Base exchange and heat resistance in bacterial spores

Alderton, Gordon; Snell, Neva

doi:10.1016/0006-291x(63)90039-1

Cited by 95 publications

(48 citation statements)

References 8 publications

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“…The anisotropic swelling theory of cortex expansion during sporulation states that the cortex layer is first synthesized and then subsequent selective enzymatic cleavage of the peptide crosslinks results in radial expansion causing inward mechanical pressure on the spore core (1,56). Selective hydrolysis of the cortex during germination would release the physical constraint and allow uptake of water.…”

Section: Discussionmentioning

confidence: 99%

Structural analysis of Bacillus subtilis 168 endospore peptidoglycan and its role during differentiation

et al. 1996

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The structure of the endospore cell wall peptidoglycan of Bacillus subtilis has been examined. Spore peptidoglycan was produced by the development of a method based on chemical permeabilization of the spore coats and enzymatic hydrolysis of the peptidoglycan. The resulting muropeptides which were >97% pure were analyzed by reverse-phase high-performance liquid chromatography, amino acid analysis, and mass spectrometry. This revealed that 49% of the muramic acid residues in the glycan backbone were present in the ␦-lactam form which occurred predominantly every second muramic acid. The glycosidic bonds adjacent to the muramic acid ␦-lactam residues were resistant to the action of muramidases. Of the muramic acid residues, 25.7 and 23.3% were substituted with a tetrapeptide and a single L-alanine, respectively. Only 2% of the muramic acids had tripeptide side chains and may constitute the primordial cell wall, the remainder of the peptidoglycan being spore cortex. The spore peptidoglycan is very loosely cross-linked at only 2.9% of the muramic acid residues, a figure approximately 11-fold less than that of the vegetative cell wall. The peptidoglycan from strain AA110 (dacB) had fivefold-greater cross-linking (14.4%) than the wild type and an altered ratio of muramic acid substituents having 37.0, 46.3, and 12.3% ␦-lactam, tetrapeptide, and single L-alanine, respectively. This suggests a role for the DacB protein (penicillin-binding protein 5*) in cortex biosynthesis. The sporulationspecific putative peptidoglycan hydrolase CwlD plays a pivotal role in the establishment of the mature spore cortex structure since strain AA107 (cwlD) has spore peptidoglycan which is completely devoid of muramic acid ␦-lactam residues. Despite this drastic change in peptidoglycan structure, the spores are still stable but are unable to germinate. The role of ␦-lactam and other spore peptidoglycan structural features in the maintenance of dormancy, heat resistance, and germination is discussed. Dormant bacterial endospores formed by the genera Bacillus and Clostridium are the most resistant living structures known and are able to survive thousands if not millions of years (9). During the quiescent state, spores exhibit high-level resistance to many treatments, including heat, UV light, desiccation, and the action of deleterious chemicals. As a result of their resistance properties, spores are able to survive many food preservation and pasteurization procedures and thus cause huge problems to the food industry (11).Endospores are characterized by a relatively dehydrated protoplast encased in integument layers (20). The most prominent of the integuments are the spore coat layers which determine the physical properties of the spore surface and are responsible for resistance to enzymatic assault (56). However, the spore coats are not involved in the maintenance of dormancy and heat resistance (56). Between the spore coats and the protoplast membrane is a thick layer of bacterial peptidoglycan, consisting of two sublayers. Innermost is the ...

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Section: Discussionmentioning

confidence: 99%

Structural analysis of Bacillus subtilis 168 endospore peptidoglycan and its role during differentiation

et al. 1996

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“…Reduced heat resistance catalyzed by acid is reversed when the spores are reloaded with cations (Gould, 1984). The mechanism for the acid-catalyzed loss of heat resistance may be related to changes in spore hydration caused by changes in the ionic state of the spore cortex, which affects its osmotic and contraction state (Gould, 1984;Alderton, 1963).…”

Section: -2 Damage To the Spore Membranementioning

confidence: 99%

Importance of Considering Injured Microorganisms in Sterilization Validation

Shintani¹

2006

Biocontrol Sci.

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“…These include digestion of the asymmetric septum to permit prespore engulfment (5), cortex maturation (1,42), mother cell lysis, and cortex autolysis during germination (5). Mother cell lysis to release the mature endospore is the final characteristic morphological event that occurs during sporulation.…”

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confidence: 99%

Characterization of the involvement of two compensatory autolysins in mother cell lysis during sporulation of Bacillus subtilis 168

Smith

Foster

1995

J Bacteriol

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The 30-kDa sporulation-specific peptidoglycan hydrolase CwlC of Bacillus subtilis 168 was purified and characterized. It is an N-acetylmuramoyl-L-alanine amidase (amidase) that is associated with the mother cell wall of sporulating cells, and although it is secreted, it undergoes no N-terminal processing except removal of the initial methionine. It was found that mother cells of a strain insertionally inactivated in cwlC and lytC (the major vegetative amidase gene) did not lyse at the end of sporulation. Mutants with single mutations in cwlC or lytC lysed, and so the two autolysins must have mutually compensatory roles in mother cell lysis. Active CwlC and LytC are present at the time of mother cell lysis; however, reporter gene analysis revealed that lytC transcription ceases early in sporulation, and therefore the function that LytC has in mother cell lysis is performed by material remaining from presporulation expression. Autolytic enzymes similar in molecular mass to CwlC were detected in two other Bacillus species by their cross-reactivity with anti-CwlC antiserum.Autolysins, enzymes that hydrolyze bacterial cell wall peptidoglycan, are ubiquitous among bacteria (11), although their precise roles remain uncertain. In the spore-forming grampositive bacterium Bacillus subtilis, there may be 10 or more peptidoglycan hydrolases (8, 10). Such enzymes have been implicated in several functions during vegetative growth and sporulation (34,41).The differentiation process of sporulation involves a number of events of cell wall rearrangement, in which peptidoglycandegradative enzymes evidently play a fulcral role (10). These include digestion of the asymmetric septum to permit prespore engulfment (5), cortex maturation (1, 42), mother cell lysis, and cortex autolysis during germination (5). Mother cell lysis to release the mature endospore is the final characteristic morphological event that occurs during sporulation. A 30-kDa mother cell-associated autolysin appears during sporulation and has been postulated to be responsible for mother cell lysis (8). A gene, cwlC, which appears to encode this protein has been cloned and sequenced; the deduced gene product is a 255-amino-acid, 27-kDa peptide. Its expression is controlled by K (18), the mother cell-specific, late-sporulation sigma factor (6, 27). However, its role in sporulation was unknown, as the mother cells of a cwlC mutant still lyse (18).LytC is the major vegetative cell amidase of B. subtilis 168 and is also present during sporulation (8). The lytC gene is part of a three-gene operon, lytABC (25). lytR, which is transcribed divergently from lytABC, encodes a putative DNA-binding protein, which represses expression of itself and lytABC (25). lytA encodes an acidic protein that is thought to be membrane associated (20,25). lytB encodes a cell wall-associated modifier protein, which binds to the LytC amidase and enhances its activity (14). A study with a plasmid clone carrying a lytA::lacZ translational fusion suggested that, during vegetative growth, expression ...

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Base exchange and heat resistance in bacterial spores

Cited by 95 publications

References 8 publications

Structural analysis of Bacillus subtilis 168 endospore peptidoglycan and its role during differentiation

Structural analysis of Bacillus subtilis 168 endospore peptidoglycan and its role during differentiation

Importance of Considering Injured Microorganisms in Sterilization Validation

Characterization of the involvement of two compensatory autolysins in mother cell lysis during sporulation of Bacillus subtilis 168

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