Bacterial cooperation through horizontal gene transfer
Authors: Isaiah Paolo A. Lee, Omar Tonsi Eldakar, J. Peter Gogarten, Cheryl P. Andam
Journal: Trends in Ecology & Evolution (2021)

Cooperation is ubiquitous in bacterial populations. Bacteria produce and share public goods, providing indiscriminate benefits to their neighbors at cost to themselves.Bacteria often engage in horizontal gene transfer (HGT) to rapidly disseminate traits in a population. HGT provides an important mechanism for cooperation to spread, effectively acting as an enforcement mechanism.Public goods can also promote HGT, potentially resulting in positive feedback loops between the two.HGT could itself be considered a public good due to the costly benefits it provides a population. Cooperation exists across all scales of biological organization, from genetic elements to complex human societies. Bacteria cooperate by secreting molecules that benefit all individuals in the population (i.e., public goods). Genes associated with cooperation can spread among strains through horizontal gene transfer (HGT). We discuss recent findings on how HGT mediated by mobile genetic elements promotes bacterial cooperation, how cooperation in turn can facilitate more frequent HGT, and how the act of HGT itself may be considered as a form of cooperation. We propose that HGT is an important enforcement mechanism in bacterial populations, thus creating a positive feedback loop that further maintains cooperation. To enforce cooperation, HGT serves as a homogenizing force by transferring the cooperative trait, effectively eliminating cheaters. Cooperation exists across all scales of biological organization, from genetic elements to complex human societies. Bacteria cooperate by secreting molecules that benefit all individuals in the population (i.e., public goods). Genes associated with cooperation can spread among strains through horizontal gene transfer (HGT). We discuss recent findings on how HGT mediated by mobile genetic elements promotes bacterial cooperation, how cooperation in turn can facilitate more frequent HGT, and how the act of HGT itself may be considered as a form of cooperation. We propose that HGT is an important enforcement mechanism in bacterial populations, thus creating a positive feedback loop that further maintains cooperation. To enforce cooperation, HGT serves as a homogenizing force by transferring the cooperative trait, effectively eliminating cheaters. Cooperation has evolved many times across the Tree of Life and at all levels of biological organization, from genes forming genomes, to cells forming multicellular organisms, to eusocial insects forming superorganisms, and even to different species forming communities [1.West S.A. et al.Evolutionary explanations for cooperation.Curr. 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The complexity of microbial communities might therefore promote plasmid persistence because of multiple sources and sinks of plasmid transfer [59.Li L. et al.Plasmids persist in a microbial community by providing fitness benefit to multiple phylotypes.ISME J. 2020; 14: 1170-1181Crossref PubMed Scopus (13) Google Scholar,67.Hall J.P.J. et al.Source-sink plasmid transfer dynamics maintain gene mobility in soil bacterial communities.Proc. Natl. Acad. Sci. U. S. A. 2016; 113: 8260-8265Crossref PubMed Scopus (60) Google Scholar,68.Alonso-Del Valle A. et al.Variability of plasmid fitness effects contributes to plasmid persistence in bacterial communities.Nat. Commun. 2021; 12: 2653Crossref PubMed Scopus (12) Google Scholar].Box 1Dynamics of public good genes in structured populationsSince the inception of evolutionary game theory, stable cooperation has been associated with population structure [78.Hamilton W.D. The genetical evolution of social behaviour. I.J. Theor. 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