Project Details
Projekt
Altruistic suicide in multicellular clusters of bacteria: causes and consequences
Subject Area
Microbial Ecology and Applied Microbiology
Metabolism, Biochemistry and Genetics of Microorganisms
Metabolism, Biochemistry and Genetics of Microorganisms
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 504072468
Bacteria mainly occur within surface-attached or free-floating multicellular groups. These spatially structured communities commonly display behaviours that are beneficial to the group, yet costly to the acting individual cell. One of these behaviours is the altruistic suicide of cells that has been suggested to benefit cellular aggregates by providing nutrients to clonemates or facilitating dispersal of clusters. While several causal genes have been identified, knowledge on the evolutionary conditions favouring programmed cell death in bacteria remains rudimentary. One reason for this is the lack of techniques that allow to observe and analyse bacterial groups with single-cell resolution, which is crucial to investigate the ecological consequences of cell lysis. This project aims at addressing this issue. We will take advantage of a model system, in which two auxotrophic genotypes of Escherichia coli, which could only grow when reciprocally exchanging essential amino acids, were serially propagated. Over the course of only 150 generations, coevolved strains became more cooperative as evidenced by drastically increased amino acid production levels relative to ancestral strains. The evolution of mutualistic cooperation was due to the formation of multicellular clusters that benefitted cooperative mutants within clusters. Interestingly, lineages evolved a life cycle, in which cells switched between a unicellular and a multicellular cluster-stage. Moreover, this pattern correlated with the proportion of dead cells that increased over the course of the evolution experiment. Our project aims at identifying the molecular drivers of cell lysis as well as at unravelling the evolutionary consequences for multicellular clusters. For this, we will combine transcriptomic analyses of mutants carrying previously identified mutations with carefully designed coculture experiments. In addition, we will develop a novel microfluidic platform to grow, observe, and analyse three-dimensional multicellular clusters with single-cell resolution. By identifying the molecular causes and eco-evolutionary consequences of cell lysis in bacteria, our project will contribute to a better understanding of this widespread group-level behaviour.
DFG Programme
Priority Programmes
