Evolution can alter the composition of communities, but its effects are difficult to investigate in nature, as they begin to manifest only after long periods of time. However, the rapid pace of microbial reproduction makes it possible to observe evolution in the laboratory ‘in real time’, from one generation to the next.
“In studies focusing on microbiome, using synthetic microbial communities, as we did in this study, has opened up new avenues for investigating key questions related to complex communities,” says Professor Teppo Hiltunen from the University of Turku.
A study conducted at the University of Turku’s Department of Biology demonstrated that the evolution of a single species can alter the composition of an entire species community. The study monitored a microbial community composed of 23 bacterial species for four years. During the experiment, the researchers analysed the community's species composition and changes in bacterial genomes.
The study involved communities cultivated in a medium supplemented with the antibiotic streptomycin and a control medium without the antibiotic. The antibiotic rapidly restructured communities by favouring species resistant to it and reducing the abundance of more sensitive species. One bacterial species, however, developed resistance to the drug through a single mutation. This evolutionary change made that species more abundant, while affecting the abundance of the others. As a result, the composition of the community with the mutant shifted to a new state.
“Being able to precisely connect community-level change with one mutation that causes antibiotic resistance was particularly significant,” says Postdoctoral Researcher Mikko Kivikoski from the University of Helsinki.
The results show that the long-term dynamics of species communities cannot be understood solely through ecological interactions or environmental factors. Evolution can also shape community dynamics and stability. This observation helps to understand aspects such as the functioning of microbial communities and the consequences of antibiotic resistance.
Carried out by Professor Teppo Hiltunen’s research group at the University of Turku in collaboration with groups led by Professor Ville Mustonen at the University of Helsinki and Professor Lutz Becks at the University of Konstanz, the study was part of the Finnish Multidisciplinary Centre of Excellence in Antimicrobial Resistance Research ( FiMAR ) funded by the Research Council of Finland.
The findings were published in the Proceedings of the National Academy of Sciences (PNAS) journal.
Proceedings of the National Academy of Sciences
Experimental study
Lab-produced tissue samples
Evolution induced state shifts in a long-term microbial community experiment
27-May-2026