RNA-Seq reveals thatPseudomonas aeruginosamounts growth medium-dependent competitive responses when sensing diffusible cues fromBurkholderia cenocepacia

Abstract

Most 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 exposed Pseudomonas aeruginosa to either its own spent medium or to the supernatant of its competitor Burkholderia cenocepacia. Compared to controls, we detected significant changes in the transcriptome of P. aeruginosa that 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 of P. aeruginosa when exposed to B. cenocepacia supernatant, integrating both environmental and social cues.

A green-fluorescent siderophore protects bacterial communities from UV damage

“…We note, however, that the preventive 'sunscreen' protection and the curative protection against ROS formation are non-mutually exclusive and potentially complementary mechanisms that likely come with different costs and benefits depending on prior levels of secreted pyoverdine and the nature of the environmental stress. On a more general level, these dual benefits suggests that the upregulation of pyoverdine might be part of a general stress response, a hypothesis that is also supported by the observation of increased pyoverdine expression after exposure of P. aeruginosa to competitor supernatants (Leinweber et al 2023). This hypothesis requires careful testing by investigating how pyoverdine expression and transport are fine-tuned in response to different environmental stressors.…”