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PubMed1982

The effect of benzyl penicillin on the ultrastructure of Neisseria gonorrhoeae.

Electron microscopy of Neisseria gonorrhoeae grown on solid medium with a subinhibitory concentration of penicillin suggested that the amount of penicillin reaching each pair of gonococci was different, as illustrated by the ultrastructural appearance of N, gonorrhoeae cells in the colony. This supports the view that the concentration of penicillin in different parts of the colony is not uniform, causing some cells to lyse while the others remain intact.

Bacteriolysis↗
PubMed1982

Production of inhibitors of lytic activity in the Micrococcaceae.

Eight Staphylococcus xylosus strains lacking lytic activity (LA) were found to excrete agar-diffusible factors inhibiting the LA of LA-positive strains of the same species. The same eight strains, when tested against LA-positive indicator strains from other species of Micrococcaceae, caused marked LA inhibition only of strains of S, saprophyticus and S. cohnii, both species closely related to S. xylosus. Micrococci and planococci, unlike staphylococci, do not normally show LA, yet Micrococcus lylae and M. sedentarius strains produced inhibitors effective against the LA of almost all the indicator strains, and planococci inhibited the LA of a few indicator strains. Micrococcus luteus strains caused LA inhibition of homologous indicators only, i.e. exceptional M. luteus strains exhibiting LA. Thus, a specific and a non-specific type of LA inhibition can be distinguished, and it is suggested that the apparent lack of LA might, in some instances, be explained by the simultaneous production of a specific inhibitor.

Bacteriolysis↗
PubMed1982

Mode of action of colicin S8.

The mode of action of colicin S8 has been studied and compared with that of other colicins. Two minutes after the addition of colicin S8 to bacteria a considerable proportion of the colicin is inaccessible to trypsin. Treatment of bacteria with colicin S8 renders them more sensitive to lysis by sodium dodecyl sulphate and also inhibits motility. Like colicins K and E1, colicin S8 provokes lysis of bacteria superinfected with bacteriophage T4. Colicin S8, unlike colicin E2, prevents replication of bacteriophage T4. The incorporation of isoleucine or uracil into bacteria is inhibited by colicin S8 but, unlike colicins K and E1, the effect is multiplicity-dependent. A rapid method of titration of colicin S8 is described. The results are discussed with emphasis on the possible rearrangements at the bacterial surface and the possibility that there is more than one type of specific receptor for colicin S8.

Bacteriolysis↗
PubMed1983

Protoplast and cytoplasmic membrane preparations from Streptococcus sanguis and Streptococcus mutans.

Protoplasts were prepared from Streptococcus sanguis and some S. mutans serotypes by use of lysozyme (EC 3.2.1.17) under particular conditions: cells had to be grown in DL-threonine (20 mM) and harvested in early exponential phase. The efficiency of protoplast formation was enhanced by two additional steps: plasmolysis (in 12% PEG), prior to addition of lysozyme, and a swirling phase, after the enzymic action. This procedure allowed us to obtain clean protoplasts, with only 0.5% contamination by bacterial cell walls. Up to 90% protoplast lysis was obtained in 0.5 M-NaCl. Cytoplasmic membrane purification was achieved by centrifugation on a glycerol cushion.

Bacteriological Techniques↗
PubMed1983

The bactericidal action of beta-lactam antibiotics on an autolysin-deficient strain of Bacillus subtilis.

An autolysin-deficient mutant of Bacillus subtilis was completely tolerant to 5 h incubation with 50-100 micrograms cycloserine ml-1 whereas the wild-type was rapidly lysed and killed by 12 micrograms ml-1. Lysis also did not occur when low concentrations of beta-lactams were added to exponentially growing cultures of the mutant, but over 90% of the bacteria were killed within 90-120 min. Protein, lipid and peptidoglycan synthesis as well as growth were inhibited after about 60 min. At this time, but not earlier, small amounts of these three cell components appeared in culture supernatants. Earlier, at about 20-30 min, the intracellular pools of amino acids started to decline rapidly and there was a temporary apparent increase in the rate of lipid synthesis. Neither of the latter phenomena occurred with cycloserine, with which protein and lipid synthesis declined only slowly and the rate of peptidoglycan synthesis was 80% inhibited within 30 min. Only occasional cells with damaged walls were seen 30-90 min after addition of either beta-lactams or cycloserine to the cultures. It thus seems unlikely that wall hydrolysis or penetration by residual autolysins in the mutant are responsible for mass cell death caused by the beta-lactams.

