Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “BACTERIOLYSIS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,027 records · Page 57Linked to original sources
PubMed1968

Control of amino sugar metabolism in Escherichia coli and isolation of mutants unable to degrade amino sugars.

1. Growth of Escherichia coli on glucosamine results in an induction of glucosamine 6-phosphate deaminase [2-amino-2-deoxy-d-glucose 6-phosphate ketol-isomerase (deaminating), EC 5.3.1.10] and a repression of glucosamine 6-phosphate synthetase (l-glutamine-d-fructose 6-phosphate aminotransferase, EC 2.6.1.16); glucose abolishes these control effects. 2. Growth of E. coli on N-acetylglucosamine results in an induction of N-acetylglucosamine 6-phosphate deacetylase and glucosamine 6-phosphate deaminase, and in a repression of glucosamine 6-phosphate synthetase; glucose diminishes these control effects. 3. The synthesis of amino sugar kinases (EC 2.7.1.8 and 2.7.1.9) is unaffected by growth on amino sugars. 4. Glucosamine 6-phosphate synthetase is inhibited by glucosamine 6-phosphate. 5. Mutants of E. coli that are unable to grow on N-acetylglucosamine have been isolated, and lack either N-acetylglucosamine 6-phosphate deacetylase (deacetylaseless) or glucosamine 6-phosphate deaminase (deaminaseless). Deacetylaseless mutants can grow on glucosamine but deaminaseless mutants cannot. 6. After growth on glucose, deacetylaseless mutants have a repressed glucosamine 6-phosphate synthetase and a super-induced glucosamine 6-phosphate deaminase; this may be related to an intracellular accumulation of acetylamino sugar that also occurs under these conditions. In one mutant the acetylamino sugar was shown to be partly as N-acetylglucosamine 6-phosphate. Deaminaseless mutants have no abnormal control effects after growth on glucose. 7. Addition of N-acetylglucosamine or glucosamine to cultures of a deaminaseless mutant caused inhibition of growth. Addition of N-acetylglucosamine to cultures of a deacetylaseless mutant caused lysis, and secondary mutants were isolated that did not lyse; most of these secondary mutants had lost glucosamine 6-phosphate deaminase and an uptake mechanism for N-acetylglucosamine. 8. Similar amounts of (14)C were incorporated from [1-(14)C]-glucosamine by cells of mutants and wild-type growing on broth. Cells of wild-type and a deaminaseless mutant incorporated (14)C from N-acetyl[1-(14)C]glucosamine more efficiently than from N[1-(14)C]-acetylglucosamine, incorporation from the latter being further decreased by acetate; cells of a deacetylaseless mutant showed a poor incorporation of both types of labelled N-acetylglucosamine.

Bacteriolysis↗
PubMed1969

Purification, properties and mechanism of action of a staphylolytic enzyme produced by Aeromonas hydrophila.

1. An enzyme produced by Aeromonas hydrophila and capable of lysing Staphylococcus aureus cells was purified 180-fold by gel filtration and chromatography on columns of AG-50 W resin. 2. Physical measurements on the purified enzyme suggest that it is a small basic protein with an isoelectric point between pH9.0 and pH9.5. 3. Maximum lytic activity was obtained in 20mm-tris-glycine buffer, pH8.5, at 45 degrees , with no detectable activity in the absence of a nitrogenous base. 4. The enzyme is active in the above buffer containing 1.5m-sucrose, and is useful for the preparation of protoplasts of Staphylococcus aureus. 5. Purified cell wall peptidoglycans of two strains of Staphylococcus aureus, differing in amino acid composition, were hydrolysed by the enzyme with the liberation of glycine oligopeptides, principally diglycine and triglycine. 6. Synthetic glycine oligopeptides larger than triglycine, but not polyglycine, were hydrolysed, as were a number of leucine-containing dipeptides and tripeptides, but no proteolytic activity could be demonstrated. 7. It is concluded that the enzyme is lytic towards Staphylococcus aureus because it splits the pentaglycine cross-links of the cell-wall peptidoglycan.

