A cell wall damage response mediated by a sensor kinase/response regulator pair enables beta-lactam tolerance

Abstract

The bacterial cell wall is critical for maintenance of cell shape and survival. Following exposure to antibiotics that target enzymes required for cell wall synthesis, bacteria typically lyse. Although several cell envelope stress response systems have been well described, there is little knowledge of systems that modulate cell wall synthesis in response to cell wall damage, particularly in Gram-negative bacteria. Here we describe WigK/WigR, a histidine kinase/response regulator pair that enables Vibrio cholerae, the cholera pathogen, to survive exposure to antibiotics targeting cell wall synthesis in vitro and during infection. Unlike wild-type V. cholerae, mutants lacking wigR fail to recover following exposure to cell-wall–acting antibiotics, and they exhibit a drastically increased cell diameter in the absence of such antibiotics. Conversely, overexpression of wigR leads to cell slimming. Overexpression of activated WigR also results in increased expression of the full set of cell wall synthesis genes and to elevated cell wall content. WigKR-dependent expression of cell wall synthesis genes is induced by various cell-wall–acting antibiotics as well as by overexpression of an endogenous cell wall hydrolase. Thus, WigKR appears to monitor cell wall integrity and to enhance the capacity for increased cell wall production in response to damage. Taken together, these findings implicate WigKR as a regulator of cell wall synthesis that controls cell wall homeostasis in response to antibiotics and likely during normal growth as well.

The Two-Component Signal Transduction System VxrAB Positively Regulates Vibrio cholerae Biofilm Formation

“…Our results demonstrated that deletion of vxrB did not impact motility but that overexpression of VxrB led to a decrease in motility. This is consistent with results from a previous study that demonstrated that overexpression of wild-type VxrB or constitutively active VxrB resulted in a loss of motility (36).…”

“…Another recent study additionally showed that the VxrAB TCS plays a role in cell wall homeostasis in response to antibiotic treatment (in that study, the authors renamed VxrAB as WigKR) (36). However, this is the first report of its role in the regulation of biofilm-gene expression.…”

“…A recent study indicated that the VxrAB system may sense signals generated in response to ␤-lactam exposure, potentially either directly sensing the antibiotics themselves or sensing cell wall stress or degradation products (36). A VxrA homolog in Vibrio parahaemolyticus, VbrK, was shown to directly bind ␤-lactams to activate its cognate RR and stimulate the expression of a ␤-lactamase and additional ␤-lactam antibiotic resistance genes (56).…”

Lytic transglycosylases RlpA and MltC assist in Vibrio cholerae daughter cell separation

“…Overexpression of V. cholerae ’s primary housekeeping endopeptidases, ShyA or ShyC (Dörr et al , ), was unable to appreciably reduce chaining in the ∆2 LTG mutant (Fig. A) (functional expression of these constructs was validated by their ability to complement a mutant defective in multiple endopeptidases [Dörr et al , ]). Similarly, overexpression of V. cholerae ’s only amidase, AmiB (co‐overexpressed with its activators NlpD and EnvC [Uehara et al , ; Yang et al , ; Möll et al , ]), demonstrated functionality by complementing the ∆ amiB mutant (Fig.…”

“…pAM299 was conjugated into V. cholerae as a single crossover, without counterselection. For fluorescent localization or detection of proteins by western blot, genes were cloned into pBAD33 (Guzman et al , ) or pHL100 (Dörr, Alvarez, et al , ).…”