Achromobacter xylosoxidansmodulatesPseudomonas aeruginosavirulence through a multi-target mechanism of competition

The colonization and persistence ofPseudomonas aeruginosain chronically diseased lungs are driven by the production of various virulence factors. However, pulmonary infections in cystic fibrosis (CF) patients are predominantly polymicrobial. WhileAchromobacter xylosoxidansis an opportunistic pathogen in these patients, its impact onP. aeruginosavirulence during co-infection remains largely unknown. This study investigated the interaction betweenP. aeruginosaand two clonally relatedA. xylosoxidansstrains, Ax 198 and Ax 200, co-isolated from a CF patient sputum. We found that the interaction betweenP. aeruginosaand co-isolatedA. xylosoxidanswas strain-dependent, with the Ax 200 strain significantly reducingP. aeruginosavirulence in a zebrafish model, providing the firstin vivoevidence of interaction between these two species during co-infection. Proteomic analysis revealed that theP. aeruginosaproteome was differently impacted by the twoA. xylosoxidansstrains, with Ax 200 altering proteins involved in biofilm formation, swimming motility, iron acquisition, and secretion systems. These proteomic findings were further validated by phenotypic assays, which confirmed thatA. xylosoxidansaffected majorP. aeruginosavirulence phenotypes, including biofilm formation, swimming motility, and siderophore production. Genetic analysis also confirmed that distinct regulatory mechanisms, including mechanisms involved in the iron cycle, may account for the strain-dependent interaction effects ofA. xylosoxidanswithP. aeruginosa. These findings reveal a novel multi-target competitive mechanism through whichA. xylosoxidanssignificantly disruptsP. aeruginosavirulence.