DNA-synthesizing activity of a mutable strain, MU-10, selected from the phleomycin-resistant mutants was investigated in comparison with that of parental strain, 160 trp. The DNA-synthesizing machinery in MU-10 was more sensitive to high temperature and more resistant to phleomycin than that in 60 trp and, moreover, the mutant did not allow the full synthesis of phage DNA although the cell took up the phage genome. The mutator gene, mut, was unseparable by genetic means from the phleomycin-resistant gene (phl).
A genetic character of a pyocinogenic factor responsible for the production of pyocin R3 of Pseudomonas aeruginosa was studied. This factor could be transferred from the original strain PAT to PAO strains by FP2-mediated conjugation or by transduction with a bacteriophage. The behavior of pyocin R3 factor was compared with that of pyocin R2 factor. The results indicated both pyocinogenic factors to be linked to a certain tryptophan marker. The exchange of pyocin factors was observed when the pyocin R3 factor was introduced into pyocin R2-positive recipients. It is concluded that pyocin R3 factor is integrated into the bacterial chromosome at a corresponding position of pyocin R2, close to trp-1-str region.
The genetic factor responsible for the production of pyocin R1 was found to be transferable from the original strain P15 to PAO sublines by F116 transduction. Similar to pyocin R2 and R3 factors, R1 factor was cotransduced with trp-1 marker. The behavior of the R1 factor was studied in PAO comparing with other pyocin factors. The results suggest that all these pyocin factors occupy a similar position close to trp-1 in the chromosome of PAO strains.
The characteristics of the pH-dependent biotin requirement of Lipomycesstarkeyi IAM 4753 were investigated in growing cells. Microbiological and radioisotope assays were employed to measure biotin content in the cells and in the medium. This yeast exhibited a strict biotin requirement in a medium with a pH ranging from 5.5 to 6.5. The minimum amount of biotin needed for normal growth in the bufferized medium with a pH of 6.0 was 0.1μg/liter. The maximum growth rate was observed when 0.5μg or more of biotin was added to the bufferized medium with a pH of 6.0; cellular radioactivity increased gradually accompanied by an increase of true biotin in the cells until the concentration of true biotin in the medium became undetectable. A part of the biotin added was degraded during the growth. Cellular biotin content remained constant for about 10hr followed by a gradual increase. The reincrease of the cellular true biotin content began at a point when the pH of the medium was below 5.5. From these results, it was concluded that the initiation of biotin biosynthesis in L. starkeyi IAM 4753 depends on the pH value of the medium.
Ecological survey of yeasts was conducted during the cruise of KH-67-5, by the research vessel Hakuho-Maru of Ocean Research Institute, University of Tokyo, along Long. 150°E from Lat. 44°N to the equator in the Pacific Ocean in December, 1967. Yeasts were detected from the surface to a depth of 4, 000m. Of 184 seawater samples, 27.7% were positive for yeasts. The average number of yeasts detected in 1 liter of seawater was 56.7 for yeast-positive samples and 15.7 for total samples. Isolated yeast strains were identified as strains belonging to the genera of Rhodotorula, Cryptococcus, Debaryomyces, and Candida. The effects of salt concentration, temperature, pH, and hydrostatic pressure on the growth of selected strains were studied for the assessment of the possibility whether the reproduction of marine-occurring yeasts is actual or not in the environment in situ. Maximum NaCl tolerance ranged from 9 to 21%, exhibiting fairly good growth at NaCl concentration of seawater. The pH threshold for growth on alkaline range overlapped with the pH range of seawater. The pH 8.1, a widely observed pH in the sea, was deleterious for most of the strains. It was suggested that marine yeasts may be subjected to extensive pH effects by different bodies of seawater. The maximum tolerance to increased hydrostatic pressure observed among the strains was 400 to 500 atm, which corresponds to a depth of 4, 000 to 5, 000m. It was suggested from the pressure experiments that for the growth of most marine yeasts hydrostatic pressure is not so exacting until the depth reaches 2, 000m, and its adverse effect increases with depth and are remarkable at the depth of 4, 000m or more. Though marine-occurring yeasts seemed to be more tolerant to hydrostatic pressure than terrestrial yeasts, no clear relationship could be found between the tolerance and the depth from which they were isolated.
Identification studies were made on yeast cultures isolated from sea water samples collected from 0 to 4000m depth in the Pacific Ocean. Twenty strains were identified as strains belonging to the following seven species of four genera: Three strains of Debaryomyces hansenii, one of Cryptococcus albidus var. albidus, two of Candida diddensii, one of C. krissii nov. sp., five of Rhodotorula glutinis var. glutinis, five of Rh. rubra, and three of Rh. marina. Description and Latin diagnosis of C. krissii nov. sp. are given.
Seven marine yeasts were isolated from seawater (from 0.3 and 2.0m depth) and sediment samples (from 5.5m depth) in Aburatsubo Inlet of the Miura Peninsula, Japan. These yeasts were identified as Debaryomyceshansenii (two strains), Torulopsis candida (two strains), Rhodotorularubra, Rh. marina, and Cryptococcus infirmo-miniatus.