Microbial Cell Walls and Membranes

Rogers, H. J.; Perkins, H. R.; Ward, J. B.

doi:10.1007/978-94-011-6014-8

Cited by 366 publications

(151 citation statements)

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“…Order is a feature of all polymers including amorphous ones. Regular structures must surely be crystalline, but there is much evidence to show that peptidoglycan in bacteria is not (12,21). All of the evidence from thread measurements (18,25,26) shows the cell wall to be in no way different from other amorphous polymers.…”

Section: Discussionmentioning

confidence: 99%

Mechanical properties of Bacillus subtilis cell walls: effects of ions and lysozyme

1991

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Bacterial threads of BacUlus subtilis have been immersed in, and redrawn from, water of various pH values, in solutions of (NH4)2SO4 and NaCI of various concentrations, and in Iysozyme solutions. The changes in the tensile strength, elastic modulus, and other mechanical properties of the bacterial cell wall due to these treatments were obtained. The data show that change in pH has little effect but that as the salt concentration is increased, the cell walls become more ductile. A high salt concentration (1 M NaCI) can reduce the modulus by a factor of 26 to 13.5 MPa at 81% relative humidity and the strength by a factor of only 2.5. Despite attacking the septal-wall region of the cellular filaments, Iysozyme has no effect on the mechanical properties. There is no significant change in the stress relaxation behavior due to any of the treatments. The dependence of mechanical properties on the salt concentration is discussed in terms of the polyelectrolyte nature of cell walls. The evidence presented in this and the accompanying paper (J. J. Thwaites and U. C. Surana, J. Bacteriol., 173:197-203, 1991) supports the idea that the peptidoglycan in bacterial cell wall is an entanglement network with a large degree of molecular flexibility, with some order but no regular structure.

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Section: Discussionmentioning

confidence: 99%

Mechanical properties of Bacillus subtilis cell walls: effects of ions and lysozyme

1991

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“…Usually, the inhibition of peptidoglycan synthesis by addition of antibiotics to the growth medium promotes a lytic response in the culture (Rogers, 1980). No detailed studies of the effects of antibiotics on lactobacilli have been made, except for factors affecting lactic acid production (Wilkowske & Krienke, 195 1) and bactericidal efficiency (Torre & Davanzo, 1954;Arnold & Hold, 1955).…”

Section: Autolysis Of Whole Cellsmentioning

confidence: 99%

Cell wall and autolytic system of Lactobacillus helveticus ATCC 12046

Lortal¹,

Rousseau

Boyaval³

et al. 1991

Journal of General Microbiology

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The cell wall of Lactobacillus helveticus was found to have a three-layered structure when thin sections of whole cells or isolated cell walls were stained by various procedures and examined by electron microscopy. The main feature of the composition of isolated cell walls was a high protein content (about 48% of the cell wall dry weight) with a predominant 52 kDa protein. Peptidoglycan and what was considered as teichoic acids accounted for 36% and 14%, respectively, of the cell wall dry weight. The 52 kDa protein was apparently unglycosylated, located in the outer layer and noncovalently bound to the inner layers. Peptidoglycan was mostly assigned to the innermost layer. The conditions leading to autolysis of whole cells or isolated cell walls were determined, as well as the specificity of the autolysin involved in cell wall degradation. IntroductionLactobacillus helveticus is an important lactic acid bacterium that is involved in cheese technology (Accolas et al., 1980;Turner et al., 1983) and that has recently become the object of interest for genetic manipulation (Chassy, 1987;Sandine, 1987;Thomas & Collins, 1988). Its autolysis with the concomitant release of cytoplasmic proteases (Ezzat et al., 1986) is an essential feature of cheese maturation (Bie & Sjostrom, 1975a, b). A better understanding of the autolytic system of L. helveticus could perhaps offer a new way for an accelerated ripening of cheese. Ohmiya & Sat0 (1970) were the first to follow the autolysis of L. helveticus in technological conditions. After adding whole cells to an aseptic rennet curd, the release of DNA was noted and autolysed cells were clearly observed by electron microscopy. More recently, we promoted the autolysis of L. helveticus by suspending whole cells in dilute buffers (Lortal et al., 1989). A clear understanding of the autolytic system of L. helveticus implies, in particular, a better knowledge of the composition and structure of its cell wall, which have so far been investigated only to a limited extent (Ikawa & Snell, 1960;Baddiley & Davison, 1961 ; Williams, 1971). The main peptidoglycan amino acids were determined (Glu, Ala, Asp, Lys) as well as their respective percentage in the D-configuration (Ikawa & Snell, 1960). Previous studies also revealed the presence of glyceroltype teichoic acids (Baddiley & Davison, 1961) and neutral sugars (glucose, galactose but no rhamnose). Wall and membrane teichoic acids of L. helveticus were shown to have antigenic properties (Knox & Wicken, 1971). It has also been suggested that the cell wall of L. helveticus ATCC 10797 was composed of two layers with the outer layer presumably containing a predominant protein (Masuda & Kawata, 1983).In the work described here, a more detailed investigation of the morphology and composition of the cell wall of L. helveticus ATCC 12046 was undertaken. Moreover, the main characteristics of the autolytic system of this strain were investigated, in particular ways of promoting lysis, the effect of external factors, and the specificity of the autolytic...

