Isao Yumoto

Isolation of clustered genes that are notably homologous to the eicosapentaenoic acid biosynthesis gene cluster from the docosahexaenoic acid-producing bacterium Vibrio marinus strain MP-1

A 40-kbp DNA fragment was isolated from the cosmid library of Vibrio marinus strain MP-1. Among the 22 putative open reading frames (ORFs) in this fragment, ORFs 8, 9, 10 and 11 had high homology with ORFs 5, 6, 7 and 8 of the eicosapentaenoic acid biosynthesis gene cluster, respectively. Then, we speculate that these ORFs are responsible for docosahexaenoic acid biosynthesis in this bacterium.

Isolation of a Pseudomonas species from fish intestine that produces a protease active at low temperature

A psychrotrophic bacterium producing a protease active at low temperatures was isolated from fish intestine and identified as a Pseudomonas species. Optimum growth and protease‐producing temperatures of this strain were 15°C and 10°C, respectively. The maximum temperature for proteolytic activity was 25°C, an unusually low temperature.

Direct fermentation of starch to L-(+)-lactic acid using Lactobacillus amylophilus

SummaryFermentation of L-(+)-lactic acid from soluble starch by Lactobacillus amylophilus was studied. The bacterium produced about 30 g of L-(+)-lactic acid from 50 g of soluble starch when the pH of the culture was ranging from pH 5 to pH 6.8 at 28°C. 53.4 g of L-(+)-lactic acid was produced when 100 g of starch was added in the medium. The fermentation procedures will reduce the cost of complete hydrolysis of starch to glucose prior to fermentation.

Identification of facultatively alkaliphilic Bacillus sp. strain YN-2000 and its fatty acid composition and cell-surface aspects depending on culture pH.

Abstract Facultatively alkaliphilic Bacillus sp. strain YN-2000 was isolated from an indigo ball. Although the strain has been extensively investigated as a representative strain of alkaliphilic bacillus, its taxonomic position is not yet known. Morphological, biochemical, and physiological characteristics and chemotaxonomic properties indicated that the strain was closely related to Bacillus cohnii; this was confirmed by the high homology of the 16S rRNA sequence and the construction of a phylogenetic tree on the basis of the 16S rRNA sequence and DNA–DNA relatedness data. Strain YN-2000 contained a larger amount of unsaturated fatty acids compared with Bacillus subtilis and the obligate alkaliphile, Bacillus alcalophilus, regardless of its culture pH. When the cells were grown at pH 10, the unsaturated fatty acid content and anteiso-/iso-branched fatty acid ratio became lower than those at pH 7. This result suggests that membrane fluidity decreases when the cells are grown at pH 10 compared to those of pH 7. In the cells of strain YN-2000 grown at pH 10, the cell-surface aspect was rougher, the cell shape was longer, and the cell-surface layer was thicker compared with those of the cells grown at pH 7. The cell-surface structural change might be related to adaptation to an alkaline environment.

Isolation of Vibrio sp. S-1 exhibiting extraordinarily high catalase activity

Abstract A bacterium exhibiting extraordinarily high catalase activity was isolated from a drain pool of a fish product processing plant that uses H2O2 as a bleaching and microbicidal agent. The isolate was a gram-negative, rod-shaped, oxidase-positive, facultative anaerobe capable of both fermentative and respiratory metabolism, and sensitive to vibriostatic compound O 129 . Although the isolate was non-flagellated, its taxonomic characteristics and phylogenetic position based on a 16S rRNA analysis indicated that it belonged to the genus Vibrio. A culture medium containing living cells and a cell-free extract prepared from 48-h cultured cells of the isolate exhibited catalase activity of 680 units/mg cells and 7276 units/mg protein, respectively. The activity of the cell-free extract of the isolate was 2 orders greater than those of Escherichia coli and Bacillus subtilis. Application of the newly isolated bacterium or its enzyme will provide an effective means of decomposing H2O2 contained in industrial waste such as that produced in the paper, food, textile, and semiconductor industries.

Comparative study on cytochrome content of alkaliphilic Bacillus strains

Abstract The cytochrome content was estimated in a wide range of alkaliphilic Bacillus strains with DNA G + C contents from 34.4 to 44.3%. Among the strains tested, four facultative alkaliphiles, whose G + C contents were around 36%, and one obligate alkaliphile, with a G + C content of 41.4%, possessed relatively high amounts of total cytochrome (more than 0.3 nmol · mg cells −1 ). These five alkaliphiles contained high amounts of cytochromes b and c compared with the other strains tested, but their cytochrome a contents were not noticeably different. All the tested alkaliphilic strains had much higher amounts of cytochrome than B. subtilis (neutrophile), except for two facultative alkaliphiles with G + C contents around 40%. These results suggest that various bioenergetic strategies are used by alkaliphilic Bacillus for adaptation to a high alkaline environment, and that cytochromes b and c have a bioenergetically very important role in certain kinds of alkaliphiles.

