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Gene flux and chromosomal recombination as key drivers of adaptability and population functioning of Streptomyces

Abstract : Unlike most bacteria, Streptomyces have a linear chromosome (6-12 Mb). The chromosome arms are highly recombinogenic, promoting the formation of large rearrangements, including deletions that can cause the loss of up to a quarter of the chromosome in a single event, and high intensity gene amplifications. While these rearrangements have revealed the compartmentalization of the genome with essential genes at the center of the chromosome and dispensable genes in the arms, the contribution of genome rearrangements to the evolutionary mechanisms and biology of the organism has long been debated. Comparative genomics approaches have recently demonstrated that increased recombination in the chromosomal arms contributes to genetic diversification both at the level of the bacterial population (Tidjani et al., 2019, 2020) and of the bacterial genus as a whole (Lorenzi et al., submitted). At the genus level, diversification involves an increasing gradient of horizontal transfer and genomic rearrangement events towards the ends of the chromosome. At the population level, analysis of closely related strains (rDNA 16S 100% identical) confirmed this phenomenon by revealing early events occurring during diversification. The absence of natural transformation or transducing phages suggests that diversification results from conjugative transfer. Indeed, actinomycetes genomes revealed an important wealth in integrated and conjugative elements. We have also shown that genomic diversity contributes to the functioning of the Streptomyces population in the micro-habitat, promoting the production of common goods by a fraction of the population (Tidjani et al., 2019). This result is further supported by the demonstration by D. Rozen's team (Uni. Leiden) that within a colony, the presence of mutants with rearranged chromosomes influences the antibiotic production capacity of the entire population (Zhang et al., 2020). Altogether, these results show that the ability to rearrange its genome allows Streptomyces to diversify its genome content and could contribute to its adaptability to the soil, which is a naturally challenging ecosystem.
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https://hal.univ-lorraine.fr/hal-03059295
Contributor : Pierre Leblond <>
Submitted on : Monday, December 14, 2020 - 6:49:09 PM
Last modification on : Monday, May 3, 2021 - 5:04:03 PM

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Pierre Leblond. Gene flux and chromosomal recombination as key drivers of adaptability and population functioning of Streptomyces. Actino 2020 Journées des actinobactéries (en ligne), Dec 2020, Paris, France. ⟨hal-03059295⟩

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