Transcriptome of Proteus mirabilis in the Murine Urinary Tract: Virulence and Nitrogen Assimilation Gene Expression

Abstract

The enteric bacterium Proteus mirabilis is a common cause of complicated urinary tract infections. In this study, microarrays were used to analyze P. mirabilis gene expression in vivo from experimentally infected mice. Urine was collected at 1, 3, and 7 days postinfection, and RNA was isolated from bacteria in the urine for transcriptional analysis. Across nine microarrays, 471 genes were upregulated and 82 were downregulated in vivo compared to in vitro broth culture. Genes upregulated in vivo encoded mannose-resistant Proteus-like (MR/P) fimbriae, urease, iron uptake systems, amino acid and peptide transporters, pyruvate metabolism enzymes, and a portion of the tricarboxylic acid (TCA) cycle enzymes. Flagella were downregulated. Ammonia assimilation gene glnA (glutamine synthetase) was repressed in vivo, while gdhA (glutamate dehydrogenase) was upregulated in vivo. Contrary to our expectations, ammonia availability due to urease activity in P. mirabilis did not drive this gene expression. A gdhA mutant was growth deficient in minimal medium with citrate as the sole carbon source, and loss of gdhA resulted in a significant fitness defect in the mouse model of urinary tract infection. Unlike Escherichia coli, which represses gdhA and upregulates glnA in vivo and cannot utilize citrate, the data suggest that P. mirabilis uses glutamate dehydrogenase to monitor carbon-nitrogen balance, and this ability contributes to the pathogenic potential of P. mirabilis in the urinary tract.

Initiation of Swarming Motility by Proteus mirabilis Occurs in Response to Specific Cues Present in Urine and Requires Excess L-Glutamine

“…Furthermore, mutation of gdhA results in a fitness defect in the bladder, kidneys, and spleen (53). While the fitness of a glnA mutant has yet to be assessed in the mouse model of infection, in vivo transcriptome data suggest that glutamine synthetase may not contribute significantly to infection.…”

“…During infection of the murine urinary tract, P. mirabilis increases expression levels of gdhA and decreases expression levels of glnA (53), suggesting an inverse requirement for these enzymes during infection and swarming. Furthermore, mutation of gdhA results in a fitness defect in the bladder, kidneys, and spleen (53).…”

Bitter triggers acetylcholine release from polymodal urethral chemosensory cells and bladder reflexes

“…In biofilms, such substances from the Gram-negative bacterium Pseudomonas aeruginosa, one of the predominant causative microorganisms in catheter-associated urinary tract infection (39), can reach concentrations as high as 600 μM (40). On the other hand, glutamate metabolism is positively linked to the pathogenic potential of Proteus mirabilis in the urinary tract (41), and free amino acids (i.e., umami) facilitate bacterial growth in urine (42). Thus, the bitter/umami polymodality of chemosensory cells may serve to broaden the spectrum for recognition of potential hazardous material in the urethral lumen.…”

Cyclopropane-1,2-dicarboxylic acids as new tools for the biophysical investigation ofO-acetylserine sulfhydrylases by fluorimetric methods and saturation transfer difference (STD) NMR

“…Indeed, it has been demonstrated that deletion of genes belonging to the cysteine biosynthetic pathway leads to a bacterial phenotype with reduced virulence, compromised fitness and a susceptibility to antibiotics several fold higher than the wild strains 8,9 . The recent disclosure of a number of additional moonlighting activities of OASS, specifically for OASS-A isoform, that is, toxin activation in some strains of Escherichia coli (E. coli) 10 , gene expression in Bacillus subtilis (B. subtilis) 11 , and the involvement of the enzyme in some pathologically relevant processes as the formation of biofilm and swarming motility, has further focused the interest of researchers toward these proteins [11][12][13][14][15][16][17][18] . These activities span from toxin activation in contact-dependent growth inhibition of uropathogenic E. coli strains 10 , to gene expression in B. subtilis 11 and the involvement of the enzyme in some pathologically-relevant processes as the formation of biofilm and swarming motility 19 .…”