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At least 1,207 records · Page 67Linked to original sources
PubMed1987

Bacteriolytic activity of seminalplasmin.

Seminalplasmin, an antimicrobial protein from bovine seminal plasma, lysed both Gram-positive and Gram-negative bacteria but not Candida albicans. The lytic activity was not lysozyme-like and was not affected by inhibitors of RNA or protein synthesis or by azide; it was strongly inhibited by divalent cations like Ca2+, Mn2+ and Mg2+ at millimolar concentrations. Maximum lysis of Escherichia coli was obtained at 37 degrees C; heat treatment of E. coli drastically reduced its susceptibility to lysis by seminalplasmin. E. coli cells in the stationary phase of growth were lysed much less than those in the exponential phase, and those grown in an enriched medium were lysed much more than those grown in a minimal medium. It appears that the lytic activity of seminalplasmin is due to the activation of an autolysin.

Anti-Bacterial Agents↗
PubMed1987

A mutant of Streptococcus pneumoniae that exhibits thermosensitive penicillin tolerance and the paradoxical effect.

Mutants of Streptococcus pneumoniae that contain active autolysin and yet cannot be induced to lyse during treatment with penicillin (Lyt+Tol+ mutants) have been described. We have now shown that these mutants are temperature dependent (32 degrees C); at 37 degrees C these bacteria underwent penicillin-induced lysis. In addition, mutants at the lysis-permissive temperature showed the so-called 'paradoxical response' to penicillin. Temperature shift experiments indicated that the change from tolerant to lytic response or vice versa is a fast process. No differences were detected in autolysin specific activity or in the kinetics of inhibition of protein, peptidoglycan and teichoic acid syntheses in cells treated with penicillin at 32 and 37 degrees C. The results of genetic crosses indicated that the thermosensitivity of penicillin-induced autolysis in the Lyt+Tol+ mutants is not a property of the autolytic enzyme itself. The observations suggest that the thermosensitive process in the mutants represents either a step(s) in autolysin regulation or involves some difference in the structure of the cell walls produced at 32 degrees C versus 37 degrees C.

Bacteriolysis↗
PubMed1988

Bacteriophage X-2: a filamentous phage lysing IncX-plasmid-harbouring bacterial strains.

Phage X-2, a filamentous rod about 950 nm in length, was isolated from sewage as plating on strains of Escherichia coli, Salmonella typhimurium or Serratia marcescens carrying either the IncX plasmid R6K, or the unique plasmid R775. Phage X-2 differs morphologically from a previously described very broad host range filamentous phage X which also lyses plasmid R6K-carrying strains and the phages differ in their resistance to inactivation by diethyl ether. Phage X-2 is serologically unrelated to phage X and the X-like phages IKe and I2-2. The adsorption site of the phage on the plasmid-bearing strains could not be determined but evidence implicating conjugative pili is presented.

Bacteriolysis↗
PubMed1991

Cytolysis of Bacillus subtilis by Fusarium oxysporum.

Growth of Fusarium oxysporum on heat-killed Bacillus subtilis cells was accompanied by the loss of bacterial cytoplasmic contents, and this 'cytolysis' could be catalysed in heat-treated bacteria by the fungal culture fluids. In electron micrographs the bacterial walls appeared undamaged, and the absence of wall-lytic enzymes was confirmed by use of isolated bacterial walls as substrate. Appearance of cytolytic activity in cultures was paralleled by the production of proteolytic activity in the cultures. Proteolysis and cytolysis had similar pH optima at 8.8-9.0. Cultures grown on casein, but not glucose, produced high cytolytic activity. Rapid cytolysis occurred when heat-treated B. subtilis cells were incubated with trypsin, subtilisin or pronase E. Viable bacteria, however, were not attacked, either by concentrated culture fluids or by the commercial protease preparations.

Bacillus subtilis↗
PubMed1991

A localization index for distinction between extracellular and intracellular antigens of Mycobacterium tuberculosis.

A series of mycobacterial antigens were quantified by immunoelectrophoresis, enzyme-linked immunosorbent assays, or SDS-PAGE with immunoblotting using antisera against purified mycobacterial antigens. The antigens showed a characteristic distribution profile. Some had a marked quantitative dominance in the culture fluid while others had a marked dominance in sonicates of whole washed bacilli. The majority of the antigens tested could thus be located and grouped as either secreted or cytoplasmic in terms of a localization index (LI) which is described. A 5-week-old Mycobacterium tuberculosis culture fluid preparation with a low degree of lysis was valuable in the delineation of localization indexes. The various secreted antigens showed a great span in LI values, from 5 to 1000. This variation may express different degrees of secretion efficiency or differences in tendency to adhere to the bacterial surface. The identification of proteins as extracellular or cytosolic according to their LI values was in agreement for cultures of M. tuberculosis with a low degree of lysis and cultures of M. bovis BCG and M. bovis AN-5 with significant lysis of the bacterial cells.

