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Bacteria also avoid DNA exchange among relatives

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Publish Date: 27.12.2021

Category: Outstanding research achievements, Our contribution to sustainable development goals

Sustainable development goals: 14 Life below water, 15 Life on land (Indicators)

Kin discrimination promotes the horizontal transfer of genes among less related strains of B. subtilis, whereby the evolution of genomes can be accelerated towards increased diversity.

Kin discrimination enables humans, animals and even bacteria to recognise their relatives, and therefore affects intraspecies social interactions. However, such interactions and their consequences are not well understood. A team of researchers from the Biotechnical Faculty, University of Ljubljana (Asst. Prof. Polonca Štefanič,  PhD, Asst. Katarina Belcijan, Asst. Barbara Kraigher, PhD, Prof. Rok Kostanjšek, PhD, Prof. Ines Mandić-Mulec, PhD), Penn State University (Prof. Jasna Kovač, PhD), University of København (Joseph Nesme, PhD, Jonas Stenløkke Madsen, PhD, Prof. Søren Johannes Sørensen, PhD) and University of Exeter (Prof. Michiel Vos, PhD) found that bacteria attack less related representatives of the same species, kill them and take on the DNA of the strain which has lost in the attack. 

DNA exchange also takes place among highly related strains within a species, but these do not attack each other and as a result of this there is a lower degree of gene exchange between them compared to less related strains. This is reminiscent of the avoidance of mating among related specimens, which is characteristic of both humans and animals (inbreeding avoidance), but has not yet been detected in bacteria.

The key finding of this study is that there is an increased transfer of DNA among less related strains, which can accelerate the evolution of genomes towards increased diversity. This is because to date it has been considered that in bacteria transfer of DNA is greater among close relatives within a species, although different from the study done by the Biotechnical Faculty, University of Ljubljana such studies did not include the effect of bacterial interaction on horizontal gene transfer.

This study is extremely important, since it places the evolution of organisms from which all other living beings have developed in the context of social interactions. Furthermore, it reveals that in the horizontal transfer of genes, which is becoming one of the greatest medical problems for humankind, account also needs to be taken of the interactions among microbes as a driver of gene transfer and consequently the evolution of species.

For the first time, the study also reveals unequivocally that less related strains within a species kill each other, which is important to consider in the preparation of organic fertilisers and probiotics composed of several different strains. These interactions can indeed affect the composition and effectiveness of such preparations, and consequently the use value and costs of their manufacture.

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Figure: Kin discrimination affects DNA transfer by activating competence genes. Top: Kin (blue) and non-kin (red) interaction on semi-solid agar culture medium; Bottom left: DNA transfer between kin strains (blue) and non-kin strains (red); Bottom right: The activation of competence genes is greater when the interaction involves non-kin strains (red) compared to kin strains (blue). Author: Polonca Štefanič


Kin discrimination promotes horizontal gene transfer between unrelated strains in Bacillus subtilis. Nature communications. 2021, vol. 12, pp. 1-11,, DOI: 10.1038/s41467-021-23685-w.

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