Amidohydrolases↗
PubMed1983

Mechanism of phage-induced lysis in pneumococci.

Earlier studies have suggested the possible role of host autolytic enzyme in the release of progeny phage from Dp-1 infected pneumococci. Several new experiments described here reinforce this notion. Specifically, the resistance of an autolysis-defective mutant to infection at low phage to cell ratios could be eliminated by prior 'coating' of the host bacteria with pneumococcal autolysin isolated from wild-type cells. Similar, productive infection was also possible by lowering the temperature of incubation to 30 degrees C, a condition that leads to a partial activation of the thermosensitive residual autolysin in the mutant cells. Other experiments, however, clearly indicate the role of the newly discovered phage-associated lysin (PAL), reported in the accompanying communication, in bacteriophage release and culture lysis; specifically, lysis was stimulated by reducing agents and inhibited by cardiolipin. It seems that both the host-related and the PAL activities are involved with Dp-1 induced lysis of pneumococci.

Bacteriolysis↗
PubMed1983

A phage-associated murein hydrolase in Streptococcus pneumoniae infected with bacteriophage Dp-1.

A phage-associated murein hydrolase activity capable of degrading pneumococcal cell walls was isolated and purified to homogeneity from the phage-induced lysate of an autolysis-defective pneumococcal mutant infected with the bacteriophage Dp-1. Some properties of the enzyme resembled those of the wild-type (host) pneumococcal murein hydrolase: cell walls prepared from ethanolamine-grown pneumococci were resistant to the enzyme; the activity was inhibited by the Forssman antigen and was sensitive to proteolytic enzymes. The phage-associated enzyme was not inhibited by antiserum prepared against the purified pneumococcal murein hydrolase; the activity was stimulated by reducing agents and was partially inhibited by cardiolipin. The subunit molecular weight of the phage-associated enzyme was somewhat smaller (31 000) than that of the pneumococcal hydrolase (35 000). This appears to be the first description of a phage-associated murein hydrolase activity in pneumococci.

Amidohydrolases↗
PubMed1984

An N-acetylmuramidase induced by PL-1 phage infection of Lactobacillus casei.

A lytic enzyme was isolated and purified from PL-1 phage-induced lysates of the host Lactobacillus casei ATCC 27092. The molecular weight of the enzyme was about 30000. Maximum activity on the lysis of the host cell walls occurred at pH 6.0-6.5 and at 45 degrees C. The enzyme activity was inhibited by heavy metal ions, SH- and serine-enzyme inhibitors and o-phenanthroline. The reducing end of the enzymic digest was muramic acid and the enzyme was considered to be an endo-N-acetylmuramidase. However, the enzyme differed from the other known N-acetylmuramidases including hen's egg-white lysozyme in several enzymic properties.

Bacteriolysis↗
PubMed1984

Lysis of Escherichia coli after infection with phiX174 depends on the regulation of the cellular autolytic system.