Antigens, Bacterial↗
PubMed1991

Bacteriolytic effect of teicoplanin.

The glycopeptide antibiotic teicoplanin belongs to the same group as vancomycin and ristocetin and is a valuable tool for studying the autolytic system of sensitive Gram-positive bacteria. Teicoplanin, at a concentration of 1 microgram ml-1, caused rapid lysis of exponential phase cells of Streptococcus faecalis. Bacillus spp. were most sensitive to the antibiotic; effective lysis occurred at 0.1 microgram teicoplanin ml-1. The bacteriolytic effect depended on the antibiotic concentration, the growth phase and growth rate of the target organism. Antibiotic added to overnight cultures did not cause lysis. Mg2+ (50 mM) was unable to prevent lysis. Mutants with decreased autolytic activity were more resistant to teicoplanin and lysed more slowly than the wild-type. Growth of bacteria in slightly acidic medium protected the cells against the lytic effect of teicoplanin typically observed at pH 7 or 8. This pH-dependent antibiotic tolerance was demonstrated with both bacilli and streptococci. Bacterial lysis was prevented by the presence of Ac-L-Lys(Ac)-D-Ala-D-Ala and normal growth was observed when this peptide was added simultaneously with teicoplanin. Bacteria pretreated with teicoplanin, washed and transferred to fresh medium or buffers behaved as if the antibiotic was still present; in neutral or slightly alkaline conditions strong lysis occurred, whereas in acidic buffer only bacteriostasis was observed. In contrast to vancomycin, teicoplanin induced some lysis of bacteria in hypertonic media, presumably by affecting the integrity of the cell membrane.

Amino Acid Sequence↗
PubMed1991

Multivariate analyses of fatty acid data from whole-cell methanolysates of Prevotella, Bacteroides and Porphyromonas spp.

The genus Bacteroides contains a number of biochemically and physiologically heterogeneous groups of organisms and needs taxonomic revision. In this study cellular fatty acids from a number of Bacteroides spp. were identified and quantified using gas chromatography and gas chromatography-mass spectrometry. The chemical data were then subjected to principal components analysis. In B. fragilis, which is the type species of the genus Bacteroides, C3-OH-iso17 was the predominant fatty acid (38.0%) and Cante15 was present in higher amounts (32.7%) than Ciso15 (14.6%). B. fragilis thus differed from all the other species examined: Prevotella (Bacteroides) buccae, P. (B.) oralis, P. (B.) oris, P. (B.) disiens, P. (B.) veroralis, P. (B.) heparinolytica and Porphyromonas (Bacteroides) endodontalis. Principal components analysis also enabled the closely related P. buccae, P. oralis and P. oris to be differentiated.

Bacteriolysis↗
PubMed1992

Calcium regulation of growth and differentiation in Streptococcus pneumoniae.

Streptococcus pneumoniae requires 0.15 mM-Ca2+ in the medium for optimal growth. Increasing the Ca2+ concentration to 1 mM triggers either a differentiative state, competence for genetic transformation during exponential growth, or partial lysis as soon as the cultures enter stationary phase. Genetic and physiological data both suggest that these responses are under the control of activator(s), excreted in the presence of high Ca2+ concentrations. 45Ca2+ transport is also stimulated by the activator(s). The amiloride derivative 2',4'-dimethylbenzamil (DMB) inhibits 45Ca2+ transport and prevents lysis and competence development. This provides evidence in favour of the involvement of Ca2+ transport in competence and culture lysis. On the other hand, addition of DNA to a competent culture prevents lysis of wild-type bacteria while a mutant, defective for DNA uptake, is not protected from lysis by exogenous DNA. An hypothesis is proposed for competence induction as a global metabolic response to Ca2+, under the control of competence factor.

Amiloride↗
PubMed1992

Antibodies recognizing a variety of different structural motifs on meningococcal Lip antigen fail to demonstrate bactericidal activity.

