The lethal effect of cold shock to a thymine-requiring Escherichia coli was investigated with special reference to the nature of DNA after the cold shock. The cells were labeled with 3H-thymine during growth. Labeled cells were cold-shocked and lysozyme-lysates prepared. The depolymerization of DNA by endogenous nucleases was faster with the lysate prepared from cold-shocked cells than those from unshocked control and magnesium-recovered cells. The result indicates that cold-shocked cells contain DNA which is more susceptible to endogenous nucleases than DNA in unshocked or recovered cells. The lysates from cold-shocked, unshocked, and recovered cells were heat-treated and quenched rapidly at high salt concentrations. The resulting single-strand DNA was adsorbed by nitrocellulose. It was found that DNA of cold-shocked cells contain more single-strand breaks (nicks) than the unshocked or recovered cells. These results provide an evidence for the involvement of DNA-ligase reaction in the process of recovery from the cold shock. Possible mechanism of the lethal effect of cold shock is discussed.
Glyceryl ether containing phospholipid was found to exist in a strictly anaerobic bacterium, Selenomonas ruminantium. Glyceryl ether fraction was obtained from total phospholipid by LiA1H4 and methanol-HCl treatments followed by column chromatography with silicic acid. Glyceryl ether was identified by thin-layer chromatography and infrared absorption spectrum. The molar percentage composition of glyceryl ether in total phospholipids was approximately 3. When labeled valerate or caproate was supplemented to a glucose medium, the radioactivity was incorporated into fatty alcohols of glyceryl ether side chains. The major radioactive components of glyceryl ether from 14C-valerate grown cells were C11:1, C9:0, and C13 fatty alcohols. When cells were grown with 14C-caproate, the major radioactive glyceryl ether contained C12:0, C12:1, and C10:0 fatty alcohols.
Control of respiration similar to that seen in mitochondria of higher plants and animals was found in the phosphate-deficient cells of Brevibacteriumammoniagenes when phosphate is supplied, and was named "Pi-effect." The phosphate-deficient cells of this organism can incorporate phosphate at a great rate whereas the phosphate-sufficient ones can take it up only slightly. Accompanying the phosphate incorporation, marked stimulation of the rate of respiration is observed and after exhaustion of phosphate the rate returns to the initial low level. This stimulation by phosphate can be repeated many times until cellular phosphate pool is filled to the maximum extent. The "Pi-effect" is independent of the phosphate transport as a counterion in cation transport, phosphate-requiring enzyme systems, substrate level phosphorylation in glycolytic pathway, and the energy-requiring synthesis of macromolecules. The "Pi-effect" is distributed widely in gram-negative enteric bacteria. The relationship between the "Pi-effect" and phosphorylating respiration in this organism is discussed.
Studies on the distribution of pigmented bacteria in ‘Usar’ (alkaline) soils indicated that their number is directly proportional to salinity, the light playing no obvious role. The results also suggest that the bacteria found in these soils are temperature sensitive and do not show any temperature-salinity relationship.
Glyceryl ether phospholipids were found to exist in various strictly anaerobic bacteria and propionibacteria. The strains included Selenomonasruminantium, Veillonella gazogenes, Propionibacterium freudenreichii, Propionibacteriumshermanii, Clostridium saccharoperbutylacetonicum, Clostridiumacetobutylicum, Clostridium perfrigens, and Clostridium kaneboi. Selenomonasruminantium contained the largest amount of glyceryl ether phospholipids among the tested bacteria. The molar percentage composition of glyceryl ethers in total phospholipids from Selenomonas ruminantium was approximately 3. Glyceryl ether phospholipid was not detected in aerobic and facultative anaerobic bacteria even when they were cultured under strictly anaerobic conditions.
By using the sporulation system of Bacillus megaterium, analysis of the protein-synthesizing system in sporulating cells was made. By comparing the content of amino acid composition in vegetative cells and spores, it was found that spores were richer in cysteine-cystine, aromatic acids, basic amino acids and serine. Glutamic acid was the major amino acid in the soluble pool but rapidly decreased during sporulation. Rate of incorporation of several amino acids into protein fraction was observed to change at the onset of sporulation. Inhibition experiments with chloramphenicol suggested that the cells exhibit a chloramphenicol-insensitive level of protein synthesis at all stages which differs during the different stages. This non-inhibitory level in sporulating cells may be the major protein synthesis for sporulation.