Regulatory roles of an sRNA derived from the 5´ UTR and sequence internal to A in PAO1.

UNLABELLED

Several key virulence factors of are regulated by quorum-sensing systems, small noncoding RNAs (sRNAs), and environmental stress, leading to a high mortality rate. Our previous studies indicated that the alkaline phosphatase LapA regulated PAO1 biofilm formation in a chronic wound model established with porcine skin explants. Notably, one particular sRNA located upstream of the gene was highly expressed in the model. Therefore, the sRNA was further characterized via northern blotting and rapid amplification of cDNA ends. The results revealed that the sRNA we named LapS is 197 nucleotides in length and is derived from the 5´ UTR and sequence internal to the gene. Next, LapS mutation, overexpression, and complementation strains were constructed from the PAO1 strain, and phenotypic experiments associated with were performed and compared with those of the Δ and wild-type strains. The results indicated that LapS is involved in regulating swarming motility, rhamnolipid and alkaline phosphatase production, quorum-sensing systems, and biofilm formation by controlling the level of mRNA under phosphate-depleted conditions. Therefore, this LapS- signaling cascade is beneficial for balancing the virulence regulation of . Additionally, an study indicated that LapS directly and post-transcriptionally regulated at least one unlinked gene, , which encodes bifunctional proline dehydrogenase, a virulence factor of . Collectively, our findings reveal a previously unstudied regulatory sRNA and advance the understanding of the roles of sRNAs in the pathogenicity of .

IMPORTANCE

is a common nosocomial pathogen that contains hundreds of virulence factors regulated by quorum-sensing systems and environmental stress. Small noncoding RNAs (sRNAs) involved in virulence regulation have been identified in . Recently, several potential sRNAs were identified in using transcriptome sequencing. However, some of these novel sRNAs have been functionally characterized. In this study, a previously uncharacterized sRNA, LapS, in PAO1 was identified as a novel sRNA. LapS is involved in regulating swarming motility, rhamnolipid production, and alkaline phosphatase production during phosphate-depleted stress by controlling the level of mRNA. Furthermore, LapS deletion also reduced the mortality rate of in a fast-kill assay. Additionally, LapS directly suppressed PutA, a virulence factor of . This study highlights the role of LapS in modulating virulence during phosphate-depleted stress.