Polymicrobial interactions between commensal obligate anaerobic bacteria and cystic fibrosis pathogen P. aeruginosa

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ABSTRACT It has become apparent that the human microbiota impacts virtually every facet of human health, including directly influencing clinical outcomes for certain diseases. The mechanisms that mediate these effects are often the polymicrobial interactions between incoming pathogens and commensal microbes. In Cystic Fibrosis (CF), a genetic disease in which patients are often afflicted with chronic bacterial infections, most notably Pseudomonas aeruginosa, the effect of the resident anaerobes in disease outcome is conflicting and poorly studied. However, microbiota-based studies have revealed that specific resident obligate anaerobic respiratory bacteria are associated with improved CF outcomes, and limited evidence suggests that specific obligate anaerobic bacteria impair P. aeruginosa colonization. Indeed, I recently discovered that the obligate anaerobic respiratory bacterial species Porphyromonas catoniae inhibits P. aeruginosa growth by a contact-independent mechanism. Genomic mining of the P. catoniae genome revealed no gene clusters known to be associated with antimicrobial synthesis, we therefore hypothesize that P. catoniae inhibits P. aeruginosa by a novel mechanism. The proposal will take a multifarious approach to investigate P. catoniae inhibition of P. aeruginosa. To this end, a P. catoniae transposon mutant strain library will be constructed and screened to identify the gene(s) responsible for inhibitory activity. Mass spectrometry will be utilized to characterize the P. catoniae “secretome” to identify potential anti-P. aeruginosa compound(s). The P. aeruginosa global transcriptional response to P. catoniae will be examined and measured by RNA-seq. Moreover, P. aeruginosa Tn-seq will be used to illuminate which genes are associated with survival in the presence of P. catoniae. Furthermore, we will assess the effects of bacterial lifestyle (planktonic vs. biofilm), CF relevant environmental stimuli, and the addition of other obligate anaerobic respiratory bacteria on this interaction. Alternations in biofilm biogeography under CF relevant conditions including the presence of other commensals will be assessed with fluorescence confocal microscopy. En masse, this proposal seeks to provide novel insight into interbacterial behavior and lifestyle that ultimately could reveal novel antimicrobials and/or molecular target(s) to treat chronic P. aeruginosa infections and improve the clinical outcomes for CF patients.