ROLE OF INTERSPECIFIC INTERACTIONS IN THE EVOLUTION OF MUTATOR BACTERIA

LUJÁN AM; MADSEN L; MARVIG R; SHARMA MD; SMANIA AM; KROGH JOHANSEN H; SOREN M; BUCKLING A

Mar del Plata

Congreso; LI Reunión Anual de la Sociedad Argentina de Investigaciones Bioquímicas y Biología Molecular, SAIB; 2015

Mutator bacteria can reach high frequencies in natural bacterial populations and are a major cause of antibioticresistantinfections. The causes and consequences of bacterial elevated mutation rates have been widely studied andresults suggest that mutators might be selected because their higher probability of generating beneficial mutations.However, this evidence is based on pure test-tube studies that have largely ignored a crucial feature of theenvironment: the microbial community (MC). Here, we investigate for the first time the role of the MC in theselection of Pseudomonas aeruginosa mutators in a cystic fibrosis (CF) context. By competing P. aeruginosa nonmutator and mutator strains in artificial CF communities (B. cenopacea, S. aureus and A.baumanii), we observed thatmutator enrichment occurs only in the absence of the MC. Fitness determination of evolved strains suggest that thepresence of the MC reduces the availability of beneficial mutations and might prevent mutator hitchhiking. Also, weconducted a survey to investigate whether there was a link between the MC diversity and P. aeruginosa mutation frequency in natural CF communities. We found a negative correlation between P. aeruginosa mutation frequencyand MC diversity. Our results demonstrate that interspecific interactions occurring in CF microbial communities actas a selective force for P. aeruginosa mutators.