract

Clonal reproduction of unicellular organisms ensures the stable inheritance of genetic information. However, this means of reproduction lacks an intrinsic basis for genetic variation, other than spontaneous mutation and horizontal gene transfer. To make up for this lack of genetic variation, many unicellular organisms undergo the process of cell differentiationto achieve phenotypic heterogeneity within isogenic populations. Cell differentiationis either an inducible or obligate program. Induced cell differentiationcan occur as a response to a stimulus, such as starvation or host cell invasion, or it can be a stochastic process. In contrast, obligate cell differentiationis hardwired into the organism's life cycle. Whether induced or obligate, bacterial cell differentiationrequires the activation of a signal transduction pathway that initiates a global change in gene expression and ultimately results in a morphological change. While cell differentiationis considered a hallmark in the development of multicellular organisms, many unicellular bacteria utilize this process to implement survival strategies. In this review, we describe well-characterized cell differentiationprograms to highlight three main survival strategies used by bacteria capable of differentiation:(i) environmental adaptation, (ii) division of labor, and (iii) bet-hedging.