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The role of the microbial community in evolutionary dynamics

In bacteria, a number of evolutionary forces are known to select for or against mutations. European researchers set out to understand whether the same criteria apply in the natural environment.
The role of the microbial community in evolutionary dynamics
In naturally occurring bacterial communities, mutator bacteria with increased mutation rates emerge at a much higher frequency than expected. From an ecological perspective, this ensures that advantageous mutations facilitate bacterial adaptation to new and/or changing environments at a faster pace. However, at the same time these mutator bacteria are a major cause of severe, antibiotic-resistant nosocomial infections.

Most studies ignore the fact that in natural environments individual organisms live in communities, a complex system of inter-species interactions that drives ecological and evolutionary processes. As a result, it is of paramount importance to understand how the presence of natural competitors affects the elevated mutation rates.

To address this, the EU-funded EMBCC (Evolution of mutator bacteria in a community context) project aimed to investigate the role of the natural microbial community in the selection of mutation rates. For this purpose, the consortium focused on the human-pathogenic bacterium, Pseudomonas aeruginosa, and its behaviour under two different environments, namely the soil and cystic fibrosis (CF).

Researchers initially performed competition experiments in soil microcosms to discover that regardless of the complexity of the microbial community, soil was a hostile environment for selecting high mutation rates. In a model of artificial CF communities, selection and fixation of P. aeruginosa mutators was constrained by the presence of the microbial community. This indicated that the microbial community reduced the availability of beneficial mutations. In chronic CF patients, analysis of P. aeruginosa mutation frequency alongside microbial community diversity indicated that the frequency of mutators correlated with P.aeruginosa prevalence.

Overall, the results of the study underscore for the first time the importance of ongoing biological interactions in microbial communities for the emergence of mutator bacteria. This knowledge bridges the gap between microbial ecology and clinical microbiology and has broad ecological and medical consequences.

Related information


Microbial community, mutator bacteria, Pseudomonas aeruginosa, cystic fibrosis
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