Phenotypic heterogeneity and the evolution of metabolic cross-feeding interactions

点击翻译按钮获取中文摘要

Cooperative cross-feeding, in which two or more individuals exchange costly metabolites, is very common in the microbial world. However, a release of metabolites into the external environment is difficult to reconcile with natural selection: selfish mutants are expected to evolve and exploit the public good without reciprocating, thus threatening the integrity of these cooperative interactions. Previous work of the applicant has shown that cooperative cross-feeding interactions rapidly evolved among two Escherichia coli genotypes that were auxotrophic for two different amino acids. After only 8 weeks of coculture, auxotrophic consortia gained a significant increase in fitness, which was due to enhanced amino acid production levels. Interestingly, derived consortia consistently showed an extensive degree of phenotypic heterogeneity, which coincided with the formation of multicellular clusters. Hypothesizing that selection on a between-cluster level caused this pattern, the proposed project aims at identifying the biological significance of the observed heterogeneous populations. For this, pairs of auxotrophic genotypes belonging to one of three bacterial species will be assembled. Experimental coevolution of the resulting intra- and inter-specific combinations will allow to determine the impact of genetic relatedness on the formation of multicellular clusters and identify the role the generation of phenotypic heterogeneity plays during this process. By combining individual-based modelling, microscopic analyses on a single-cell level, and a detailed investigation of derived phenotypes, unprecedented mechanistic insights into the dynamics that shape the evolution of cooperative cross-feeding interactions can be gained.