Research news

Even bacteria favor their kin

Photo by: CDC

Publish Date: 09.12.2021

Category: Our contribution to sustainable development goals

Sustainable development goals: 3 Good health and well-being, 4 Quality education, 14 Life below water, 15 Life on land (Indicators)

Researchers at the Biotechnical Faculty, University of Ljubljana (UL BF), studied the role of kinship dependent relationships among bacteria in surface colonization.

Nepotism in the workplace and in politics is a common topic of sensationalist media interest. However, nepotism or kin discrimination is also present in many animal species; it serves to stabilize cooperative behaviours and consequently promotes progeny and species survival. Researchers at the Biotechnical Faculty, University of Ljubljana, have shown that kin discrimination also affects territorial exclusion during surface colonization in the environmentally and commercially important bacterium Bacillus subtilis.

Successful surface colonization requires bacterial cooperation, which is based on fair sharing of public goods. The results of this study showed that bacteria may help their most related strains, even if they themselves are immobile, while less related strains are excluded from cooperative swarms and thus prevented from gaining access to the exploitation of public goods. New knowledge about the interactions between microorganisms is essential for the development of effective probiotics and biopesticides.

The results of a study led by Barbara Kraigher, PhD, and Prof. Ines Mandić Mulec, PhD, in collaboration with Asst. Prof. Polonca Štefanič, PhD, and Master's student Monika Butolen, were presented in a reputable scientific publication, ISME Journal. Their article titled "Kin discrimination drives territorial exclusion during Bacillus subtilis swarming and restrains exploitation of surfactin" presents research on bacterial swarming, which is a long-known process of collective cell movement across semi-solid and solid surfaces. Barbara Kraigher, PhD, explains: "Bacterial swarming is an important and complex process, which is still a poorly understood example of bacterial cooperation." Prof. Ines Mandič Mulec, PhD, adds: “Swarming is an excellent model   of bacterial behaviour, in which the effect of kinship on social interactions among bacteria can be tested, e.g. in terms of cooperation vs. competition during the colonization of nutrient containing surfaces". This study showed that highly related (kin) bacteria cooperated and colonized a new surface as a group, while less related ones were mutually excluded. Overall, the work uncovers that kin discrimination contributes to the maintenance of cooperative behaviour and could shape the diversity of microbial communities through frequency-dependent competition for surfaces. Bacillus subtilis is a very important probiotic, a plant growth promoter and a biopesticide, so these findings are important for the development of new approaches to protect the health of plants, animals and humans.

Nepotizem pri bakterijah 3The above photos show the swarming of two mutually exclusive fluorescently marked bacteria (they were taken using a fluorescent stereomicroscope with 8x magnification). The outcome of competition for surface colonization depends on the initial ratio of two less related strains within the mixture – positive frequency dependence. Left: The red majority strain colonizes the entire territory. Middle: Each strain colonizes its own part of the territory. Right: The green majority strain colonizes the entire territory. Source

This study was financed by the Slovenian Research Agency (Research Programme P4-0116 and Projects J4-8228, J4 9302, and J4-1775) and its implementation was also made possible by the Infrastructural Centre for the Microscopy of Biological Samples.





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