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W S Wegener

Publications and source records attributed to W S Wegener.

9 recordsLinked to original sources
PubMed1979

Phospholipid metabolism in Neisseria gonorrhoeae: phospholipid hydrolysis in nongrowing cells.

Hydrolysis of cell envelope phospholipids was demonstrated in cells of both autolytic and nonautolytic strains of Neisseria gonorrhoeae that were labeled during growth in the presence of [3H] acetate. The label incorporated into the cellular phospholipids was located exclusively in the fatty acid acyl side chains. Labeled cells were incubated for 2 hr in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer, pH 8.5, containing various additions, and then examined for distribution of 3H in lipids. Ca++ selectively stimulated the deacylation of phosphatidylethanolamine (PE), whereas Mn++ stimulated the deacylation of phosphatidylglycerol (PG). Hydrolysis of phosphatidylethanolamine by phospholipase A was accompanied by the accumulation of lysophosphatidylethanolamine (LPE) and free fatty acids in the cells. Free fatty acids accumulated to a greater extent than lysophosphatidylethanolamine, suggesting that the latter was further hydrolyzed to glycerophosphorylethanolamine (GPE) and free fatty acids by a lysophospholipase. Methanol, ethanol, propanol, and isopropanol, added at concentrations which inhibited growth by 50%, stimulated phospholipase A, but not lysophospholipase activity. Differences in heat inactivation, metal ion requirements, and pH optima suggested that phospholipase A activities with phosphatidylethanolamine or phosphatidylglycerol as substrate and lysophospholipase may be separate enzymes.

Buffers↗
PubMed1978

Cell envelope of Neisseria gonorrhoeae: phospholipase activity and its relationship to autolysis.

The relationship between conditions which permit or inhibit cell lysis and those which promote phospholipid hydrolysis in Neisseria gonorrhoeae was investigated. Suspension of exponential-phase gonococci in buffer in the absence of divalent cations resulted in autolysis but not in phosphlipid hydrolysis. The addition of Ca2+ or Mg2+ to the buffer inhibited autolysis and markedly stimulated the hydrolysis of phosphatidylethanolamine. Incubation of cells in buffer at pH 6 inhibited both autolysis and phospholipid hydrolysis.

Bacteriolysis↗
PubMed1977

Cell envelope of Neisseria gonorrhoeae: relationship between autolysis in buffer and the hydrolysis of peptidoglycan.

Neisseria gonorrhoeae readily underwent autolysis when suspended in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffer at alkaline pH values. Autolysis was inhibited by the addition of Mg2+ or other divalent cations. Autolysis was also suppressed at acid pH (pH 6.0). Suspension of cells in buffer was accompanied by the hydrolysis of peptidoglycan. The rate of peptidoglycan hydrolysis in HEPES buffer was maximal at pH 8.5 and was similar in the presence or absence of Mg2+. Therefore, divalent cation stabilization against autolysis is not mediated by inhibition of peptidoglycan hydrolysis. Peptidoglycan hydrolysis occurred in HEPES buffer (pH 6.0), but at a rate that was 50% of the maximum. Incubation of cells with chloramphenicol or rifampin before suspension in HEPES buffer (pH 8.5) partially prevented autolysis; under these conditions, peptidoglycan hydrolysis still occurred, but at a reduced rate. Old and new peptidoglycans were hydrolyzed at similar rates. Peptidoglycan hydrolysis results in solubilization of both the peptide and glycan moieties.

Buffers↗
PubMed1977

Cell envelope of Neisseria gonorrhoeae: penicillin enhancement of peptidoglycan hydrolysis.

The addition of 10 microgram of penicillin G per ml to log-phase cultures of Neisseria gonorrhoeae JW-31 (minimum inhibitory concentration for penicillin G, less than 0.007 microgram/ml) resulted in cellular lysis after a lag of 30 min. Penicillin markedly decreased the rate of peptidoglycan synthesis and enhanced the rate of hydrolysis of existing peptidoglycan. Hydrolysis was initiated immediately after addition of penicillin; cellular lysis did not occur until a considerable percentage of the peptidoglycan had been degraded. Cellular lysis was not due to penicillin per se but resulted from inhibition of cell wall synthesis. When cells were grown in media buffered with N-2-hydroxyethyl piperazine-N'-2-ethanesulfonic acid at pH 6, penicillin did not cause lysis; however, at this pH, peptidoglycan hydrolysis occurred and cells lost viability at the same rate as in the control (pH 7.2). We suggest that the stability of gonococci grown at pH 6 is related to increased stability of the outer membrane. The penicillin-enhanced rate of peptidoglycan hydrolysis decreased approximately 50% at pH 6.0. Penicillin-enhanced lysis, peptidoglycan hydrolysis, and loss of viability were also markedly reduced in cells grown at 28 degrees C.

Bacterial Proteins↗
PubMed1976

Phospholipid composition and phospholipase A activity of Neisseria gonorrhoeae.

Exponential-phase cells of Neisseria gonorrhaeae 2686 were examined for phospholipid composition and for membrane-associated phospholipase A activity. When cells were harvested by centrifugation, washed, and lyophilized before extraction, approximately 74% of the total phospholipid was phosphatidylethanolamine, 18% was phosphatidylglycerol, 2% was cardiolipin, and 10% was lysophosphatidylethanolamine. However, when cells still suspended in growth medium were extracted, the amount of lysophosphatidylethanolamine decreased to approximately 1% of the phospholipid composition. This suggests that a gonococcal phospholipase A may be activated by conditions encountered during centrifugation and/or lyophilization of cells preceding extraction. Phospholipase A activity associated with cell membranes was assayed by measuring the conversion of tritiated phosphatidylethanolamine to lysophosphatidylethanolamine. Optimal activity was demonstrated in 10% methanol at pH 8.0 to 8.5, in the presence of calcium ions. The activity was both detergent sensitive and thermolabile. Comparisons of gonococcal colony types 1 and 4 showed no significant differences between the two types with respect to either phospholipid content or phospholipase A activity.

Calcium↗
PubMed1976

Selection of synchronous bacterial cultures by density sedimentation.

A procedure previously used to select synchronous cultures of Chlorella was found to produce similar results with the bacterium Lineola longa (Bacillus macroides). A midlog culture of L. longa was layered onto a 31-42% dialyzed Ficoll gradient and ceitruged at 51 000 3 g. The culture sedimented into a broad band in 30 min. Continued centrifugation failed to cause further migration. Cells taken from the top of the band and reinoculated into the broth in which they had previously grown, pH adjusted to 7.0, grew without a lag, doubled in optical density at the same rate as midlog cultures, and divided synchronously. Coulter counter sizing of these cells showed a doubling in volume just before division followed by a halving of volume after division. The major advantages of this method are the low osmolarity of Ficoll and the large volume of cells that can be separated.

Bacillus↗
PubMed1975

Plasmid DNA in virulent and avirulent gonococci.

The presence of covalently closed circular (CCC) DNA in virulent and avirulent colonial types of Neisseria gonorrhoeae strain 2686, and of type 3 colonies of strain F62 was investigated. CCC DNA was present in each, and the percentage of plasmid relative to total DNA was similar. The percentage of CCC DNA was similar in cells grown on a solid as compared with a liquid medium and in cells grown in the presence of varying concentrations of glucose. No correlation could be established between the presence of plasmid DNA and virulence of N. gonorrhoeae.

Culture Media↗