Some features of the bacterial membrane studied with the aid of a new fractionation technique

Effect of different treatments on the activity of the heat labile enterotoxin of Escherichia coli F11(P155)

A whole cell lysate preparation of the Escherichia coli strain F11(P155) was treated with the following agents: heat (60 degrees C for 30 minutes), pronase, lipase, amylase, formalin (0.1%), sodium lauryl sulfate (0.05%) and sarkosyl NL30 (0.05%). Except for the amylase treatment, the treated whole cell lysate was inactivated when tested in rabbit gut loops or on Chinese hamster ovary cells. The preparations treated with heat or formalin could be used to produce a neutralizing antiserum or could remove the neutralizing capacity of an anti-F11(P155) serum. Finally, the attempt to demonstrate enterotoxicity with the cytoplasmic membrane of the bacterial cell failed.

Isolation of DNA-membrane complex in Bacillus subtilis

A DNA-membrane complex of Bacillus subtilis was separated from the bulk of the membrane by CsCl-sucrose double gradient centrifugation. The complex has a CsCl-sucrose buoyant density of 1.35-1.45 g/cm(3). Gel electrophoretic analyses show that the complex has about 5% of the whole membrane proteins and contains proteins unique to the complex as well as a small amount of membrane proteins. DNA in the complex is enriched for a genetic marker close to the origin (pur A16) and for one near the terminus (metB5). Artifactual formation of the complex during the lysate preparation was shown to be unlikely.

Turnover of phosphatidylglycerol in Escherichia coli

In growing cultures of Escherichia coli, the nonacylated glycerol of phosphatidylglycerol (PG) is labeled more rapidly than is the acylated glycerol. This is, in part, due to a rapid exchange reaction of the nonacylated glycerol. Only some of the PG molecules undergo this reaction while others are stable. Using a mutant unable to make glycerophosphate, we have shown that the nonacylated glycerol of PG can exchange with non-phosphorylated glycerol.

Solubilization of the cytoplasmic membrane of Escherichia coli by the ionic detergent sodium-lauryl sarcosinate

The sensitivity of the outer and cytoplasmic membranes of Escherichia coli to detergent was examined by isopycnic sucrose density gradient centrifugation. Sodium lauryl sarcosinate (Sarkosyl) was found to disrupt the cytoplasmic membrane selectively under conditions in which Triton X-100 and dodecyl sodium sulfate solubilized all membrane protein. These results were verified by gel electrophoresis; membrane proteins solubilized by Sarkosyl were identical to those of the cytoplasmic membrane. The presence of Mg(2+) during treatment with Sarkosyl was found to afford partial protection of the cytoplasmic membrane from dissolution.

Metabolism of phosphatidylglycerol, phosphatidylethanolamine, and cardiolipin of Bacillus stearothermophilus

The total phospholipid content of Bacillus stearothermophilus was constant during exponential growth, increased during the transition from the exponential to stationary phase of growth, and then slowly increased during the stationary phase. The first increase was a result of an increase in phosphatidylethanolamine; the second was a result of an increase in cardiolipin. Cessation of aeration of an exponentially growing culture or suspension in a nongrowth medium resulted in an immediate reduction in the rate of total phospholipid and phosphatidylethanolamine synthesis and a quantitative conversion of phosphatidylglycerol to cardiolipin. Cardiolipin appeared to be synthesized by the direct conversion of two molecules of phosphatidylglycerol to cardiolipin. After a 20-min pulse of (32)P, phosphatidylglycerol showed the most rapid loss of (32)P followed by cardiolipin, whereas phosphatidylethanolamine did not lose (32)P. The loss of (32)P from the total lipid pool, phosphatidylglycerol, and cardiolipin was biphasic, with rapid loss during the first two bacterial doublings followed by a greatly reduced rate of loss. The major loss of (32)P from the total phospholipid pool appeared to be by breakdown of cardiolipin. The loss of (32)P from the lipid pool was energy dependent (i.e., did not occur under anaerobic conditions or in the absence of an energy source) and was dependent on some factor other than the concentration of cardiolipin in the cells. The apparent conversion of phosphatidylglycerol to cardiolipin was independent of energy metabolism. Chloramphenicol reduced the rate of turnover of both phosphatidylglycerol and cardiolipin. The rate of lipid synthesis (all phospholipid components) was constant for about 10 min after the addition of chloramphenicol but diminished markedly after 20 min. Turnover of (32)P incorporated into phospholipid during a 30-min period prior to the addition of chloramphenicol was more rapid after the removal of chloramphenicol than that of (32)P incorporated during a 30-min period in the presence of chloramphenicol.

Some unique properties of the deoxyribonucleic acid-bearing portion of the bacterial membrane

By using the M-band technique we have shown that portions of the membranes of Bacillus megaterium and Escherichia coli vary in their affinity for magnesium-Sarkosyl crystals and in phospholipid composition. The portion to which deoxyribonucleic acid is attached comprises as little as 4% of the total cell membrane, has a particularly high degree of affinity for magnesium-Sarkosyl crystals, and is rich in phosphatidylethanolamine. The M-band fractionation does not depend on the use of lysozyme.

Isolation and properties of mesosomal membrane fractions from Micrococcus lysodeikticus

1. A method is described for the isolation of pure mesosomal membrane fractions from Micrococcus lysodeikticus. 2. Plasmolysis of cells, before wall digestion, was necessary for effective mesosome release. 3. The effect of mild shearing forces, temperature and time upon the release of mesosomal membrane from protoplasts was investigated. 4. The optimum yield of mesosomal membranes from stable protoplasts was achieved at 10mm-Mg(2+). 5. Mesosomal membrane vesicle fractions prepared at differing Mg(2+) concentrations above 10mm were similar in chemical composition. 6. Comparison of the properties of peripheral and mesosomal membrane fractions revealed major differences in the distribution of protein components, membrane phosphorus, mannose and dehydrogenase activities between the two fractions. 7. Only cytochrome b(556) was detected in mesosomal membranes, whereas peripheral membranes contained a full complement of cytochromes. 8. Preliminary investigations suggested the localization of an autolytic enzyme(s) in the mesosomal vesicles. 9. The anatomy of mesosomal and peripheral membrane have been compared by the negative-staining and freeze-fracture technique. 10. The results are discussed in relation to a plausible role for the mesosome.