Investigation of the small RNA GlmZ in uropathogenic Proteus mirabilis

Proteus mirabilis is a Gram-negative, facultative anaerobic bacterium, it is a part of the normal flora of human intestinal tract, meanwhile, it is also an opportunistic pathogen which causes urinary tract infections (UTIs) and catheter-associated urinary tract infections (CAUTIs). Bacterial small RNAs are a group of small non-coding RNAs ranging from 50 to 500 nucleotides, which are involved in the post-transcriptional control of bacteria gene expression by complementary base-pairing with their target mRNAs. In Escherichia coli, sRNA GlmY and GlmZ have been found to up-regulate the translation of glmS (glucosamine-6-phosphate synthase) mRNA. In P. mirabilis, the two-component system QseE/F have been found to regulate the small RNAs GlmY and GlmZ using reporter assay in our previous study. Small RNA GlmY has been found to regulate the swarming ability of P. mirabilis, while the functioning roles of GlmZ has yet to be found. In this study, we investigated the roles of GlmZ in P. mirabilis. The expression of GlmZ was greatly down-regulated in the qseF mutant. The amount of GlmZ was also significantly reduced under the presence of urea or glucosamine. We constructed a P. mirabilis glmZ mutant and GlmZ was substituted with a kanamycin resistant cassette. In our study, we have found that glmZ mutant has a lower survival rate relative to wild-type under treatment with oxidative stress, glmZ mutant also has a reduced survival rate in macrophages. Futhermore, glmZ-overexpression strain increases the biofilm formation and the survival rate under acidic stress relative to wild-type. To identify potential targets of GlmZ, we used bioinformatic tools to predict possible GlmZ target genes and confirmed the target gene expression with real-time PCR. We have found that the expression of rpoS, murA and glmS are down-regulated in glmZ mutant. Altogether, our study indicates that sRNA GlmZ plays a role in the stress reponse regulation of P. mirabilis through up-regulating the expression of the stress response regulator, RpoS, helping P. mirabilis to survive under oxidative and acidic stress.