Azospirillum brasilense was treated with nitrosoguanidine and five machete resistant mutant strains were isolated. The effect of machete on growth, N2-fixation, cell constituents, hydrogenase activity, nitrogenase activity, glutamine synthetase, and nitrate reductase activities were studied. Mutant strains MHT 3 and MHT 5 showed lesser nitrate uptake and exhibited greater growth, hydrogenase activity (H2 uptake), G.S. activity, and N2ase activity in nitrogen free medium than parental and other mutant strains at 30°C compared with 42°C. Inoculation of rice with A. brasilense and mutant strains led to a significant increase in nitrogenase activity and grain yield compared with the uninoculated control with and without machete (handweeded). Differential response of strains was noted on the nitrogen contents of plants and seeds with significant strains × genotype interaction. These mutants were stable and retained their resistance even after several subcultures through medium free of machete.
The occurrence of vast amounts of streamers was observed widely in acid mine drainage water from the abandoned Matsuo sulfur and iron sulfide mine area. The acid streamers were commonly white or cream colored and gelatinous, and were composed of many fine fibers. The streamers showed strong oxidizing activity of ferrous iron, sulfur and thiosulfate in an inorganic acid environment. Microscopic examinations of the streamers indicated that morphologically-similar bacterial rods multiplied in a long oriented cell chain and that a great number of the bacterial cell chains were combined in a zoogleal big conglomeration. The acid streamers were a mass of acidophilic, obligately chemolithotrophic iron-oxidizing bacteria, proved to be Thiobacillus ferrooxidans, which were embedded in a gelatinous matrix.
The effects of the concentration of the medium components and other cultural conditions on the total cell number and on the lipid content (mg of total lipid/108 cells) of the fat yeast Lipomyces starkeyi were examined. The no addition and deficiency of NH4+, K+, Mg2+, PO43-, SO42-, Zn2+, Fe3+, or Mn2+ decreased the total cell number. Mn2+ sufficiency increased the total cell number by a factor of 1.5 to 1.7, as compared with that of the standard concentration. The lipid content of the yeast was affected by six (NH4+, K+, Ca2+, Zn2+, Fe3+, and Mn2+) ion concentrations. The no addition and deficiency of Zn2+ increased the lipid content by a factor ranging from 2.4 to 2.8 in comparison with that of the standard concentration. The concentration of Zn2+ also altered the lipid yield (g of lipid/100g of glucose consumed) considerably. The concentration of Na+, Cl-, Cu2+, BO33-, I-, MoO42-, and biotin had almost no effect on the total cell number, lipid content, and lipid yield of L. starkeyi. The cultural temperature and the initial pH value of the medium affected the total cell number and lipid content; the optimum temperature ranged from 25.5 to 29.5°C, and the optimum pH value was 4.9. A low concentration of dissolved oxygen decreased both the total cell number and lipid content. D-Glucose, D-mannose, D-galactose, D-levulose, sucrose, D-xylose, and L-arabinose proved to be usable carbon sources for the growth and the lipid accumulation of L. starkeyi.
Cd2+ uptake rates in the cyanobacterium Anacystis nidulans IU 625 (ATCC 27144) were found to be concentration-dependent. While Ca2+ and Zn2+ showed competitive inhibition, Hg2+ enhanced Cd2+ uptake. The pH values optimal for growth of the organism (pH 8.5) resulted in more Cd2+ uptake than low (pH 6.5) or high pH (10.0) conditions. Dithiol (dithiothreitol) proved more effective in lessening Cd2+ uptake than monothiol (mercaptoethanol). The test organism suspended in spent medium showed negligible Cd2+ uptake. Among the sythetic complexans, EDTA inhibited metal uptake, while citrate favored the process. There was more Cd2+ uptake by dense cultures, but the specific rate expressed per unit protein was less.
