Evolution of species interactions in a biofilm community

In it together Biofilms are specialized environments where communities of microorganisms are insulated from the outside world by an extracellular polymer matrix that they themselves secrete. The resulting microbial mats have been compared to tropical rainforests in terms of complexity and biodiversity. Selective pressures on such biofilms are likely to demand intense interactions between the individual bacteria, and an experiment with a simple community of two species (soil dwellers Pseudomonas putida and Acinetobacter sp.) shows just how close that relationship is. The physical structure of the community altered, to the mutual benefit of both species, as a result of a simple mutation in the genome of one of the species. In the absence of a partner the mutation (in P. putida) would have been deleterious. This system demonstrates the importance of interspecies interactions, and may be useful in work on the evolution of these interactions.