The Putative Hydrolase YycJ (WalJ) Affects the Coordination of Cell Division with DNA Replication inBacillus subtilisand May Play a Conserved Role in Cell Wall Metabolism

Abstract

Bacteria must accurately replicate and segregate their genetic information to ensure the production of viable daughter cells. The high fidelity of chromosome partitioning is achieved through mechanisms that coordinate cell division with DNA replication. We report that YycJ (WalJ), a predicted member of the metallo-␤-lactamase superfamily found in most low-G؉C Gram-positive bacteria, contributes to the fidelity of cell division in Bacillus subtilis. B. subtilis ⌬walJ (⌬walJ Bsu ) mutants divide over unsegregated chromosomes more frequently than wild-type cells, and this phenotype is exacerbated when DNA replication is inhibited. Two lines of evidence suggest that WalJ Bsu and its ortholog in the Gram-positive pathogen Streptococcus pneumoniae, WalJ Spn (VicX), play a role in cell wall metabolism: (i) strains of B. subtilis and S. pneumoniae lacking walJ exhibit increased sensitivity to a narrow spectrum of cephalosporin antibiotics, and (ii) reducing the expression of a twocomponent system that regulates genes involved in cell wall metabolism, WalRK (YycFG), renders walJ essential for growth in B. subtilis, as observed previously with S. pneumoniae. Together, these results suggest that the enzymatic activity of WalJ directly or indirectly affects cell wall metabolism and is required for accurate coordination of cell division with DNA replication.All cells are faced with the fundamental challenge of duplicating their genetic information and accurately partitioning a complete copy into each new daughter cell. To ensure that the chromosome is stably transmitted with every cell division, all stages of the cell cycle-including DNA replication, cell growth, and cell division-must be carefully coordinated. Bacteria maintain the fidelity of cell division through the combined activity of multiple regulatory pathways. For example, a number of mechanisms function to ensure proper localization of the cytokinetic Z-ring and control the assembly and activity of the division machinery at the septum (1,3,24,29,46). During the late stages of cell division in Bacillus subtilis, a DNA translocase (SftA) helps ensure that chromosomes are fully segregated into daughter cells before septation is completed (8, 36). Failure to properly coordinate the stages of the cell cycle can lead to aberrant division events where the septum forms over the chromosome and results in at least one daughter cell lacking a complete copy of the genome. B. subtilis can recover from these "nucleoid bisection" events through the activity of SpoIIIE, a membrane-bound DNA translocase (64). Although many bacterial cell cycle regulators have been described, our understanding of how the cell cycle is coordinated remains incomplete.Central to the process of cell growth and division is the formation and assembly of new cell wall material along the length of the cell and at the division septum. The Grampositive cell wall is a dynamic structure made of a thick (ϳ50-nm) layer of cross-linked peptidoglycan (murein) cables that wrap around the cell membrane (33). B. subt...

Mismatch repair in Gram-positive bacteria

“…Biochemical studies of WalJ show that it is a Mn 2+ dependent 5-3 exonuclease [32] (Figure 2D). Interestingly, deletion of walJ also causes sensitivity to beta lactam antibiotics, suggesting a role for WalJ in cell wall homeostasis, as the name suggests [69]. Further analysis of walJ will be required to understand the role of this protein in MMR and in cell wall related functions in Grampositive bacteria.…”

Involvement of WalK (VicK) phosphatase activity in setting WalR (VicR) response regulator phosphorylation level and limiting cross‐talk in Streptococcus pneumoniaeD39 cells

“…In addition, both classes of WalRK TCS involve an auxiliary protein, called WalJ (YycJ), which is a predicted member of the metallo-b-lactamase superfamily Winkler and Hoch, 2008;Turck and Bierbaum, 2012). Although its enzymatic function is unknown, accumulated data suggest links among WalJ, WalRK TCS function and peptidoglycan metabolism that, if perturbed, disrupt accurate co-ordination of cell division and DNA replication (Ng et al, 2003;Biller et al, 2011).…”

PePPER: a webserver for prediction of prokaryote promoter elements and regulons

“…These genes represent the WalR regulon [61-64]. This signal transduction pathway is crucial for the regulation of cell wall metabolism and is one the few TCS known to be a virulence factor in S. pneumoniae [61].…”