The Pseudomonas aeruginosa PilSR Two-Component System Regulates Both Twitching and Swimming Motilities

• Published in: mBio 2018-07, Vol.9 (4)
• Main Authors: Kilmury, Sara L N, Burrows, Lori L
• Format: Article
• Language: English
• Subjects: Bacterial Proteins - genetics; cell surface; cystic fibrosis; Down-Regulation; Fimbriae Proteins - genetics; Fimbriae, Bacterial - genetics; Fimbriae, Bacterial - metabolism; Flagella - physiology; flagellar gene regulation; Gene Expression Regulation, Bacterial; Movement; Pseudomonas aeruginosa - genetics; Transcription Factors - genetics; Transcriptional Activation; two-component regulatory systems; type IV pili; Up-Regulation
• ISSN: 2161-2129; 2150-7511
• DOI: 10.1128/mBio.01310-18

Motility is an important virulence trait for many bacterial pathogens, allowing them to position themselves in appropriate locations at appropriate times. The motility structures type IV pili and flagella are also involved in sensing surface contact, which modulates pathogenicity. In , the PilS-PilR two-component system (TCS) regulates expression of the type IV pilus (T4P) major subunit PilA, while biosynthesis of the single polar flagellum is regulated by a hierarchical system that includes the FleSR TCS. Previous studies of and implicated PilR in regulation of non-T4P-related genes, including some involved in flagellar biosynthesis. Here we used transcriptome sequencing (RNA-seq) analysis to identify genes in addition to with changes in expression in the absence of Among the genes identified were 10 genes whose transcription increased in the mutant but decreased in the mutant, despite both mutants lacking T4P and pilus-related phenotypes. The products of these inversely dysregulated genes, many of which were hypothetical, may be important for virulence and surface-associated behaviors, as mutants had altered swarming motility, biofilm formation, type VI secretion system expression, and pathogenicity in a nematode model. Further, the PilSR TCS positively regulated transcription of , and thus many genes in the FleSR regulon. As a result, deletion mutants had defects in swimming motility that were independent of the loss of PilA. Together, these data suggest that in addition to controlling T4P expression, PilSR could have a broader role in the regulation of motility and surface sensing behaviors. Surface appendages such as type IV pili and flagella are important for establishing surface attachment and infection in a host in response to appropriate cues. The PilSR regulatory system that controls type IV pilus expression in has an established role in expression of the major pilin PilA. Here we provide evidence supporting a new role for PilSR in regulating flagellum-dependent swimming motility in addition to pilus-dependent twitching motility. Further, even though both and mutants lack PilA and pili, we identified sets of genes downregulated in the mutant and upregulated in a mutant as well as genes downregulated only in a mutant, independent of pilus expression. This finding suggests that change in the inner membrane levels of PilA is only one of the cues to which PilR responds to modulate gene expression. Identification of PilR as a regulator of multiple mot