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The lytE gene of Bacillus subtilis 168 encodes a cell wall hydrolase.

ABSTRACT: Bacillus subtilis cell wall-bound protein CWBP33 is encoded by lytE, a gene expressed during the exponential growth phase. Sequence analysis of LytE, a 33-kDa protein, reveals two domains. The N-terminal domain contains a threefold-repeated motif common to several peptidoglycan binding proteins, while the C-terminal domain, probably carrying the catalytic activity, has homology with certain exoproteins. Zymographs unambiguously reveal that the absence of CWBP33, due to inactivation of lytE, is accompanied by the loss of a lytic activity. In lytE mutants, the cell autolysis rate is significantly decreased, although autolysis of corresponding, purified cell walls does not seem to be affected.

SUBMITTER: Margot P

PROVIDER: S-EPMC106949 | biostudies-literature | 1998 Feb

REPOSITORIES: biostudies-literature

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The lytE gene of Bacillus subtilis 168 encodes a cell wall hydrolase.

Margot P P Wahlen M M Gholamhoseinian A A Piggot P P Karamata D D

Journal of bacteriology 19980201 3

Bacillus subtilis cell wall-bound protein CWBP33 is encoded by lytE, a gene expressed during the exponential growth phase. Sequence analysis of LytE, a 33-kDa protein, reveals two domains. The N-terminal domain contains a threefold-repeated motif common to several peptidoglycan binding proteins, while the C-terminal domain, probably carrying the catalytic activity, has homology with certain exoproteins. Zymographs unambiguously reveal that the absence of CWBP33, due to inactivation of lytE, is a ...[more]

PMID: 9457885

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Project description:UnlabelledIn Bacillus subtilis, the dl-endopeptidase LytE is responsible for lateral peptidoglycan hydrolysis during cell elongation. We found that σ(I)-dependent transcription of lytE is considerably enhanced in a strain with a mutation in ltaS, which encodes a major lipoteichoic acid (LTA) synthase. Similar enhancements were observed in mutants that affect the glycolipid anchor and wall teichoic acid (WTA) synthetic pathways. Immunofluorescence microscopy revealed that the LytE foci were considerably increased in these mutants. The localization patterns of LytE on the sidewalls appeared to be helix-like in LTA-defective or WTA-reduced cells and evenly distributed on WTA-depleted or -defective cell surfaces. These results strongly suggested that LTA and WTA affect both σ(I)-dependent expression and localization of LytE. Interestingly, increased LytE localization along the sidewall in the ltaS mutant largely occurred in an MreBH-independent manner. Moreover, we found that cell surface decorations with LTA and WTA are gradually reduced at increased culture temperatures and that LTA rather than WTA on the cell surface is reduced at high temperatures. In contrast, the amount of LytE on the cell surface gradually increased under heat stress conditions. Taken together, these results indicated that reductions in these anionic polymers at high temperatures might give rise to increases in SigI-dependent expression and cell surface localization of LytE at high temperatures.ImportanceThe bacterial cell wall is required for maintaining cell shape and bearing environmental stresses. The Gram-positive cell wall consists of mesh-like peptidoglycan and covalently linked wall teichoic acid and lipoteichoic acid polymers. It is important to determine if these anionic polymers are required for proliferation and environmental adaptation. Here, we demonstrated that these polymers affect the expression and localization of a peptidoglycan hydrolase LytE required for lateral cell wall elongation. Moreover, we found that cell surface decorations with teichoic acid polymers are substantially decreased at high temperatures and that the peptidoglycan hydrolase is consequently increased. These findings suggest that teichoic acid polymers control lateral peptidoglycan hydrolysis by LytE, and bacteria drastically change their cell wall content to adapt to their environment.

Project description:Most bacteria are surrounded by their cell wall, containing a highly cross-linked protective envelope of peptidoglycan. To grow, bacteria must continuously remodel their wall, inserting new material and breaking old bonds. Bond cleavage is performed by cell wall hydrolases, allowing the wall to expand. Understanding the functions of individual hydrolases has been impeded by their redundancy: single knockouts usually present no phenotype. We used an exhaustive multiple-knockout approach to determine the minimal set of hydrolases required for growth in Bacillus subtilis. We identified 42 candidate hydrolases. Strikingly, we were able to remove all but two of these genes in a single strain; this "∆40" strain shows only a mild reduction in growth rate, indicating that none of the 40 hydrolases are necessary for growth. The ∆40 strain does not detectably shed old wall, suggesting that turnover is not essential for growth. The remaining hydrolases in the ∆40 strain are LytE and CwlO, previously shown to be synthetically lethal. Either can be removed in ∆40, indicating that either hydrolase alone is sufficient for cell growth. Screening of environmental conditions and biochemistry revealed that LytE activity is inhibited by Mg2+ and that RlpA-like proteins may stimulate LytE activity. Together, these results suggest that the only essential function of cell wall hydrolases in B. subtilis is to enable cell growth by expanding the wall and that LytE or CwlO alone are sufficient for this function. These experiments introduce the ∆40 strain as a tool to study hydrolase activity and regulation in B. subtilis.IMPORTANCEIn order to grow, bacterial cells must both create and break down their cell wall. The enzymes that are responsible for these processes are the target of some of our best antibiotics. Our understanding of the proteins that break down the wall- cell wall hydrolases-has been limited by redundancy among the large number of hydrolases many bacteria contain. To solve this problem, we identified 42 cell wall hydrolases in Bacillus subtilis and created a strain lacking 40 of them. We show that cells can survive using only a single cell wall hydrolase; this means that to understand the growth of B. subtilis in standard laboratory conditions, it is only necessary to study a very limited number of proteins, simplifying the problem substantially. We additionally show that the ∆40 strain is a research tool to characterize hydrolases, using it to identify three "helper" hydrolases that act in certain stress conditions.

Dataset Information

The lytE gene of Bacillus subtilis 168 encodes a cell wall hydrolase.

Publications

The lytE gene of Bacillus subtilis 168 encodes a cell wall hydrolase.

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