RNAseq reveals thatPseudomonas aeruginosamounts medium-dependent competitive responses when sensing diffusible cues fromBurkholderia cenocepacia

AbstractMost habitats on earth are colonized by diverse bacterial communities, offering ample opportunities for inter-species interactions. While competition for space and nutrients might often dominate such interactions, little is known about whether bacteria can sense competitors and mount specific responses to withstand their attacks. The competition-sensing hypothesis proposes that bacteria can do so through nutrient stress and cell damage cues. Here, we conducted a replicated RNAseq-transcriptomic study to test this hypothesis. We exposedPseudomonas aeruginosato either its own spent medium or to the supernatant of its competitorBurkholderia cenocepacia. Compared to controls, we detected significant changes in the transcriptome ofP. aeruginosathat entail both general responses to spent medium and specific responses to the competitor. Specifically, genes encoding various competitive traits, including the type-VI secretion system, the siderophore pyoverdine, and the toxins phenazines and hydrogen cyanide, were upregulated when exposed to the competitor supernatant. Similarly, several genes coding for stress response and quorum-sensing regulators were overexpressed. Moreover, we found transcriptional responses to vary as a function of iron availability, whereby metabolically more costly responses were launched under iron rich conditions. Altogether, our results reveal nuanced competitive responses ofP. aeruginosawhen exposed toB. cenocepaciasupernatant, integrating both environmental and social cues.