Massive Diversification in Aging Colonies of Escherichia coli

Abstract

The evolutionary success of bacteria depends greatly on their capacity to continually generate phenotypic diversity. Structured environments are particularly favorable for diversification because of attenuated clonal interference, which renders selective sweeps nearly impossible and enhances opportunities for adaptive radiation. We examined at the microscale level the emergence and the spatial and temporal dynamics of phenotypic diversity and their underlying causes in Escherichia coli colonies. An important dynamic heterogeneity in the growth, metabolic activity, morphology, gene expression patterns, stress response induction, and death patterns among cells within colonies was observed. Genetic analysis indicated that the phenotypic variation resulted mostly from mutations and that indole production, oxidative stress, and the RpoS-regulated general stress response played an important role in the generation of diversity. We observed the emergence and persistence of phenotypic variants within single colonies that exhibited variable fitness compared to the parental strain. Some variants showed improved capacity to produce biofilms, whereas others were able to use different nutrients or to tolerate antibiotics or oxidative stress. Taken together, our data show that bacterial colonies provide an ecological opportunity for the generation and maintenance of vast phenotypic diversity, which may increase the probability of population survival in unpredictable environments.

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

“…Such 'division of labour' [24 ] underlies the formation and maintenance of biofilms (Figure 1h-j), which are highly heterogeneous in space and time [50][51][52], and the dynamics of infection by Salmonella typhimurium (in which division of labour can, in fact, occur in conjunction with bet hedging) [24 ]. These examples bridge the conceptual gap between unicellular and higher organisms, and demonstrate how microbes explore cell-to-cell heterogeneity to flirt with multicellularity.…”

Cell rejuvenation and social behaviors promoted by LPS exchange in myxobacteria

“…These behaviors require contributions from many individuals and thus are threatened by heterogeneity among members. Such heterogeneity might develop both from individual cells being exposed to different microenvironments present in the soil (8) and from diversity in cell ages (9). Thus, starving or damaged members of a population bear a damage burden for the community that, when prevalent, could be detrimental to group behaviors.…”

The fitness change and the diversity maintenance in the growing mixed colony of two Serratia rubidaea clones

“…The large genetic variability is generated during the growth and mutants may have different fitness and may appear also as radial colony patterning (Saint-Ruf et al 2014). In that case, the radial structures will start not only in the inoculum but also in the whole area of the growing colony.…”