Aeromonas↗
PubMed1969

Effect of potassium ions on the attachment of polyribosomes to the membranes in lysates of exponential-phase cells of Bacillus amyloliquefaciens.

1. The distribution of ribosomal components between the soluble and membrane fractions of a preparation of exponential-phase cells of Bacillus amyloliquefaciens lysed with lysozyme in 0.05m-tris buffer, pH7.6, containing 0.01m-Mg(2+), was strongly influenced by the addition of K(+) to the buffer, in the range 0-0.1m. 2. In the absence of K(+), 37% of the ribosomal material was bound to the membrane and was not removed by repeated washing with the lysing buffer. The amount of bound material was progressively decreased on increasing the K(+) concentration to 0.1m, when only 5% of ribosomal components remained attached to the membrane. 3. About 87% of the material that remained bound to the washed membranes prepared in the absence of added K(+) was removed on suspension of the membranes in a buffer containing 0.1m-potassium chloride. 4. In the absence of K(+), washed membranes, containing no detectable ribosomal material, were able to re-attach no more than half as much material as was found associated with membranes in the same buffer immediately after lysis. 5. There was no evidence of binding of specific components to the membrane. 6. In the presence of 0.05m-tris buffer, pH7.6, maximum incorporation of amino acids into protein by B. amyloliquefaciens polyribosomes is effected in the presence of 0.01m-Mg(2+) and 0.07-0.1m-K(+), under which conditions less than 10% of the ribosomal material of a cell lysate would be membrane-bound.

Amino Acids↗
PubMed1970

Cell-wall thickening in Bacillus subtilis. Comparison of thickened and normal walls.

1. Incubation of Bacillus subtilis 168 trp in a glucose-amino acids-salts medium lacking tryptophan leads to an inhibition of cellular growth without affecting cell-wall synthesis. The cell walls increased approximately two- to three-fold in thickness and at the same time the amount of mucopeptide in the cells measured chemically increased to about the same extent. 2. Synthesis of mucopeptide and teichoic acid as measured by the extent of incorporation of radioactivity continued linearly for approximately 1h and then stopped. No reason was found for the strictly limited synthesis of the wall polymers. 3. The initial rates of incorporation of [(32)P]P(i) or [(3)H]alanine into teichoic acid and of (3)H-labelled amino acids into mucopeptide were not appreciably inhibited by the addition of chloramphenicol to the glucose-amino acids-salts medium. 4. There was no selective turnover of the mucopeptide synthesized by the cells in a medium lacking tryptophan on resumption of growth in a complete medium. 5. Wall synthesis taking place during the thickening process was similar to normal wall synthesis proceeding in growing cells. Walls of different thicknesses prepared from cells incubated for various times in incomplete medium did not differ qualitatively in composition. The products of autolysis of thickened walls were isolated and the analyses indicated a close similarity in the details of their mucopeptide structure compared with the mucopeptide of cells growing in the exponential phase.

Alanine↗
PubMed1970

Bacteriolytic enzymes from Staphylococcus aureus. Purification of an endo-beta-N-acetylglucosaminidase.

On cultivation of Staphylococcus aureus in a complex liquid medium, bacteriolytic activity is found extracellularly. The maximal amount was found at the end of the exponential growth phase in batch culture, but in continuous culture run under similar conditions the yield was doubled. Isoelectric focusing of dialysed crude culture supernatants showed that the bacteriolytic activity of all four strains studied (M18, 524, Wood 46 and Duncan) was heterogeneous. The most alkaline peak of activity (isoelectric point 9.5+/-0.1) was assayed against Micrococcus lysodeikticus turbidimetrically. This bacteriolytic activity was purified more than 70-fold after continuous dialysis by adsorption on CM-Sephadex, precipitation with ethanol, heat purification, isoelectric focusing and Sephadex G-100 chromatography. The purified enzyme (isoelectric point 9.6+/-0.1) was found to give a single band on polyacrylamide-gel and cellulose acetate electrophoresis and was devoid of all 14 staphylococcal enzymes and toxins assayed for. The molecular weight is 70000+/-5000 as estimated by Sephadex G-100 and G-200 chromatography. The marked instability of the partially and highly purified enzyme was investigated. The mode of action and some properties of this enzyme are given in the following papers (Wadström & Hisatsune, 1970; Wadström, 1970). These results indicate that this extracellular enzyme which is produced by several strains of S. aureus is not a ;lysozyme' (endo-beta-N-acetylmuramidase) as previously suggested, but an endo-beta-N-acetylglucosaminidase.