The relationship between the rate of lysis of Escherichia coli infected with bacteriophage phiX174 and the physiological state of the host bacteria was determined. The lysis rate was comparable to the growth rate only in cells grown in rich media, whereas in minimal medium it was much slower than the growth rate. Lysis of starved cells grown in minimal medium could not be induced by phiX174 although progeny phages were produced. Lysis of E. coli provoked by expression of the cloned phiX174 lysis gene could be prevented by MgSO4 concentrations which also prevented lysis by induced autolysins whereas prevention of lysis of phage-infected E. coli needed much higher concentrations of MgSO4. Prevention of lysis in the latter case did not reestablish viability of the infected cells whereas induction of the cloned phiX174 lysis gene allowed continued multiplication in the presence of MgSO4. Lysis of E. coli by expression of the cloned phiX174 lysis gene was suppressed at pH 6.0 and could be turned on immediately upon upshift to pH 6.8. Phage-infected cells lysed at pH 6.0. At pH 8.0, lysis of E. coli by phage infection or by the cloned lysis gene product was suppressed. pH downshifts in both cases were not followed by lysis. The results suggest that the phiX174 lysis gene product interacts in a reversible manner with the regulation of the autolytic system of E. coli.

Anti-Bacterial Agents↗
PubMed1984

Lysis of Vibrio cholerae cells: direct isolation of the outer membrane from whole cells by treatment with urea.

Cells of Vibrio cholerae underwent rapid autolysis when suspended in media of low osmolarity under non-growing conditions. Chaotropes like urea and guanidine. HCl which are potent protein denaturants caused complete and immediate lysis of whole cells. This unique sensitivity of V. cholerae to protein denaturants led to the development of a rapid method for the selective isolation of the outer membrane upon treatment of whole cells with urea. The composition of the outer membrane isolated from both whole cells and crude envelopes by treatment with urea was comparable with that of the outer membrane isolated by other conventional methods.

Bacterial Outer Membrane Proteins↗
PubMed1985

Lysis of Escherichia coli by beta-lactam antibiotics: deletion analysis of the role of penicillin-binding proteins 1A and 1B.

Deletions of the ponA and ponB genes of Escherichia coli have been constructed in vitro and recombined into the chromosome to produce strains that completely lack penicillin-binding protein 1A or penicillin-binding protein 1B. In each case a DNA fragment internal to the gene was replaced by a fragment encoding an antibiotic resistance. The ponA and ponB deletions can therefore be readily introduced into other E. coli strains by P1 transduction of the antibiotic resistance. Although the complete absence of penicillin-binding protein 1A or penicillin-binding protein 1B was tolerated, the absence of both of these proteins was shown to result in bacterial lysis.

Acyltransferases↗
PubMed1985

Fosfomycin causes transient lysis in Escherichia coli strains carrying fosfomycin-resistance plasmids.

Escherichia coli cells carrying fosfomycin-resistance plasmids show high levels of resistance towards this drug. However, the plasmid-carrying strains exhibited a transient lytic phase induced by fosfomycin when grown in rich liquid media. This lytic phase was not observed if the cells were grown in liquid minimal media. Fosfomycin-induced lysis depended on the accumulation of drug inside the bacteria, presumably as a result of the saturation of the fosfomycin modification system. Growth recovery after lysis was not due to drug inactivation in the culture medium and could be explained by selection of mutants showing impaired fosfomycin transport when high concentrations of fosfomycin were used. However, there was no selection of mutants with low drug concentrations.

Bacteriolysis↗
PubMed1985

Additional differentiating characters of the two subspecies of Staphylococcus hyicus.

Forty-five strains of Staphylococcus hyicus subsp. hyicus and 36 strains of S. hyicus subsp. chromogenes were examined for bacteriolytic activity with the same assay system previously used in taxonomic studies on staphylococci. The two subspecies differed from each other chiefly in that for optimal lytic activity S. hyicus subsp. hyicus strains required a higher salt concentration in the test medium than S. hyicus subsp. chromogenes strains. The lack of lytic activity on B15TP1 medium was a major difference between S. hyicus and S. aureus, and the lack of activity on TP2P medium was a major difference between S. hyicus and S. intermedius. Penicillin-binding proteins (PBPs) were studied in 40 S. hyicus strains. The S. hyicus subsp. hyicus strains had only one PBP (mol. wt 79 000) while the S. hyicus subsp. chromogenes strains had three distinct PBPs (mol. wts 84 000, 82 000 and 79 000).

