Phenotypic variation among Pseudomonas aeruginosa populations when coevolving with phage OMKO1

Experimental evolution studies have long been used to examine coevolutionary dynamics between phage and bacteria; however, here we extend traditional coevolution studies to examine both coevolutionary dynamics of phage OMKO1 and Pseudomonas aeruginosa and the evolution of an anticipated trade-off between phage resistance and antibiotic resistance. Lytic phage OMKO1and P. aeruginosa are able to coexist over a 10-day evolution experiment and time shift assays reveal that coevolutionary dynamics of the two microbes follows an arms race pattern of coevolution with slight variations in dynamics between the three experimental populations. Measurements of antibiotic resistance at both a clonal and population level demonstrate that one of the experimental populations, population 1, evolved phage resistance at the cost of resistance to tetracycline and erythromycin. Whole genome sequencing of bacterial populations reveal that experimental populations accrue the more mutations than the control population. In each experimental population, mutations were found in genes involved in biosynthesis of flagella, type IV pilus and lipopolysaccharide; no mutations in these genes were observed in the control population. Population 1 had three mutations in fleQ, wzz1 and wzz2, that rose to fixation in the population at the same passage that the trade-off between phage resistance and antibiotic resistance was observed. Results of this coevolution experiment underscore the complexities involved in predicting and reproducing evolutionary outcomes which suggests the further investigation is needed to inform expectations about phage-bacteria evolutionary interactions.