Mutants sensitive to fairly low concentration of threonine or methionine were derived from Brevibacterium flavum No. 2247 (ATCC 14067). These mutants were classified into three by the growth inhibition by threonine or methionine; type A was inhibited only by threonine, type B only by methionine, and type C by both threonine and methionine. Further, every type of mutants was divided into two subtypes by their growth response; one whose growth was inhibited by threonine (or methionine) was to be recovered in the coexistence of methionine (or threonine), and the other could not be recovered. Among these six types of mutants, one whose growth was inhibited by either methionine or threonine but could be recovered by threonine or methionine, respectively, was found to produce much lysine. This character is similar to that of the threonine-sensitive and methionine-sensitive revertant derived from a homoserine auxotroph lacking homoserine dehydrogenase activity. Homoserine dehydrogenase level of these revertants and the above-mentioned lysine-producing mutants were similar, being about 3% of the original strain, No. 2247, but a little difference was observed in the minimal inhibiting concentration of threonine or methionine and the kind of agents diminishing the inhibition by threonine or methionine. Furthermore, about one-half of threonine auxotrophs which were derived from the above-mentioned lysine-producing mutants sensitive to either threonine or methionine were found to produce larger amounts of lysine than the above parental mutants. A modified microbiological assay procedure using lysine auxotroph was introduced to isolate non-auxotrophic lysine-producing mutants directly from No. 2247. However, no mutants other than the two known types of lysine- producer (threonine- sensitive, methionine-sensitive mutants and S-(2-aminoethyl)- L-cysteine-resistant mutants) were found through this procedure.
The inorganic pyrophosphatase from Polyporus circinatus was partially purified. The enzyme was active at PH 7.0 and 8.4. Optimal conditions for hydrolysis of pyrophosphate was observed at 52°. The enzyme was specific for inorganic pyrophosphate and was dependent on Mg2+. The Michaelis-Menten constant was 5.0×10-4M at 37° and 5.5×10-4M at 52°.
DNA base composition (GC content) of 20 strains of Cryptococcus and 38 strains of Rhodotorula was investigated. Cryptococci employed exhibited the GC content of 49.0-59.5%, and were divided into 2 groups on the basis of their GC content as shown by Storck et al. The first group showed GC content of 58.8-59.5%, and comprised 5 strains representing 3 species. The second group exhibited GC content of 49.0-54.9%, and comprised 15 strains belonging to 10 taxa. The members of Rhodotorula showed the GC content of 50.0-68.5%, and were divided into 4 groups. The first group showed GC content of 66.8-68.5%, and consisted of 7 strains belonging to R. infirmominiata and R. glutinis. The second group showed GC content of 60.0-61.2%, and comprised 18 strains belonging to R. glutinis, R. glutinis var. dairenensis, R. glutinis var. rufusa, R. rubra, and R. pilimanae. The third group showed the GC content of 55.4-58.8%, and comprised 3 strains belonging to R. crocea, R. glutinis var. aurantiaca, and R. lactosa. The last group showed the GC content of 50.0-51.0%, and comprised 9 strains belonging to R. lactosa, R. pallida, R. minuta, R. marina, R. slooffii, R. zsoltii, and R. texensis. This grouping based on GC content agreed fairly well with that of Hasegawa based on requirement of specific vitamin, iodine reaction of culture broth, assimilability of lactose, optimum temperature for growth, and antigenic structure. Large intraspecific variations of GC content found in C. luteolus, C. laurentii, R. glutinis, and R. lactosa suggested the inadequateness of criteria presently employed in the classification of Rhodotorula and Cryptococcus.
A glucose-limited and an oxygen-limited chemostat cultivations of Azotobactervinelandii were carried out to secure the cells, different in the spectrum of the electron transport system relevant to respiration. Cellular contents of cytochromes c (c4+c5) and b1 decreased monotonously with the increase in dissolved oxygen concentration to an extent of 40× 10-6M in the chemostat cultures and then, leveled off. The maximum values of the content which appeared in a specific run of the oxygen- limited chemostat were two to three times those observed in the leveled-off region. Other cellular contents of cytochrome a2 and flavoprotein, however, were insensitive to the whole range of dissolved oxygen concentration (= 2.2 to 180×10-6M) in both types of the chemostat culture. Respiration rate of the bacterial cells thus harvested was measured by the exhaustion method; Km values in the Michaelis-Menten equation were not definite; the value of Km (=17×10-6M) with respect to the cells sampled from a specific chemostat with an extremely low level of dissolved oxygen (=2.2×10-6M) became larger with release from the stringent oxygen-limited condition in the chemostat cultures and approached infinite when the limiting factor of oxygen was replaced completely by glucose, i.e., dissolved oxygen became sufficient, in the original cultures. An intracellular spectrum of electron carrier, high energy metabolite, and dissolved oxygen, all participating in the enzymic reaction of cytochrome oxidase, were incorporated into the reaction model to elaborate on the respiration rate which was highly affected by the culture "career" of the bacterial cells.
As a result of studies on mycogenous fungi of mushrooms, mainly in two forests located in northern and central Japan, a total of 17 species representing 15 genera of Ascomycetes and Hyphomycetes are reported. Cephalotheca splendens is described as a new Ascomycete, distinct from the previously known species of the genus in its yellowish mycelial felt on which shiny black cleistothecia are borne and olive brown, discoid ascospores, measuring 3- 4×2.5-3.5×2-2.5μ. Included in the report are 5 imperfect fungi new to Japan, and several additional isolates.
The DNA base composition (GC content) of 44 strains of Torulopsis and related yeasts which represented 33 species and 2 varieties was studied. The GC contents of these yeasts ranged from 32.4 to 60.0%. Intrageneric variation was about 28%. The GC content was distributed rather continuously from low to high values and no prominent groups were detected on this basis. The wide range of Intrageneric variation and the pattern of distribution of the GC content indicated the heterogeneity and complexity of this genus. Urease-positive species were classified into 2 groups. One had relatively high GC content and was assumed to be related to heterobasidiomycetes, and the other had relatively low GC content and was assumed to be related to Schizosaccharomyces, though these two groups were not clearly discriminated only on the basis of their GC content.