The growing cells of Clostridium species were lysed by the addition of univalent cations such as Na+, K+, Rb+, Cs+, Li+, and NH4+ In various kinds of bacteria tested, strains of Cl. Saccharoperbutylacetonicum were the most sensitive to Na+ The lysis occurred at about 5min after addition of Na+, and completed at 20min or more. Most rapid lysis took place when the cells were during or toward the middle of the exponential phase of growth and when 0.3M Na+ was used. The presence of a low concentration of chelating agents such as EDTA and sodium citrate removed the 5-min lag period, and enhanced the rate of lysis. On the other hand, bivalent cations such as Ca2+, Mg2+, Ba2+, Co2+, Ni2+, and Zn2+ protected the cells from the lysing action of Na+. In addition, these phenomena could be applied for the isolation of bacterial DNA and for the estimation of intracellular development of bacteriocin, since Cl. Saccharoperbutylacetonicum was not lysed by lysozyme and was considerably resistant to chloroform.
Studies were made on the characteristics of guanosine-producing mutants of a Bacillus strain, GnR-44 and GnR-176, which were assumed to be deficient in purine nucleoside-hydrolyzing activity. In a culture with GnR-44, guanosine accumulated from an initial stage and increased with culture time, while with the parental strain purine bases accumulated at first, followed by the corresponding nucleosides. From experiments with a cell-free extract, these mutants were considered to be partially deficient in the phosphorylase activity for inosine, guanosine, and xanthosine. In replacement culture with GnR-44, inosine added to the medium was converted into xanthosine and guanosine, while xanthosine and guanosine appeared to remain unchanged when they were added. From these results, it was presumed that "partially defective" purine nucleoside phosphorylase of the mutants played an important role in the accumulation of guanosine.
Frequency of the appearance of phage A-1-resistant mutants of Bacillussubtilis, an inosine producer, was higher on synthetic media than on natural media. The character of phage resistance in most of the mutants, however, was very unstable and the mutants became sensitive during preservation on the same medium on which they had been isolated. Since A-1-resistant mutants grew slowly on any media used compared to the parental sensitive strain, this type of conversion could be explained by "population change" caused by the increase of phage-sensitive revertant cells during cultivation or successive transfers. To prevent this conversion, the presence of phage A-1 was utilized for eliminating the sensitive cells during the maintenance of resistant strains. Another type of conversion was observed when phage-resistant mutants obtained on a natural medium were transferred to some synthetic media and vice versa. Several saccharides, such as glucose, glucosamine, and ribose, were found to stimulate the conversion when resistant cells were transferred from natural medium to synthetic medium. This conversion was prevented by the isolation of phage-resistant mutants successively on various media.
The increase in the length of the major axis of daughter cells as a measure of cell growth was re-examined with special reference to the nuclear behavior, employing a diploid strain of Saccharomyces cerevisiae. The increase in cell size in a cell cycle proceeded in a similar manner either in the synchronous culture or in the single-cell culture as a number of investigators described. Newly established facts concerning the size of daughter cells in a growth process are as follows: The newborn daughter cells had a rather uniform size under definite conditions regardless of the size of their mother cells. The heterogeneity in the cell size was mainly due to its divisional age; the cell increased in size with every budding, and the difference in cell size between age 0 and age 1 was the most prominent. The newborn daughter cells initiated budding some time after the mother cell had initiated budding, during which time the size of daughter cells generally increased. Shape of the bud varied gradually during the growth process. The bud- initial was cylindrical and then gradually became the prolate spheroidal form. Nuclear events such as DNA synthesis and nuclear migration proceeded also in a similar manner as others described. The daughter cells exhibiting migrating nucleus in the Giemsa-stained preparations showed extraordinary uniformity in size distribution. This shows that the migration of nucleus is a very rapid process; it may proceed within a period of 0.1 generation and the cell size at the time of nuclear migration was estimated to be about the fraction of 0.8 of its full size.
Various factors influencing the life of rumen protozoa, Entodinium species, were studied. Optimal conditions for entodinial survival were determined for the following factors: Temperature, 38-40°; pH, 6.0-7.0; redox potential, -250 to -400mV; osmotic pressure, 0.7-1.0% NaCl equivalent. The influence of various compounds formed by rumen microorganisms was examined and toxic levels were found; ammonia had a harmful effect on the protozoa above the level of 3mmol/100ml; methylamine, histamine, and formate above 10mmol/100ml; methanol and ethanol above 30mmol/100ml. Acetate, propionate, butyrate, and lactate had no deleterious effect within the limits tested. In addition, the influence of antibiotics is described.