Molecular Characterization of an <i>atl</i> Null Mutant of <i>Staphylococcus aureus</i>

Takahashi, Junko; Komatsuzawa, Hitoshi; Yamada, Sakuo; Nishida, Tetsuya; Labischinski, Harald; Fujiwara, Takanori; Ohara, Masaru; Yamagishi, Jun‐ichi; Sugai, Motoyuki

doi:10.1111/j.1348-0421.2002.tb02741.x

Cited by 80 publications

(76 citation statements)

References 29 publications

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“…In Staphylococcus aureus, the Atl protein is processed to yield two hydrolases, an amidase and glucosaminidase (49), and strains lacking Atl grow as clusters of unseparated cells (50). Mutants lacking the Sle1 N-acetylmuramyl-L-alanine amidase have multiple, misplaced, and sometimes curved septa that are positioned at odd angles so that they do not bisect daughter cells equally, effects that are magnified greatly in an atl sle1 double mutant (29).…”

Section: Discussionmentioning

confidence: 99%

Role of Peptidoglycan Amidases in the Development and Morphology of the Division Septum in Escherichia coli

2007

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Escherichia coli contains multiple peptidoglycan-specific hydrolases, but their physiological purposes are poorly understood. Several mutants lacking combinations of hydrolases grow as chains of unseparated cells, indicating that these enzymes help cleave the septum to separate daughter cells after cell division. Here, we confirm previous observations that in the absence of two or more amidases, thickened and dark bands, which we term septal peptidoglycan (SP) rings, appear at division sites in isolated sacculi. The formation of SP rings depends on active cell division, and they apparently represent a cell division structure that accumulates because septal synthesis and hydrolysis are uncoupled. Even though septal constriction was incomplete, SP rings exhibited two properties of mature cell poles: they behaved as though composed of inert peptidoglycan, and they attracted the IcsA protein. Despite not being separated by a completed peptidoglycan wall, adjacent cells in these chains were often compartmentalized by the inner membrane, indicating that cytokinesis could occur in the absence of invagination of the entire cell envelope. Finally, deletion of penicillin-binding protein 5 from amidase mutants exacerbated the formation of twisted chains, producing numerous cells having septa with abnormal placements and geometries. The results suggest that the amidases are necessary for continued peptidoglycan synthesis during cell division, that their activities help create a septum having the appropriate geometry, and that they may contribute to the development of inert peptidoglycan.Most eubacteria produce multiple hydrolases that cleave different bonds within the peptidoglycan (PG or murein) cell wall: amidases remove peptide side chains from the carbohydrate polymer, endopeptidases cleave cross-linked peptides that connect the glycan chains, and lytic transglycosylases hydrolyze the glycan backbone (24, 47). These PG-specific hydrolases were once thought to be essential for inserting new material into the wall during bacterial growth (24, 25), a view based on the reasonable hypothesis that cross-links between the glycan chains had to be broken so that new PG strands could be incorporated into the existing wall (31). However, bacterial growth continues perfectly well in the absence of these dedicated hydrolases, including almost all of the amidases, endopeptidases, and lytic transglycosylases (14,22,23), meaning that any bond-breaking during normal cell wall elongation must be performed by other enzymes. So why, then, does Escherichia coli carry so many murein-specific hydrolases?In the gram-positive bacteria, PG hydrolases split the septum that separates daughter cells at the end of cell division. For example, in Streptococcus pneumoniae, LytA (an amidase) and LytB (a glucosaminidase) localize to the equatorial and polar regions, respectively, and mutants lacking either hydrolase grow in long chains, with double mutants being especially deficient in cell separation (13,46). In Bacillus subtilis, the DL-endopeptidases ...

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Section: Discussionmentioning

confidence: 99%

Role of Peptidoglycan Amidases in the Development and Morphology of the Division Septum in Escherichia coli

2007

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“…There are multiple examples of mutations in murein hydrolase genes in both gram-positive and gram-negative bacteria that result in the inability of the cells to separate (25,38,51,65,70,71,108,118,244,249). Based on the frequency with which murein hydrolase mutations are associated with this phenotype, the primary functions of these enzymes in daughter cell separation are unambiguous.…”

Section: Murein Hydrolasesmentioning

confidence: 99%

Molecular Control of Bacterial Death and Lysis

Rice

Bayles

2008

Microbiol Mol Biol Rev

320

312

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SUMMARY Although the phenomenon of bacterial cell death and lysis has been studied for over 100 years, the contribution of these important processes to bacterial physiology and development has only recently been recognized. Contemporary study of cell death and lysis in a number of different bacteria has revealed that these processes, once thought of as being passive and unregulated, are actually governed by highly complex regulatory systems. An emerging paradigm in this field suggests that, analogous to programmed cell death in eukaryotes, regulated cell death and lysis in bacteria play an important role in both developmental processes, such as competence and biofilm development, and the elimination of damaged cells, such as those irreversibly injured by environmental or antibiotic stress. Further study in this exciting field of bacterial research may provide new insight into the potential evolutionary link between control of cell death in bacteria and programmed cell death (apoptosis) in eukaryotes.