The neisserial Lip antigen is a conserved antigen associated with the pathogenic Neisseria species, and is composed of multiple repeats of a consensus pentapeptide. A series of monoclonal antibodies reacting with meningococcal Lip antigen were subjected to epitope mapping, using solid-phase synthetic peptides based on the consensus repeat sequence. The antibodies were found to recognize different continuous epitopes based on the consensus sequence. One monoclonal antibody was utilized in affinity chromatography to obtain purified Lip antigen and the antigen was used for immunization of mice. The resulting antisera did not recognize Lip antigen on Western blots but reacted specifically with Lip antigen in immune precipitation experiments, indicating that the predominant polyclonal immune response was directed against conformational epitopes. Despite the diversity of both continuous and conformational epitopes recognized by the antibodies produced, none of the antibodies demonstrated the ability to promote complement-mediated bactericidal activity. Thus despite its initial apparent promise as a potential vaccine candidate the case for the inclusion of Lip antigen in vaccine formulation cannot be supported at present.

Amino Acid Sequence↗
PubMed1997

Bacteriophage T4 development depends on the physiology of its host Escherichia coli.

Several parameters of phage T4 adsorption to and growth in Escherichia coli B/r were determined. All changed monotonously with the bacterial growth rate (mu), which was modified by nutritional conditions. Adsorption rate was faster at higher mu values, positively correlated to cell size, and increased by pretreatment with low penicillin (Pn) concentrations; it was directly proportional to total cellular surface area, indicating a constant density of T4 receptors on cell envelopes irrespective of growth conditions. Parameters of phage development and cell lysis were mu-dependent. The rate of phage release and burst size increased, while the eclipse and latent periods decreased with increasing mu. Differentiation between the contribution of several physiological parameters to the development of T4 was performed by manipulating the host cells. A competitive inhibitor of glucose uptake, methyl alpha-D-glucoside, was exploited to reduce the growth rate in the same effective carbon source. Synchronous cells were obtained by the "baby-machine' and large cells were obtained by pretreatment with low Pn concentrations. Lysis was delayed by superinfection, and DNA content and concentration were modified by growing a thy mutant in limiting thymine concentrations. The results indicate that burst size is not limited by cell size or DNA composition, nor directly by the rate of metabolism, but rather by the rates of synthesis and assembly of phage components and by lysis time. The rates of synthesis and assembly of phage components seem to depend on the content of the protein-synthesizing system and lysis time seems to depend on cellular dimensions.

Adsorption↗
PubMed1998

Biofilm susceptibility to bacteriophage attack: the role of phage-borne polysaccharide depolymerase.

Biofilm bacteria Enterobacter agglomerans 53b and Serratia marcescens Serr were isolated from a food processing factory. A bacteriophage (SF153b), which could infect and lyse strain 53b, was isolated from sewage. This has been shown to possess a polysaccharide depolymerase enzyme specific for the exopolysaccharide (EPS) of strain 53b. Using batch culture and chemostat-linked Modified Robbins Device systems it was observed that SF153b could degrade the EPS of a mono-species biofilm (strain 53b) and infect the cells. The disruption of the biofilm by phage was a combination of EPS degradation by the depolymerase and infection and subsequent cell lysis by the phage. Strain Serr biofilms were not susceptible to the phage and the biofilm EPS was not degraded by the phage glycanase, with the result that the biofilm was unaffected by the addition of SF153b phage. Scanning electron microscopy confirmed that specific phage could extensively degrade susceptible biofilms and continue to infect biofilm bacteria whilst EPS degradation was occurring.

Bacteriolysis↗
PubMed1998

Antibacterial action of dipeptides containing an inhibitor of glucosamine-6-phosphate isomerase.

Several dipeptides, containing the N3-(4-methoxyfumaroyl)-L-2,3-diaminopropanoic acid (FMDP) moiety linked to protein and non-protein amino acids, exhibited a strong growth-inhibitory and bactericidal effect against Bacillus subtilis. FMDP-dipeptides were efficiently transported into bacterial cells by a di-tripeptide permease and subsequently cleaved by intracellular Mn2+/Co2+-dependent peptidases. Cleavage rates [0.1-5.6 micromol min-1 (mg protein)-1] were about two orders of magnitude lower than transport rates [40-200 micromol min-1 (mg dry wt)-1]. The released FMDP inactivated glucosamine-6-phosphate (GlcN-6-P) isomerase, an enzyme catalysing the first committed step in a biosynthetic pathway leading to amino sugar-nucleotide precursors of bacterial peptidoglycan. Inhibition of GlcN-6-P isomerase precluded peptidoglycan biosynthesis and resulted in a strong bacteriolytic effect. Results of the studies on consequences of GlcN-6-P isomerase inhibition upon the action of FMDP-dipeptides provided evidence demonstrating that the lack of endogenous GlcN-6-P could be a reason for the triggering of bacterial autolysis. Peptides containing the inhibitors of GlcN-6-P isomerase are one of the very few antimicrobial agents known that exhibit both bactericidal and fungicidal effects.

