Growth of Arthrobacter simplex in its heat-killed cell suspension was studied. Growth yield increased in the culture supplemented with inorganic salt mixture. The effect was common to many inorganic salts including chlorides of alkaline and alkaline earth metals and ammonium. The optimum concentrations of inorganic salts were 0.5 to 1.0mM for chlorides of bivalent cations and 2.5 to 10mM for univalent cations. Inorganic salts were effective in the utilization of the compounds present in the insoluble part of the heat-killed cell suspension. Protein, amino acids, DNA, and RNA were utilized as growth substrates. When inorganic salt was not supplemented, growth was dependent mostly on the materials released from the cells by heating. The growth substrates were amino acids and a part of RNA. It was also observed that the larger the number of heat-killed cells supplied was, the higher was the ratio of viable cell number attained to that of heat-killed cells. This observation was explained in relation to the effect of inorganic salts on the growth. Possible mechanism of the stimulating effect of inorganic salts was discussed.
An actinomycete of the proposed name Nocardia pseudosporangifera n. sp. was isolated from the soil in the oil field using ethane-enrichment ulture. The new organism is characterized by the formation of spherical bodies resembling pseudosporangia of Actinosporangium Krassilnikov and conidia in the aerial mycelium. The organism utilizes propane and several hydrocarbons higher than undecane besides ethane and grows autotrophically on hydrogen.
Various enzymic transformation of progesterone with Rhizopus nigricans REF. 129 was studied by allowing the fermentation to proceed at different time intervals ranging from 2 to 192hr. The monohydroxylated compounds, 11α-, 17α-, and 21-hydroxyprogesterone, were formed at the early stage of fermentation. Later on, 11α-hydroxyallopregnane, followed by 6β, 11α, dihydroxyprogesterone, and then 11α, 17α-dihydroxy derivative and epicortisol were detected. Different derivatives of progesterone were used as substrates in a trial to investigate the pathways of progesterone transformation by the experimental organism. A scheme is put forward summarizing these reactions.
A strain of Staphylococcus aureus resistant to oxytetracycline and cross-resistant to tetracycline was isolated and the mechanism of its resistance to the drug was studied. 1. The incorporation of amino acids-U-14C into the protein fraction decreased in the sensitive cells upon addition of oxytetracycline (10μg/ml), while no remarkable influence was observed in the resistant cells. On the other hand, the incorporations of amino acids-U-14C into the protein fraction with the cell-free extracts from the sensitive as well as the resistant cells were equally inhibited by tetracycline. 2. The uptake of radioactive tetracycline by the sensitive cells was much higher than that by the resistant cells. In order to investigate the mechanism of the decrease in the permeability of the cells to the drug, the intracellular concentration of tetracycline was estimated from the uptake of the drug and its inhibitory effect on the protein biosynthesis in the intact cells. Permeability of the resistant cells to the drug was found to decrease to about 1/100 of that of the sensitive ones and a large part of the drug taken up by the resistant cells seemed to be non-specifically bound to the cellular surface. 3. At low concentrations of tetracycline, its uptake by the sensitive cells was decreased by lowering the temperature or by the addition of energy poisons such as azide, while the uptake by the resistant ones was not much affected. At high concentrations of tetracycline, on the other hand, its uptake by the resistant cells was inhibited by azide as in the sensitive cells.
Transformation of genetic traits by extracellular DNA was found in several mutants of Bacillus sublilis Marburg. The mutant strains acted as donors as well as recipients of transformation except for strain S8OTi which mainly acted as a donor. The donor activity of a strain was not correlated directly with its recipient activity. The cells released DNA most abundantly in the fast-growing phase and majority of the released DNA was found in the non-filtrable fraction. The DNA in the non-filtrable fraction yielded a large number of single and double transformants. Mechanism of this transformation by the non-filtrable DNA was discussed.
Cell wall polysaccharide content of small- and large-sized cells which were obtained by fractional centrifugation of commercial baker's yeast was determined. The small-sized cells contained significantly lower amount of glucan and higher amount of mannan than the large-sized cells. Glucan content of small cells obtained by the fractionation of laboratory-cultured cells was also lower than original cells, and increased by various treatments which make the cell size larger. Determination of cell wall polysaccharides during the course of synchronous proliferation of large cells revealed that mannan is synthesized linearly during cell division cycles, whereas glucan synthesis proceeded intermittently; that is, it was seen mainly in the latter half of the cell division cycle. The difference in cell wall polysaccharide content between the small and large cells might be explained from these results and the position of the small cells in the cell division cycle, which was discussed in the preceding paper.