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“…The sin (flaDi) mutation also reduced expression of a sigD-lacZ fusion gene constructed in the B. subtilis chromosome. Since the sigD-null mutant exhibits motility and autolysin deficiencies and filamentation, similar phenotypes in the sin (faDI) mutant may be caused by reduction in expression of the o'r protein.Peptidoglycan hydrolases are believed to be involved in important biological processes such as cell wall turnover (4,7,18,51) and cell separation (7,9,39) and to act as pacemaker and spacemaker enzymes for cell growth (51). Some of the peptidoglycan hydrolases can act as autolysins, thereby appearing to be potential suicide enzymes.…”

mentioning

confidence: 99%

“…Peptidoglycan hydrolases are believed to be involved in important biological processes such as cell wall turnover (4,7,18,51) and cell separation (7,9,39) and to act as pacemaker and spacemaker enzymes for cell growth (51). Some of the peptidoglycan hydrolases can act as autolysins, thereby appearing to be potential suicide enzymes.…”

mentioning

confidence: 99%

High-level transcription of the major Bacillus subtilis autolysin operon depends on expression of the sigma D gene and is affected by a sin (flaD) mutation

Kuroda

Sekiguchi

1993

J Bacteriol

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Transcription of the major BaciUlus subtilis autolysin gene (cwlB) was investigated. Deletion of the region upstream of the gene cluster 1ppX-cwbA-cwlB led to a loss of promoter activity. Primer extension analysis suggested that the cwlB operon is transcribed by Eo&E and Eo'A, the former transcripts being predominants at the exponential growth phase. Expression of the lppX-lacZ fusion gene was reduced by about 90% in a sigD-null mutant. A sin (flaDi) mutation caused a severe defect in transcription of the lppX-cwbA-cwlB operon. The sin (flaDi) mutation also reduced expression of a sigD-lacZ fusion gene constructed in the B. subtilis chromosome. Since the sigD-null mutant exhibits motility and autolysin deficiencies and filamentation, similar phenotypes in the sin (faDI) mutant may be caused by reduction in expression of the o'r protein.Peptidoglycan hydrolases are believed to be involved in important biological processes such as cell wall turnover (4,7,18,51) and cell separation (7,9,39) and to act as pacemaker and spacemaker enzymes for cell growth (51). Some of the peptidoglycan hydrolases can act as autolysins, thereby appearing to be potential suicide enzymes. This life and death dichotomy of function demands efficient and strict regulation of peptidoglycan hydrolase activity (18).Bacillus subtilis produces two autolysins, N-acetylmuramoyl-L-alanine amidase (the major autolysin) and endo-p-N-acetylglucosaminidase (glucosaminidase) (16,40). During sporulation, two other cell wall hydrolases, sporulationspecific amidase (s-amidase) and -y-D-glutamyl-L-mesodiaminopimelyl endopeptidase, are formed; the hydrolases are thought to be associated with the formation of cortex peptidoglycans (13). Some B. subtilis strains (YT-25 and K-77) produce extracellular endo-,B-N-acetylmuramidases (21, 34, 35). We previously reported the cloning of the cell wall hydrolase gene, cwlA (24). The product of this gene is not a major autolysin but an N-acetylmuramoyl-L-alanine amidase (10, 22) that is highly active on spore cortex peptidoglycans (10). Recently, we cloned and sequenced the major autolysin gene, cwlB, a mutant deficient in which is extremely resistant to cell lysis even after prolonged incubation (25 (6,9,30,41,47,50). The sigD and div-341 mutations are identical to the flaB and secA mutations, respectively (30, 42). The sacU(Hy) mutations, which map to adjacent genes (degU and degS), cause an increase in the production of degradative enzymes, poor development of competence, and lack of flagella (loss of motility) (8,33,37). The flaD (lyt) mutation causes similar * Corresponding author.phenotypes (an increase in alkaline protease, filamentous cell morphology, poor development of competence, and lack of flagella) (2, 36). Recently, we demonstrated that the flaD (lyt) gene is identical to the sin (sporulation inhibition) gene (11,45,46). Smith and colleagues found that Sin is a 14-kDa dual-function DNA-binding protein which has a negative function in sporulation (spoIL4, spoIIF, and spoIIG) and in aprE (major alkaline pr...

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Microbial Cell Walls and Membranes

Cited by 366 publications

References 0 publications

Mechanical properties of Bacillus subtilis cell walls: effects of ions and lysozyme

Mechanical properties of Bacillus subtilis cell walls: effects of ions and lysozyme

Cell wall and autolytic system of Lactobacillus helveticus ATCC 12046

High-level transcription of the major Bacillus subtilis autolysin operon depends on expression of the sigma D gene and is affected by a sin (flaD) mutation

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