Adsorption↗
PubMed1970

Bacteriolytic enzymes from Staphylococcus aureus. Specificity of ction of endo-beta-N-acetylglucosaminidase.

The bacteriolytic enzyme with an isoelectric point of 9.5 that is produced by all strains of Staphylococcus aureus investigated was purified from strain M18 (Wadström & Hisatsune, 1970). This enzyme released reducing groups from cell walls of Micrococcus lysodeikticus and was thus shown to be a bacteriolytic hexosaminidase. Although dinitrophenylation and acid hydrolysis of cell walls hydrolysed by a partially purified enzyme gave DNP-alanine and DNP-glycine from staphylococcal peptidoglycan, which indicated the presence of a peptidase and probably also an N-acetylmuramyl-l-alanine amidase, hydrolysis of cell walls by the extensively purified enzyme did not give any DNP-amino acids. The enzyme digest was purified by Amberlite CG-120 and Sephadex G-10 chromatography. Reduction by sodium borohydride of the disaccharide obtained was followed by acid hydrolysis and paper chromatography. Glucosamine completely disappeared after this treatment and a new spot identical with glucosaminitol appeared. The muramic acid spot remained unchanged. The purified enzyme was found to be devoid of exo-beta-N-acetylglucosaminidase activity. These results are compatible with the action of a bacteriolytic endo-beta-N-acetylglucosaminidase. It is also proposed that this enzyme is probably identical with the staphylococcal lysozyme. The mode of action of this has not previously been investigated.

Alanine↗
PubMed1970

Bacteriolytic enzymes from Staphylococcus aureus. Properties of the endo-beta-N-acetylglucosaminidase.

An extracellular bacteriolytic endo-beta-N-acetylglucosaminidase has been purified and its specificity of action has been investigated (Wadström & Hisatsune, 1970a,b). Some enzymic properties, such as optimum pH for enzyme activity on whole cells and cell walls of Micrococcus lysodeikticus and Staphylococcus aureus and optimum pH for stability, have been studied. The activity was maximum in 0.05m-tris-hydrochloric acid buffer, pH7.0. A higher ionic strength inhibited cell-wall hydrolysis. Since the crude and purified enzymes were found to be unstable on storage, the stabilizing and inhibiting effects of several compounds were investigated. Several heavy metal ions inactivated the enzyme at very low concentrations. Thiol compounds stabilized and thiol-reacting compounds partly inhibited the activity. Crude and purified glucosaminidase was found to be heat-stable at acidic pH and unstable at alkaline pH as previously found for several lysozymes (endo-beta-N-acetylmuramidases). Other properties of the staphylococcal enzyme and hen's-egg-white lysozyme have been compared, since the modes of action of the two are quite similar (Wadström & Hisatsune, 1970b).

Bacteriolysis↗
PubMed1976

Membrane attachment of folded chromosome of Escherichia coli.

By fractionation of the envelope part of membrane-associated folded chromosomes it is shown that only the outer membrane is bound to the DNA. Experiments with the M-band technique suggest the presence of attachment points for the membrane also in membrane-released folded chromosomes.

Bacteriolysis↗
PubMed2005

Unravelling the structure of the pneumococcal autolytic lysozyme.

