Interactions between metabolism and growth can determine the co-existence ofStaphylococcus aureusandPseudomonas aeruginosa

Most bacteria exist and interact within polymicrobial communities. These interactions produce unique compounds, increased virulence and augmented antibiotic resistance. One community associated with negative healthcare outcomes consists ofPseudomonas aeruginosaandStaphylococcus aureus. When co-cultured, virulence factors secreted byP. aeruginosareduce metabolism and growth inS. aureus. When grownin vitrothis allowsP. aeruginosato driveS. aureustowards extinction. However, when foundin vivo, both species can co-exist. Previous work has noted that this may due to altered gene expression or mutations. However, little is known about how the growth environment could influence co-existence of both species. Using a combination of mathematical modeling and experimentation, we show that changes to bacterial growth and metabolism caused by differences in the growth environment can determine final population composition. We found that changing the carbon source in growth medium affects the ratio of ATP to growth rate for both species, a metric we call absolute growth. We found that as a growth environment increases absolute growth for one species, that species will dominate the co-culture. This is due to interactions between growth, metabolism and metabolism altering virulence factors produced byP. aeruginosa. Finally, we show that the relationship between absolute growth and final population composition can be perturbed by altering the spatial structure in the community. Our results demonstrate that differences in growth environment can account for conflicting observations regarding the co-existence of these bacterial species in the literature, and may offer a novel mechanism to manipulate polymicrobial populations.