Bacterial Proteins↗
PubMed1986

Effects of divalent cations and of phospholipase A activity on excretion of cloacin DF13 and lysis of host cells.

Induction of cloacin DF13 synthesis in Escherichia coli harbouring plasmid CloDF13 results in the release of cloacin DF13, inhibition of growth and ultimately in lysis of the host cells. Expression of the pCloDF13-encoded protein H is essential for both the release of cloacin DF13 and the lysis of the cells. The divalent cations Mg2+ and Ca2+ interfered with the mitomycin C-induced protein H-dependent lysis, but hardly affected the release of cloacin DF13. Essentially all of the bacteriocin was released from the cells before a detectable degradation of the peptidoglycan occurred, independent of the presence of mitomycin C. Experiments with phospholipase A mutants revealed that activation of detergent-resistant phospholipase A was essential for the export of cloacin DF13 across the outer membrane and the lysis of induced cells. Transport of cloacin DF13 across the cytoplasmic membrane was mainly dependent on protein H. A revised model for the excretion of cloacin DF13 is presented.

Bacterial Proteins↗
PubMed1986

Mutants of Streptococcus pneumoniae that contain a temperature-sensitive autolysin.

Two mutants of Streptococcus pneumoniae deficient in autolysin activity produced a protein that showed immunological identity with the N-acetyl-muramyl-L-alanyl-amidase present in the wild-type strain, when tested with antiserum obtained against this enzyme. The protein was produced by the mutant cultures grown either at 37 degrees C or at 30 degrees C, although only the cell extracts obtained at 30 degrees C showed significant cell wall hydrolysing activity. In contrast to the lysis resistance of these bacteria grown at 37 degrees C, mutant cultures grown at 30 degrees C exhibited significant degrees of autolysis when treated with detergent or cell wall inhibitors. Extracts of the mutant cultures contained a cell wall hydrolysing activity that was rapidly inactivated during incubation at 37 degrees C.

Amidohydrolases↗
PubMed1987

Characterization of a Pseudomonas aeruginosa transposon insertion mutant with defective release of exoenzymes.

A Pseudomonas aeruginosa transposon insertion mutant with defective release of several exoenzymes has been characterized. The Tn5-751 insertion mutation was located in the previously described xcp-1 locus at 0 min on the chromosomal map and caused several exoenzymes to remain in cell-bound form. At least one of the exoenzymes, elastase, was accumulated in the periplasmic space. The periplasmic elastase had the same Mr as the extracellular enzyme produced by the wild-type strain. The virulence of the mutant was comparable to that of wild-type strains in experimental burn infection in mice. The presence of an easily selectable antibiotic resistance marker in the xcp-1 locus offers the possibility of cloning the gene(s) involved in exoprotein secretion.

ADP Ribose Transferases↗
PubMed1987

Thermosensitive Bacillus subtilis mutants which lyse at the non-permissive temperature.

A collection of 655 thermosensitive mutants of Bacillus subtilis 168, obtained by indirect selection, was screened for those lysing at the non-permissive temperature. Thirty-three mutations thus identified were distributed by transformation into eight linkage groups designated lssA to lssH. The distribution was non-random. With the exception of group A, all groups were small, suggesting that mutations identified in each of them may map in one gene only. Linkage groups identified here were mapped in four different regions of the B. subtilis chromosome and their positions relative to reference markers were the following: (i) aroI-lssA-dal-purB; (ii) metC-lssB-lssC-furA-pyrE-cysC-lssD; (iii) lssF-gtaA-lssG-hisA-lssH-cysB; and (iv) cysA-lssE-dnaC-purA. Kinetics of N-acetyl-D-[1-14C]glucosamine incorporation revealed that groups A, B, C, D and F are deficient in peptidoglycan synthesis at the restrictive temperature. In group G, anomalies at the cell wall level were suggested by incorporation and growth curves. It appears that in almost all known cases, thermosensitive lysis mutations in B. subtilis either affect genes involved in peptidoglycan synthesis or lead, more or less directly, to induction of prophages.

Bacillus subtilis↗