The LytC lysozyme of Streptococcus pneumoniae forms part of the autolytic system of this important pathogen. This enzyme is composed of a C-terminal CM (catalytic module), belonging to the GH25 family of glycosyl hydrolases, and an N-terminal CBM (choline-binding module), made of eleven homologous repeats, that specifically recognizes the choline residues that are present in pneumococcal teichoic and lipoteichoic acids. This arrangement inverts the general assembly pattern of the major pneumococcal autolysin, LytA, and the lytic enzymes encoded by pneumococcal bacteriophages that place the CBM (made of six repeats) at the C-terminus. In the present paper, a three-dimensional model of LytC built by homology modelling of each module and consistent with spectroscopic and hydrodynamic studies is shown. In addition, the putative catalytic-pair residues are identified. Despite the inversion in the modular arrangement, LytC and the bacteriophage-encoded Cpl-1 lysozyme most probably adopt a similar global fold. However, the distinct choline-binding ability and their substrate-binding surfaces may reflect a divergent evolution directed by the different roles played by them in the host (LytC) or in the bacteriophage (Cpl-1). The tight binding of LytC to the pneumococcal envelope, mediated by the acquisition of additional choline-binding repeats, could facilitate the regulation of the potentially suicidal activity of this autolysin. In contrast, a looser attachment of Cpl-1 to the cell wall and the establishment of more favourable interactions between its highly negatively charged catalytic surface and the positively charged chains of pneumococcal murein could enhance the lytic activity of the parasite-encoded enzyme and therefore liberation of the phage progeny.

Amino Acid Sequence↗
PubMed2003

Beyond lysis: how complement influences cell fate.

Complement is a central component of the innate immune system involved in protection against pathogens. For many years, complement has been known to cause death of targets, either indirectly by attracting and activating phagocytes or directly by formation of a membrane pore, the membrane attack complex. More recently, it has been recognized that complement may cause other 'non-classical' effects that may not directly be aimed at killing of pathogens. Products of complement activation collaborate with the adaptive immune system to enhance responses to antigens. The membrane attack complex of complement, apart from lysing cells, can also trigger diverse events in target cells that include cell activation, proliferation, resistance to subsequent complement attack and either resistance to, or induction of, apoptosis. Various complement products play important roles in signalling for clearance by phagocytes of apoptotic self cells. Here we review some of these non-classical activities of complement and stress the roles that they may play in maintaining the integrity of the organism.

Apoptosis↗
PubMed1998

Cell membrane integrity and lysis in Lactococcus lactis: the detection of a population of permeable cells in post-logarithmic phase cultures.

A method was developed that enabled an analysis of the proportion of permeable cells in a culture of Lactococcus lactis. This used the fluorescence of propidium iodide (PI) when in contact with DNA and the impermeability of the intact cell membrane to this compound. A permeability index was suggested that expresses the PI-induced fluorescence of a cell suspension as a percentage of the value obtained from wholly permeabilized cells after treatment with cetyltrimethylammonium bromide. This method was applied to the determination of cell permeability in death phase cultures. A large proportion of unlysed cells was freely permeable to PI, a finding that may have some significance for the investigation of the role of cell lysis in cheese maturation. This method is suggested as a useful addition to the techniques available for the study of cell damage in a variety of fields, and for the screening of cheese starter bacteria.

Bacteriolysis↗
PubMed1998

Specific assays for bacteria using phage mediated release of adenylate kinase.

A sensitive and rapid assay method for the specific detection of bacteria was developed using Escherichia coli and Salmonella newport as the test organisms. Bacteriophages were used to provide specific lysis of the bacteria and then the release of cell contents was measured by ATP bioluminescence. Increased sensitivity was obtained by focusing on the bacteria's adenylate kinase (AK) as the cell marker instead of ATP as conventionally used. Fewer than 10(3) E. coli cells could be readily detected in less than 1 h. Salmonella newport assays, although as sensitive, were slower and took up to 2 h. The effects of the culture medium, the phage, and the presence of non-specific bacteria were examined.

Adenylate Kinase↗
PubMed1999

A fast method for monitoring the colonization rate of lactobacilli in a meat model system.

