Investigations were made on the dead cell formation in the growth of the baker's yeast in pantothenate deficiency and the concomitant occurrence of a variant strain which can grow better at lower concentrations of pantothenate. 1. The rate of dead cell formation varied with the kind of amino acids present in the medium at a certain concentration of pantothenate. Methionine and leucine were most effective in producing the dead cells even at a comparatively high concentration of pantothenate. At lower pantothenate concentrations, addition of various amino acids induced marked production. 2. The dead cells were produced even at an early stage of growth. 3. When the yeast cells were incubated for 2 or more days in a medium, possible in producing a large number of dead cells, a variant strain always appeared. The variant strain can grow better even at very low concentrations of pantothenate, but shows longer lag phase and slightly poorer growth than do the original one, when a sufficient amount of pantothenic acid was supplied. 4. According to electron microscopic observation, the walls of the dead cells produced in pantothenate deficiency were slightly thicker than those of pantothenate-sufficient cells.
The DNA-DNA hybridization was studied by the DNA-agar method using 32P-labelled DNA of Bacillus subtilis Marburg and unlabelled DNA of eighteen strains of Bacilli. DNA's of several strains of B. natto and B. megaterium made hybrids with DNA of B. subtilis and the extent of hybridization correlated well with the genetic relatedness that had been studied by the interspecific transformation and phage-susceptibility.
Candida rugosa JF 101 capable of growing in mineral salts with individual pure alkanes as a sole carbon source produced a series of acids from decane. They have been identified as decanoic, decanedioic, octanedioic, adipic, and succinic acids. The intermediate oxidation products of decane has been isolated by resting-cell experiment and identified as decyl alcohol and decyl aldehyde. The degradation pathway of decane is discussed.
Fresh and dry conidia of Aspergillus oryzae were examined for their longevity under various storage conditions by testing germination rate at intervals over a year. Powdery conidia were stable for years when they were kept dry at 4°. Conidia stored in moist air (more than 70% relative humidity) survived for a few months, while those stored in moist nitrogen gas for less than a week. Washed conidia stored in water by shaking survived a little longer than powdery conidia stored in moist air. Characteristic difference between the storage of conidia in water and in moist air was that in the former case, but not in the latter, an acceleration of germination was observed at the initial phase of storage. The acceleration seemed to be caused by the fact that germination reaction proceeds partially even in water as demonstrated by 14CO2-incorporation into biopolymers. Deterioration of conidia appeared to be partially dependent on the consumption of mannitol, an intracellular storage substance. Modes of deterioration processes under different storage conditions were discussed based on the observations on respiratory and biosynthetic activities of conidia.
The development of the infection thread formed in the root hair of white clover (Trifolium repens L.) infected with Rhizobium trifolii was observed by electron microscopy on ultrathin sections of the infected root hairs. Development of the infection thread originates from a curled tip of root hair. The thread appears to be formed by the invagination of the surface structure of root hair into the cytoplasm, resulting in the formation of a tubular structure characterized by a wall (sheath) in the inside and cytoplasmic organelles on the outside. In this case major part of the root hair is vacuolized. A number of bacteroids are also seen in the sheath. When they are present in root hair, any observable membrane structure cannot be recognized. As the infection thread extends into the epidermal tissue of the root, the bacteroids are demarcated with irregularly shaped membrane, and in a rudimentary root nodule they become ovoid being demarcated with cell membrane but not with cell wall.
Effects of actinomycin-D on protein synthesis, RNA synthesis, and on formations of amylase, protease, alkaline phosphatase, and ribonuclease in Bacillus subtilis K were investigated. The RNA synthesis and the protein synthesis were inhibited quite similarly by actinomycin-D of various concentrations. Inhibition of the formation of amylase, protease, and alkaline phosphatase was also similar, but ribonuclease formation was quite resistant and was stimulated markedly at a lower concentration of actinomycin-D.
Two active components of the yeast invertase, designated as S-I and S-II, were highly purified and compared with each other with respect to the inhibition and activation characteristics, ultraviolet absorption spectrum and thermostability. These two enzymes were different in the following points: 1) The S-II enzyme is more sensitive to heavy metal ions, especially to Ag+ and Hg2+, than the S-I; the S-II activity is inhibited significantly by these two metal ions in concentrations of 10-6-10-7M, while no measurable inhibition of the S-I was demonstrated. 2) The S-I and S-II enzymes form stable derivatives of iodine, which ratained approximately 40 and 10% of activities of their native forms, respectively. 3) Cysteine activates the S-II enzyme to a larger extent but does not restore the activity of the iodinated S-II, while it reactivates the S-I enzyme. 4) With the S-II enzyme a larger increase in the absorbancy at 294mμ by basification was demonstrated than with the S-I enzyme, and the former is much more heat labile at the alkaline pH ranges than the latter. On the basis of these results the possibility of difference in the molecular configuration between these two enzymes has been discussed.
The action of polymyxin on El Tor vibrios was studied by following the growth pattern of the vibrios in polymyxin-containings media under various conditions. The results suggest that the antibiotic gets adsorbed on the cell surface whereafter its activity is determined by the metabolic state of the El Tor cells. The resting cells proved to be sensitive, a 24-hr old culture showed an initial period of inhibition followed by normal growth and a 2-hr old culture continued to grow normally in presence of the antibiotic. The degree of sensitivity appeared to be dependent also on the proportion between the number of cells and the concentration of polymyxin. It is suggested that an intracellular metabolic process which inactivates the polymyxin after its adsorption on the cell surface may be responsible for the resistance to the antibiotic shown by growing El Tor cells.