Aldose-Ketose Isomerases↗
PubMed1998

Molecular characterization of an autolytic amidase of Listeria monocytogenes EGD.

The gene encoding a 102 kDa autolysin has been cloned from an expression library of Listeria monocytogenes EGD genomic DNA, using a direct screening protocol. The encoded protein has two domains, an N-terminal enzymic domain showing a high level of homology to the amidase domain of the major autolysin (atl) of Staphylococcus aureus, and a C-terminal, putative cell-wall-binding domain containing four imperfect direct repeats. In order to examine the role of the enzyme, the autolysin-encoding gene was insertionally inactivated by site-specific integration of a temperature sensitive plasmid. The enzyme accounts for 66% of the total lytic enzyme activity when L. monocytogenes walls are used as substrate and several of the major autolytic bands are missing on renaturing gels when compared to the wild-type. The enzyme does not appear to be directly involved in cell separation but has a role in motility. Characterization of the recombinant enzyme expressed in Escherichia coli has revealed it to be an amidase and to be able to hydrolyse a range of peptidoglycan substrates.

Amidohydrolases↗
PubMed1999

Physiological characterization of Streptococcus bovis mutants that can resist 2-deoxyglucose-induced lysis.

Streptococcus bovis JB1 does not normally lyse, but stationary phase lysis can be induced by including 2-deoxyglucose (2DG) in the growth medium. Isolates deficient in glucose/2DG phosphotransferase activity (PTS-) also lysed when 2DG was present (Lys+) and this result indicated that 2DG phosphorylation via the PTS was not an obligate requirement for 2DG-induced lysis. Cells and cell walls from 2DG-grown cultures lysed faster when proteinase K was added, but glucose-grown cultures and cell walls were not affected. A lipoteichoic acid (LTA) extract (aqueous phase from hot phenol treatment) from glucose-grown cells inhibited the lysis of 2DG-grown cultures, but a similar extract prepared from 2DG-grown cells was without effect. Thin-layer chromatography and differential staining indicated that wild-type and Lys+ PTS- cells incorporated 2DG into LTA, but lysis-resistant cultures (Lys- PTS+ and Lys- PTS-) did not. LTA from lysis-resistant (Lys- PTS+ and Lys- PTS-) cells grown with glucose and 2DG also prevented 2DG-dependent lysis of the wild-type. LTA could not inhibit degradation of cell walls isolated from 2DG-grown cultures, but LTA inhibited the lysis of Micrococcus lysodeikticus (Micrococcus luteus) cells that were exposed to supernatants from 2DG-grown S. bovis cultures. Group D streptococci (including S. bovis) normally have an alpha-1,2 linked glucose disaccharide (kojibiose) in their LTA, but kojibiose cannot be synthesized from 2DG. This observation suggested that the kojibiose moiety of LTA was involved in autolysin inactivation. Wild-type S. bovis had ATP- as well as PEP-dependent mechanisms of 2DG phosphorylation and one lysis-resistant phenotype (Lys- PTS-) had reduced levels of both activities. However, the Lys- PTS+ phenotype was still able to phosphorylate 2DG via ATP and PEP and this result indicated that some other step of 2DG incorporation into LTA was being inhibited. Based on these results, growth in the presence of 2DG appears to prevent synthesis of normal LTA, which is involved in the regulation of autolytic enzymes.

Antimetabolites↗
PubMed2002

Fast lysis of Escherichia coli filament cells requires differentiation of potential division sites.

Periodic activation of zonal peptidoglycan (murein) synthesis at division sites in Escherichia coli has been reported recently. Zonal synthesis is responsible for septum formation, whereas elongation of the cell sacculus is performed by diffuse insertion of precursors. Zonal synthesis can be triggered in ftsA, ftsQ and ftsI (pbpB) division mutants growing as filaments at the restrictive temperature, but not in ftsZ mutant strains. The lytic response to beta-lactams of cells able or unable to periodically trigger a zonal mode of murein synthesis could be substantially different. Therefore, we investigated the response to the bacteriolytic beta-lactam cefsulodin of ftsZ and ftsI mutants growing at the restrictive (42 degrees C) temperature. The ftsI cells lysed early and quickly after addition of the antibiotic. Sacculi of lysed cells were transversely cut in a very sharp way. In contrast the ftsZ strain lysed late and slowly after addition of the antibiotic and sacculi showed a generalized weakening of the murein network and extended breaks with a frayed appearance. No transversely cut sacculi comparable to those seen in the ftsI samples were found. Our results strongly support that beta-lactam-induced lysis occurs preferentially at division sites because of the activation of zonal murein synthesis at the initiation of septation.

Bacterial Proteins↗