Adaptation of Pseudomonas aeruginosa to cultivation in standard laboratory conditions

We studied adaptation of the metabolically versatile bacterium Pseudomonas aeruginosa to standard laboratory conditions by propagating mismatch repair-deficient P. aeruginosa in exponential phase for 24 days in rich medium. In the selective environment of this large-bottleneck mutation accumulation experiment, the bacteria developed shorter lag phases, higher growth rates and higher maximum cell densities. Transcriptional profiling and phenotyping for growth in different media revealed that higher fitness under laboratory conditions evolved via different pathways. Although common adaptive mutations or mutations that define trade-offs were not identified, there was a convergent evolution of transcriptional profiles associated with a shift from biofilm-associated to planktonic lifestyles. Our results indicate that under constant planktonic conditions P. aeruginosa uses several genetic pathways in order to fine-tune adaptation towards faster growth. The selected mutations in the different genetic pathways show a great variety of biofilm, virulence and motility phenotypic trade-offs, thus implying that on the population level, the adaptation of P. aeruginosa to constant conditions does not compromise its versatility.