RmpA Regulation of Capsular Polysaccharide Biosynthesis inKlebsiella pneumoniaeCG43

Abstract

Sequence analysis of the large virulence plasmid pLVPK in Klebsiella pneumoniae CG43 revealed the presence of another mucoid factor encoding gene rmpA besides rmpA2. Promoter activity measurement indicated that the deletion of rmpA reduced K2 capsular polysaccharide (CPS) biosynthesis, resulting in decreased colony mucoidy and virulence in mice. Introduction of a multicopy plasmid carrying rmpA restored CPS production in the rmpA or rmpA2 mutant but not in the rcsB mutant. Transformation of the rmpA deletion mutant with an rcsB-carrying plasmid also failed to enhance CPS production, suggesting that a cooperation of RmpA with RcsB is required for regulatory activity. This was further corroborated by the demonstration of in vivo interaction between RmpA and RcsB using two-hybrid analysis and coimmunoprecipitation analysis. A putative Fur binding box was only found at the 5 noncoding region of rmpA. The promoter activity analysis indicated that the deletion of fur increased the rmpA promoter activity. Using electrophoretic mobility shift assay, we further demonstrated that Fur exerts its regulatory activity by binding directly to the promoter. As a result, the fur deletion mutant exhibited an increase in colony mucoidy, CPS production, and virulence in mice. In summary, our results suggested that RmpA activates CPS biosynthesis in K. pneumoniae CG43 via an RcsB-dependent manner. The expression of rmpA is regulated by the availability of iron and is negatively controlled by Fur.

Molecular Typing and Virulence Analysis of Serotype K1 Klebsiella pneumoniae Strains Isolated from Liver Abscess Patients and Stool Samples from Noninfectious Subjects in Hong Kong, Singapore, and Taiwan

“…Since all K1 isolates in this study carried rmpA, we are unable to assess the contribution of this gene in virulence. A previous study confirmed that rmpA is a regulator of capsule formation (3). Loss of this regulator will downregulate capsule synthesis, leading to the loss of phagocytic resistance and the mucoid phenotype.…”

Genomic analysis of diversity, population structure, virulence, and antimicrobial resistance in Klebsiella pneumoniae , an urgent threat to public health

“…Several genetic loci have been identified as virulence factors in K. pneumoniae on the basis of murine models of infection. These include gene clusters associated with the synthesis of siderophore systems yersiniabactin, aerobactin, colibactin, salmochelin (40)(41)(42)(43), or microcin (44); the "regulators of mucoid phenotype" rmpA and rmpA2, which can up-regulate capsule production (45,46); an allantoinase gene cluster (47); the ferric uptake operon kfuABC (48); and the two-component regulator kvgAS (49). Most of these genes were detected only in KpI, except for kfuABC (found in all KpII-B, 75% of KpIII, and 20% of KpI) and allantoinase (found in 50% of KpII-B and 5% of KpI).…”

Regulation of bacterial virulence gene expression by cell envelope stress responses

“…3). 120 This is analogous to the RscAB heterodimers described in E. coli. Indeed, RmpA2 binds to the cps control region, which contains an RcsAB box, and it is hypothesized that this interaction might be enhanced for an RmpA2-RcsB complex.…”

“…The presence of these rmpA genes has been correlated with the HMV phenotype in K. pneumoniae isolates, and RmpA and RmpA2 regulate capsule production in strain CG43. [120][121][122] Furthermore, RmpA or RmpA2, in addition to RcsA, can interact with RcsB and are thought to work in concert with RcsB as accessory proteins to regulate the capsular biosynthesis genes (cps; Fig. 3).…”