Abstract

According to the conventional view, the properties of an organism are a product of nature and nurture – of its genes and the environment it lives in. Recent experiments with unicellular organisms have challenged this view: genetically individuals living in homogeneous laboratory environments can have markedly different properties, and express different sets of genes. We are interested in the functional consequences of this variation in bacteria: is phenotypic heterogeneity sometimes beneficial, and does it provide microbes with new functionality in their natural environment? I will first present results that suggest that, for the majority of the genes in a bacterial genome, natural selection acts to reduce phenotypic variation. Then, I will present a few exception to this rule, and discuss how phenotypic variation in clonal populations of bacteria can promote interactions between individuals, lead to the division of labor, and allow clonal groups of bacteria to cope with envi ronmental uncertainty. Finally, I will present recent results that indicate that phenotypic heterogeneity in bacterial populations does not only arise through individual molecular decisions in single cells, but is also shaped by interactions between cells that impact the expression of their phenotype. The main conclusion from this work is that microbial individuality can provide groups of organisms with collective functionality.