Type IV PilD mutant stimulates the formation of persister cells in Pseudomonas aeruginosa

Pseudomonas aeruginosa clinical isolates that lack motility do not express type IV pilin, yet the biological roles of this absence in the infection process remain poorly understood. We asked whether the absence of motility in these bacteria is associated with increased antibiotic persistence. In this study, we analysed type IV PilD protein sequences in the database and conducted antibiotic-tolerant persister cell assays. We found that PilD variants were common in P. aeruginosa clinical isolates. Our results revealed that inactivation of PilD resulted in a significantly higher level of surviving persister cells following ciprofloxacin treatment. This PilD-mediated persistence did not involve previously described mechanisms, such as phenazine pyocyanin, biofilm or stringent response. Our findings connect the non-motility of clinical P. aeruginosa isolates with the survival of persister cells, highlighting the clinical significance for the development of strategies to eradicate P. aeruginosa infections.