Gene cloning and expression of the catalase from the hydrogen peroxide-resistant bacterium Vibrio rumoiensis S-1 and its subcellular localization

The catalase gene, vktA, of the hydrogen peroxide-resistant bacterium Vibrio rumoiensis S-1 has been isolated and sequenced. Plasmid pBSsa1 was obtained by genome library screening and it complemented a catalase-less mutant, Escherichia coli strain UM2, indicating that pBSsa1 contained the catalase gene (vktA). The vktA gene consisted of an open reading frame of 1530 bp encoding a 508 amino-acid protein with a calculated size of 57657.79 Da. The deduced amino acid sequence showed high homology with that of bacterial group III catalases. Investigation of the subcellular catalase localization using an immuno-electron microscopical technique revealed that a larger amount of VktA catalase is present in the periplasmic space than in the cytoplasm. The periplasmic space of this bacterium can therefore be regarded as a reservoir of VktA catalase in V. rumoiensis S-1.

Identification of the extracellular polysaccharide produced by the snow mold fungus Microdochium nivale

A water-insoluble, extracellular polysaccharide was isolated from the culture medium of the snow mold fungus, Microdochium nivale, that had been cultivated in potato/dextrose broth. The polysaccharide consisted of glucose only. Its Fourier transform infrared spectrum showed a beta configuration of the C1 position of glucose. Linkage analysis of the polysaccharide showed that it had a linear structure of β-(1→4)-linked glucose. The polysaccharide was therefore identified as cellulose. This is the first report of extracellular cellulose occurring in fungi.

Isolation and characterization of a novel facultatively alkaliphilic bacterium, Corynebacterium sp., grown on n-alkanes

A novel facultatively alkaliphilic bacterium that grows on a chemically defined medium containing n-alkanes as the sole carbon source was isolated from soil. The isolate was obligately aerobic, non-motile, gram-positive, and formed metachromatic granules. It was not acidfast and did not form endospores. The cell wall contained meso-diaminopimelic acid, arabinose, and galactose; the glycan moiety of the cell wall contained acetyl residues. The bacterium was catalase-positive, oxidasenegative, and the G+C content of DNA was 70.8 mol%. According to these tests, the isolate was assigned to the genus Corynebacterium. The bacterium grew well between pH 6.2 to 10.2 and the doubling time in this pH range was 4–6 h. For the growth of the isolate, added Na+ in the culture medium stimulated growth, but was not indispensable at both pH 7.2 and pH 10.2. In addition to hydrocarbons, the isolate was able to grow on a chemically defined medium containing acetate, glucose, or fructose as the sole carbon source. Analysis of reduced minus oxidized difference spectra of whole cells showed that the bacterium only possessed less than one tenth the amount of total cytochromes as compared with Bacillus alcalophilus. The above results sugest that the bacterium has characteristics different than those of the alkaliphilic Bacillus previously described.

Production of a novel exopolysaccharide by Rahnella aquatilis

A bacterium Tomakomai B-1 that was isolated from the activated sludge of a treatment process for wastewater of the pulp industry was found to produce soluble and insoluble exopolysaccharides (EPSs) when grown aerobically in a medium containing sucrose as the sole carbon source. The sugar component of soluble EPSs consisted of rhamnose, mannose, galactose, glucose, mannuronic acid, galacturonic acid and glucuronic acid, and that of insoluble EPSs consisted of rhamnose, mannose, galactose, glucose, mannuronic acid and glucuronic acid. The concentrations of insoluble and soluble EPS were approximately 1.63 and 2.58 g/l, respectively, by Erlenmeyer flask culture at 20 degrees C for 3 d with a synthetic medium containing 1% sucrose, 0.05% CaCO(3), 0.05% MgSO(4), 0.1% K(2)HPO(4), 0.0001% Na(2)MoO(4), 0.01% urea, 1.07% MES and small amounts of trace metals. Tomakomai B-1 was identified as Rahnella aquatilis. To our knowledge the production of EPSs by R. Aquatilis is reported here for the first time.