A random amplified polymorphic DNA (RAPD) assay coupled to a fast and reproducible cell lysis method from Lactobacillus colonies were developed to type lactobacilli of different strains and species, with the aim of precisely enumerating each of the different Lactobacillus strains inoculated in a nutrient-rich environment, such as sausage meat batter. Colonization assays were carried out in an aseptic meat fermentation system for up to 14 d and the inoculated strains were challenged with mixtures of wild lactobacilli. The proportion of inoculated strains remaining at different times was compared with the total number of lactobacilli grown on MRS agar by RAPD. The colonization rate of the different strains tested was very different. The RAPD-fast lysis method developed is simple and, with a low cost per assay, could also be applied to other food fermentations.

Animals↗
PubMed2000

Characterization and mechanism of action of cerein 7, a bacteriocin produced by Bacillus cereus Bc7.

Cerein 7 is a peptidic antibiotic produced by Bacillus cereus Bc7 (CECT 5148) at the end of exponential growth but before sporulation onset. Cerein 7 has a broad spectrum of antibacterial activity against Gram-positive bacteria, but it is inactive against Gram-negative bacteria. The sequence of its amino-terminal end and its characteristics of hydrophobicity and molecular mass make cerein 7 unique among the bacteriocins produced by the soil bacterium B. cereus. In this paper a further characterization of cerein 7 is presented, it is shown that it can be classified as a Klaenhammer's class II bacteriocin and that its mode of action corresponds to that of a membrane-active compound.

Bacillus cereus↗
PubMed2000

Autolysis of dairy leuconostocs and detection of peptidoglycan hydrolases by renaturing SDS-PAGE.

The autolysis of lactic acid bacteria plays a major role during cheese ripening. The aim of this study was to evaluate the autolytic properties and peptidoglycan hydrolase content of dairy leuconostocs. Autolysis of 59 strains of dairy Leuconostoc was examined under starvation conditions in potassium phosphate buffer. The ability of dairy leuconostocs to lyse is strain dependant and not related to the species. The peptidoglycan hydrolase profile of Leuc. mesenteroides subsp. mesenteroides 10L was analysed by renaturing gel electrophoresis. Two major activity bands migrating at 41 and 52 kDa were observed. According to the specificity analysis, strain 10L seems to contain a glycosidase and an N-acetyl-muramyl-L-alanine amidase, or an endopeptidase. The peptidoglycan hydrolase profiles of various Leuconostoc species were also compared. Several peptidoglycan hydrolase activities could be detected in the different Leuconostoc species. Further characterization of the peptidoglycan hydrolases will help to control autolysis of leuconostocs in cheese.

Bacteriolysis↗
PubMed2001

Analysis of the role of bacterial endospore cortex structure in resistance properties and demonstration of its conservation amongst species.

AIMS: The aim of this work was to compare the chemical structure of the spore cortex of a range of species, and to determine any correlation between cortex structure and spore resistance properties. METHODS AND RESULTS: The fine chemical structure of the cortex of Bacillus subtilis, Bacillus megaterium, Bacillus cereus and Clostridium botulinum was examined by muropeptide analysis using reverse phase HPLC. There is a conserved basic structure between peptidoglycan of these species, with the only difference being the level of de-N-acetylation of an amino sugar. In order to determine if an alteration in cortex structure correlates with heat resistance properties, the peptidoglycan structure and properties of B. subtilis spores prepared under different conditions were compared. Peptidoglycan from spores prepared in Nutrient Broth (NB) showed reduction in single L-alanine substituted muramic acid to only 13.9% compared with 20.6% in CCY-grown spores. NB-prepared spores are also unstable, with 161-fold less heat resistance (60 min, 85 degrees C) and 43 times less Mn(2+) content than CCY-grown spores. Addition of MnCl(2) to NB led to a peptidoglycan profile similar to CCY-grown spores, sevenfold more heat resistance (60 min, 85 degrees C) and an 86-fold increase in Mn(2+) content. Addition of CCY salts to NB led all parameters to be comparable with CCY-grown spore levels. CONCLUSION: It has been shown that peptidoglycan structure is conserved in four spore-forming bacteria. Also, spore heat resistance is multifactorial and cannot be accounted for by any single parameter. SIGNIFICANCE AND IMPACT OF THE STUDY: Endospores made by diverse species most likely have common mechanisms of heat resistance. However, the molecular basis for their resistance remains elusive.

