The Small RNA RyhB Contributes to Siderophore Production and Virulence of Uropathogenic Escherichia coli

Abstract

eIn Escherichia coli, the small regulatory noncoding RNA (sRNA) RyhB and the global ferric uptake regulator (Fur) mediate iron acquisition and storage control. Iron is both essential and potentially toxic for most living organisms, making the precise maintenance of iron homeostasis necessary for survival. While the roles of these regulators in iron homeostasis have been well studied in a nonpathogenic E. coli strain, their impact on the production of virulence-associated factors is still unknown for a pathogenic E. coli strain. We thus investigated the roles of RyhB and Fur in iron homeostasis and virulence of the uropathogenic E. coli (UPEC) strain CFT073. In a murine model of urinary tract infection (UTI), deletion of fur alone did not attenuate virulence, whereas a ⌬ryhB mutant and a ⌬fur ⌬ryhB double mutant showed significantly reduced bladder colonization. The ⌬fur mutant was more sensitive to oxidative stress and produced more of the siderophores enterobactin, salmochelins, and aerobactin than the wild-type strain. In contrast, while RyhB was not implicated in oxidative stress resistance, the ⌬ryhB mutant produced lower levels of siderophores. This decrease was correlated with the downregulation of shiA (encoding a transporter of shikimate, a precursor of enterobactin and salmochelin biosynthesis) and iucD (involved in aerobactin biosynthesis) in this mutant grown in minimal medium or in human urine. iucD was also downregulated in bladders infected with the ⌬ryhB mutant compared to those infected with the wild-type strain. Our results thus demonstrate that the sRNA RyhB is involved in production of iron acquisition systems and colonization of the urinary tract by pathogenic E. coli.

The prrF -Encoded Small Regulatory RNAs Are Required for Iron Homeostasis and Virulence of Pseudomonas aeruginosa

“…Combined with a previous study demonstrating the role of the PrrF sRNAs in production of the PQS quorum sensing molecule (33), these results demonstrate the central role of the prrF locus in the physiology and pathogenesis of P. aeruginosa. A recent report demonstrated that a mutant for the iron-regulated RyhB sRNA of uropathogenic E. coli (UPEC) was defective for bladder colonization in a murine model of urinary tract infection (68). Notably, the ryhB mutant of E. coli was also shown in this study to be defective for siderophore production, a known contributor to UPEC virulence (69).…”

“…Asterisks indicate the following P values as determined by two-tailed Student's t test when comparing values upon heme or iron supplementation to that of the low-iron sample: *, P Ͻ 0.05; **, P Ͻ 0.001; ***, P Ͻ 0.0001; ****, P Ͻ 0.00001. nonpathogenic E. coli (70), the UPEC ⌬ryhB mutant displayed decreased expression of shiA, encoding a permease for shikimate, a required substrate of enterobactin biosynthesis. Moreover, this study also showed that genes encoding biosynthetic enzymes for the hydroxamate siderophore aerobactin were downregulated in the ⌬ryhB mutant (68). Thus, the RyhB sRNA of UPEC contributes to siderophore production by multiple mechanisms, likely promoting colonization and survival during urinary tract infection.…”

Fur Represses Adhesion to, Invasion of, and Intracellular Bacterial Community Formation within Bladder Epithelial Cells and Motility in Uropathogenic Escherichia coli

“…Unlike the case with the fur mutant, the deletion of ryhB increased the expression of flagellar genes but not fimbrial genes. In contrast, the ryhB mutant formed a lower number of colonies than the wild type in the bladders of mice (30). RyhB represses the expression of nonessential iron-using metabolic enzymes under low-iron conditions and then increases the availability of iron for essential iron-using metabolic enzymes (28).…”

“…An in vivo study of UPEC using a mouse model showed that the deletion of fur did not attenuate UPEC virulence during UTIs because the fur mutant formed a number of colonies in the bladder similar to that of the wild-type strain (30). Both in vivo and in vitro studies using clinical and laboratory UPEC strains showed that siderophore production is necessary for virulence (31,32).…”

Iron Homeostasis Regulates the Genotoxicity of Escherichia coli That Produces Colibactin

“…RyhB is a small RNA that recruits RNase E and facilitates the degradation of mRNA targets (27,28). Whereas only a few studies have demonstrated the impact of RyhB on virulence in pathogenic E. coli, for instance, through siderophore production (29), several studies have demonstrated that this sRNA is implicated in the virulence-associated processes of other pathogenic bacteria, such as Shigella flexneri (2) or Shigella dysenteriae (30). This study provides new evidence that RyhB is involved in the production of a virulence factor in pathogenic E. coli through the regulation of clbA transcription, which leads to the modulation of colibactin production.…”