Tricarboxylic acid transport-negative mutants of Salmonella typhimurium were isolated and partially characterized. It was found that S. typhimurium possesses another transport system in addition to the three systems described previously. The fourth system was induced by citrate and carried citric acid.
A thermosensitive mutant of Escherichia coli (E. coli strain ts612) was isolated by the transduction of polA+ as a selective marker with phage Plc which had been mutagenized with hydroxylamine. The mutation was mapped between ilv (74.7min) and metE (75.5min). When the incubation temperature of this mutant was shifted from 30° to 42°, the cell division was interrupted immediately after the shift of temperature, although the optical density at 660nm of the culture continued to increase for 90min. The mutant did not support the multiplications of phages T4 and lambda at 42°, while it allowed the growth of phage T7. Electrophoretic analysis of membrane proteins of the mutant suggested that a part of the membrane protein was diminished when the mutant was incubated at the restrictive temperature.
The activities of enzymes in the Krebs cycle and in electron transport were determined with membrane and soluble fractions of Escherichiacoil cells grown aerobically or anaerobically with or without glucose. The absence of oxygen during growth decreased the levels of aconitate hydratase, isocitrate lyase, isocitrate dehydrogenase, fumarate hydratase, NADP-malate dehydrogenase, NADH-oxidase, and cytochrome b1, while the presence of glucose repressed the levels of aconitate hydratase, isocitrate lyase, fumarate hydratase, and succinate dehydrogenase. Formate dehydrogenase was repressed only when cells were grown anaerobically with glucose, while NADPH-oxidase and menadione reductase were neither repressed by glucose nor by anaerobiosis. Regardless of the cultural conditions, most of the activities of formate dehydrogenase, succinate dehydrogenase, NADH oxidase, and cytochrome b1 were found in the membrane fraction, but the proportions of the activities found in soluble fraction considerably increased when the formation of these enzymes was repressed by anaerobiosis or by glucose.
An isolation method and some analytical results of intracellular oil globules of the yeast Lipomyces starkeyi are described. Protoplasts, prepared by digestion of the cells with snail gut juice, were lysed by hypotonic osmotic shock. The oil globules in the lysate were separated by repeated centrifugations and floatations through discontinuous sucrose buffer solutions. Scanning electron microscopic observations revealed the presence of membranous outer surface on the oil globules. Oil globules contained triglyceride as a major component which represented about 85% of the lipid carbon. Oil globules were found to contain polar lipids and protein as minor components. Analytical data on the polar lipids by thin-layer chromatography showed the main polar lipid to be phosphatidylethanolamine which represented over 95% of the polar lipid carbon. The presence of phosphatidylcholine, phosphatidylserine, and/or phosphatidylinositol, which are important constituents in the whole cells of L. starkeyi, was detected but they were minor constituents.
The extraction of lipopolysaccharides (LPS) from Escherichia coli 6234 was studied. It was found that approximately one-half of LPS was extracted with cold phenol-water without stirring (4-LPS). The remaining LPS was extracted with hot phenol-water with stirring (470-LPS). When the cells were extracted directly with hot phenol-water, all LPS was extracted in the aqueous layer (70-LPS). The three preparations were partially purified and their chemical compositions were examined. Marked differences in the chemical compositions were observed between the 4-LPS and 470- or 70-LPS. The 4-LPS was rich in fatty acids and hexosamine in lipid A moiety. The 470- and 70-LPSs showed similar chemical compositions. When the 4-LPS was treated with hot phenol-water, a partial degradation of the lipid A moiety was observed. These results were discussed with respect to the native state of LPS in the outer membrane of the envelope.
Effect of Mitomycin C treatment on the host cell capacity for multiplication of φA was investigated, taking advantage of Ca2+-dependent transfection of the replicative-form DNA. In contrast to uvr+, uvrD, and uvrF strains, cells of uvrA, uvrB, or uvrC mutant sufficiently supported the viral multiplication after treatment with 50μg/ml of Mitomycin C. The host capacity of uvrE strain showed an intermediate sensitivity to Mitomycin C. Plaque yield of φA in rec- strains was, as in rec+uvr+ hosts, markedly decreased by pretreatment with Mitomycin C. In contrast with DNA polymerase II, both polymerizing activity and 5′-3′ exonuclease activity of DNA polymerase I were involved in host-cell reactivation for ultraviolet-irradiated replicative form. The capacity to develop φA of polA, polA 107, and resA mutants was, like that of pol+ or polB1 strains, conspicuously decreased upon treatment with the antibiotic. Effect of several radiomimetic agents on the host capacity was compared with that of Mitomycin C. In ultraviolet sensitivity of the host capacity, a small difference was observed between uvr+ bacteria and uvrA mutant. Infectivity yield of Mitomycin C-treated replicative-form was not particularly affected by uvrA mutation.