Amino Acids↗
PubMed2002

Autolytic phenotype of Lactococcus lactis strains isolated from traditional Tunisian dairy products.

AIMS: To evaluate the autolytic properties of Lactococcus lactis strains isolated from artisan Tunisian dairy products, their peptidoglycan hydrolase content and their activity spectrum. METHODS AND RESULTS: The autolytic phenotype of Lactococcus strains was evaluated under starvation conditions in potassium phosphate buffer. The results obtained highlighted a high degree of diversity among the strains analysed, allowing the identification of high and low autolytic Lactococcus lactis strains. Peptidoglycan hydrolase content was evaluated by renaturing SDS-PAGE using cells of Micrococcus lysodeikticus as a target for the enzymatic activity. A major activity band migrating at about 45 kDa was observed. The lytic activity, evaluated in the presence of different chemicals, was retained in 8% NaCl, 15 mmol l(-1) CaCl2, and in a pH range between 5 and 9.5. The substrate specificity of peptidoglycan hydrolase from Lactococcus strains was evaluated in renaturing SDS-PAGE incorporating cells of different bacterial species. The major autolysin of Lactococcus lactis was active against cells of Lactococcus lactis subsp. lactis, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus and Listeria monocytogenes. CONCLUSIONS: Autolytic activity is widely distributed in Lactococcus lactis and the rate of autolysis is strain-dependent. The major peptidoglycan hydrolase showed a wide spectrum of activity against several lactic acid bacteria and bacterial species involved in food-related infection. SIGNIFICANCE AND IMPACT OF THE STUDY: The autolytic phenotype of Lactococcus lactis strains isolated from Tunisian artisan dairy products has been determined, and the data obtained should allow the selection of strains of technological interest in the cheese-ripening process.

Bacteriolysis↗
PubMed2003

Autolytic activity and pediocin-induced lysis in Pediococcus acidilactici and Pediococcus pentosaceus strains.

AIMS: To evaluate the autolytic phenotype of Pediococcus acidilactici and P. pentosaceus, the peptidoglycan hydrolases content and the effect of pediocin AcH/PA-1 and autolysins on cell lysis. METHODS AND RESULTS: The autolytic phenotype of Pediococcus strains was evaluated under starvation conditions in potassium phosphate buffer. The strains tested showed an extent of autolysis ranging between 40 and 90% after 48 h of starvation at 37 degrees C. Peptidoglycan hydrolase content was evaluated by renaturing sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) using cells of Micrococcus lysodeikticus as a target for the enzymatic activity and a major activity band migrating at about 116 kDa was detected. Additional secondary lytic bands migrating in a range of molecular weight between 45 and 110 kDa were also detected. The lytic activity, evaluated in the presence of different chemicals, was retained in 15 mM CaCl2 and in a range of pH between 5 and 9.5 but was strongly reduced in presence of 8% NaCl and in the presence of protease inhibitors. The substrate specificity of peptidoglycan hydrolases of Pediococcus strains was evaluated in renaturing SDS-PAGE incorporating cells of different bacterial species. Lytic activity was detected against cells of Lactococcus lactis subsp. lactis, L. delbrueckii subsp. bulgaricus, Lactobacillus helveticus and Listeria monocytogenes. The interaction between pediocin AcH/PA-1 and autolysis was evaluated and a relevant effect of bacteriocin in cell-induced lysis was observed. CONCLUSIONS: The autolytic phenotype is widely distributed among P. acidilactici and P. pentosaceus and the rate of autolysis is high in the majority of the analysed strains. Several autolytic bands, detected by renaturing SDS-PAGE, retained their activity against several lactic acid bacteria and L. monocytogenes. SIGNIFICANCE AND IMPACT OF THE STUDY: The characterization of the autolytic phenotype of Pediococcus acidilactici and P. pentosaceus strains should expand the knowledge of their role in fermentation processes where these species occur as primary or secondary bacterial population.

Bacteriocins↗