Taxonomic studies on Debaryomyces hansenii (ZOPF) Lodder et Kregervan Rij and related yeast species were carried out using chemotaxonomic methods including DNA base composition, DNA-DNA hybridization, ubiquinone system, proton magnetic resonance spectrum of mannan, and serological methods. The 50 strains employed were classified into 3 groups, I, II, and III, based on DNA-DNA hybridization experiments. These groups were considered to represent three distinct species. Group I consisted of two subgroups, Ia and Ib, which were considered to represent two distinct varieties. These groups were also characterized by proton magnetic resonance spectra of alkali-extracted mannans and cell surface antigens, however, they could not be discriminated by DNA base composition and ubiquinone systems, in addition to the taxonomic criteria commonly employed in yeast taxonomy. Group Ia comprised 34 strains including the type or authentic strains of D. hansenii, D. nicotianae, D. nicotianae var. minor, D. kloeckeri, D. kloeckeri var. major, D. tyrocola, D. gruetzii, D. matruchoti, D. matruchoti var. cesarii, D. hildegaardi, D. guilliermondii, D. miso, Torulopsis westerdijkii, T. famata, and T. minor. Group Ib comprised 6 strains including the type or authentic strains Of D. subglobosus, D. fukuyamaensis, Pichia adzetii, and Candida flareri. Group II comprised 4 strains including the type or authentic strains of D. nepalensis, D. cavensis, and D. japonicus. Group III comprised 6 strains including the type strain of T. candida.
Comparative taxonomic studies were carried out on strains of groups I, II and III, and subgroups Ia and Ib of Debaryomyces hansenii and related species which were found in the preceding paper on the basis of chemotaxonomic investigations, for the practical discrimination and clarification of nomenclature. These groups and subgroups could be discriminated from one another by maximum growth temperature, assimilability of propylene glycol, and electrophoretic patterns of glucose-6-phosphate dehydrogenase (G6PDH, EC 126.96.36.199) and malate dehydrogenase (MDH, EC 188.8.131.52), in addition to the criteria reported in the preceding paper. Strains of group III (Candida saitoana nov. nom.) could be easily discriminated from strains of other groups by their ability to assimilate propylene glycol and electrophoretic relative mobilities of G6PDH and MDH, in addition to their characteristic patterns of PMR spectra of mannans and cell surface antigens. Strains of subgroup Ia (Debaryomyceshansenii var. hansenii-Candida famata var. famata) could be discriminated by their low maximum growth temperature and the lack of G6PDH activity. Discrimination of strains of subgroup Ib (Debaryomyceshansenii var. fabryi nov. comb.-Candida famata var. flareri nov. comb.) from those of group II (Debaryomyces nepalensis-Candida naganishii nov. sp.) is not so easy in the present study. At present, electrophoretic comparison of MDH is the most convenient method for the separation of group II and subgroup Ib from each other because the differences found in the patterns of PMR spectra of mannans and cell surface antigens are not so clear-cut in several strains.
A method enabling the analysis of the variation of cell length during the cell cycle of Schizosaccharomyces pombe using an asynchronous chemostat culture was developed. It was used to experimentally test the proposal that for the first 75% of the cell cycle the cell grows only in length and during the last 25% of the cell cycle there is no change in cell length. The results obtained question the validity of this proposal and are consistent with a control in which, as specific growth rate (or equivalently energy source availability) increases, a smaller portion of the cell cycle is required for the total length increase which occurs during the cell cycle. This is consistent with "critical mass" theories for the initiation of various cellular events which would be expected to be initiated at an earlier stage of the cell cycle in the case of rapid growth.
Two expression vectors, pEBR-15 and pEBT-5, were constructed using the PR promoter of coliphage λ and tac promoter, respectively. Structure gene of Bacillus subtilis early sporulation gene spoOF, having its own ribosome binding site but no promoter, was inserted at the downstream region of the PR promoter or tac promoter. Expression of the spoOF gene in Escherichia coli is controlled under the PR promoter or tac promoter of the vector. After induction, a protein of 21K dalton is overproduced to about 12% of the total cellular proteins under control of the PR promoter, or about 4% under control of the tac promoter. The 21K protein was purified to 99% purity by two steps of column chromatography. Comparison of the purified 21K protein with the spoOF gene product synthesized in B. subtilis minicells by two-dimensional gel electrophoresis and the analysis of the NH2-terminal amino acid sequence of the purified 21K protein revealed that the 21K protein is the spoOF gene product.
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Edited and published by : Applied Microbiology, Molecular and Cellular Biosciences Research Foundation/Center for Academic Publications Japan Produced and listed by : TERRAPUB, Center for Academic Publications Japan/Shobi Printing Co., Ltd. (-Vol.60,No12), Center for Academic Publications Japan/InternationalAcademic Printing Co., Ltd.(-Vol.54,No1)