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“…Earlier work demonstrated that Atl functions as an endo-␤-N-acetylglucosaminidase (12,13). Although initially designated autolysin (Atl), the S. aureus atl mutant does not display an autolysis phenotype yet forms large clusters of incompletely separated bacteria and is defective for penicillin-induced killing (14). The LysM domains of Sle1 promote its binding to cross wall peptidoglycan, and sle1 mutants also form clusters of incompletely separated bacteria (3,7).…”

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confidence: 99%

SagB Glucosaminidase Is a Determinant of Staphylococcus aureus Glycan Chain Length, Antibiotic Susceptibility, and Protein Secretion

et al. 2016

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The envelope of Staphylococcus aureus is comprised of peptidoglycan and its attached secondary polymers, teichoic acid, capsular polysaccharide, and protein. Peptidoglycan synthesis involves polymerization of lipid II precursors into glycan strands that are cross-linked at wall peptides. It is not clear whether peptidoglycan structure is principally determined during polymerization or whether processive enzymes affect cell wall structure and function, for example, by generating conduits for protein secretion. We show here that S. aureus lacking SagB, a membrane-associated N-acetylglucosaminidase, displays growth and cell-morphological defects caused by the exaggerated length of peptidoglycan strands. SagB cleaves polymerized glycan strands to their physiological length and modulates antibiotic resistance in methicillin-resistant S. aureus (MRSA). Deletion of sagB perturbs protein trafficking into and across the envelope, conferring defects in cell wall anchoring and secretion, as well as aberrant excretion of cytoplasmic proteins. IMPORTANCEStaphylococcus aureus is thought to secrete proteins across the plasma membrane via the Sec pathway; however, protein transport across the cell wall envelope has heretofore not been studied. We report that S. aureus sagB mutants generate elongated peptidoglycan strands and display defects in protein secretion as well as aberrant excretion of cytoplasmic proteins. These results suggest that the thick peptidoglycan layer of staphylococci presents a barrier for protein secretion and that SagB appears to extend the Sec pathway across the cell wall envelope. Staphylococcus aureus, a Gram-positive bacterial pathogen, replicates via septal assembly of membranes and peptidoglycan into the cross wall compartment (1, 2). The peptidoglycan of the cross wall is split by murein hydrolases, separating daughter cells that assume a spherical shape (3). Earlier work identified three murein hydrolases with cross-wall-splitting activities: Atl (autolysin), Sle1, and LytN (3-5). Atl and Sle1 are secreted into the extracellular milieu and subsequently cleave septal peptidoglycan at the cross wall but not elsewhere as access is restricted by teichoic acid modification of peptidoglycan (6-8). LytN, on the other hand, is secreted into the cross wall compartment (5). S. aureus Atl is synthesized as a preproenzyme with an N-terminal signal peptide and prodomain (9, 10). Secreted pro-Atl is processed to generate Atl N-acetylmuramoyl-L-Ala-amidase (Atl AM ) and Atl Nacetylglucosaminidase (Atl GL ), and each binds via GW domains to lipoteichoic acids (10-12). Earlier work demonstrated that Atl functions as an endo-␤-N-acetylglucosaminidase (12, 13). Although initially designated autolysin (Atl), the S. aureus atl mutant does not display an autolysis phenotype yet forms large clusters of incompletely separated bacteria and is defective for penicillin-induced killing (14). The LysM domains of Sle1 promote its binding to cross wall peptidoglycan, and sle1 mutants also form clusters of incompletely s...

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Molecular Characterization of an atl Null Mutant of Staphylococcus aureus

Cited by 80 publications

References 29 publications

Role of Peptidoglycan Amidases in the Development and Morphology of the Division Septum in Escherichia coli

Role of Peptidoglycan Amidases in the Development and Morphology of the Division Septum in Escherichia coli

Molecular Control of Bacterial Death and Lysis

SagB Glucosaminidase Is a Determinant of Staphylococcus aureus Glycan Chain Length, Antibiotic Susceptibility, and Protein Secretion

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