Microbial individuality: how single-cell heterogeneity enables population level strategies

• Gene expression can be surprisingly dynamic and noisy.
• Cell to cell heterogeneity in gene expression state is a widespread phenomenon.
• Phenotypic diversity can be generated by both stochastic and deterministic mechanisms.
• Phenotypic diversity can implement population level functions.

Much of our knowledge of microbial life is only a description of average population behaviours, but modern technologies provide a more inclusive view and reveal that microbes also have individuality. It is now acknowledged that isogenic cell-to-cell heterogeneity is common across organisms and across different biological processes. This heterogeneity can be regulated and functional, rather than just reflecting tolerance to noisy biochemistry. Here, we review recent advances in our understanding of microbial heterogeneity, with an emphasis on the pervasiveness of heterogeneity, the mechanisms that sustain it, and how heterogeneity enables collective function.