Arms-race and fluctuating-selection dynamics in Pseudomonas aeruginosa bacteria coevolving with phage OMKO1

Experimental evolution studies have examined coevolutionary dynamics between bacteria and lytic phages, where two models for antagonistic coevolution dominate: arms-race dynamics (ARD) and fluctuating-selection dynamics (FSD). Here, we tested the ability for Pseudomonas aeruginosa to coevolve with phage OMKO1 during 10 passages in the laboratory; whether ARD versus FSD coevolution occurred; and how coevolution affected a predicted phenotypic trade-off between phage resistance and antibiotic sensitivity. We used a unique “deep” sampling design, where 96 bacterial clones per passage were obtained from the three replicate coevolving communities. Next, we examined phenotypic changes in growth ability, susceptibility to phage attack, and resistance against antibiotics. Results confirmed that the bacteria and phages coexisted throughout the study with one community undergoing ARD while the other two showed evidence for FSD. Surprisingly, only the ARD bacteria demonstrated the anticipated trad...