著者

Lahiru N. Jayakody Keisuke Tsuge Akihiro Suzuki Hitoshi Shimoi Hiroshi Kitagaki

出版者

公益財団法人 応用微生物学・分子細胞生物学研究奨励会

雑誌

The Journal of General and Applied Microbiology (ISSN:00221260)

巻号頁・発行日

vol.59, no.3, pp.227-238, 2013 (Released:2013-07-17)

参考文献数

35

被引用文献数

3

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Because of the growing market for sports drinks, prevention of yeast contamination of these beverages is of significant concern. This research was performed to achieve insight into the physiology of yeast growing in sports drinks through a genome-wide approach to prevent microbial spoilage of sports drinks. The genome-wide gene expression profile of Saccharomyces cerevisiae growing in the representative sports drink was investigated. Genes that were relevant to sulphate ion starvation response were upregulated in the yeast cells growing in the drink. These results suggest that yeast cells are suffering from deficiency of extracellular sulphate ions during growth in the sports drink. Indeed, the concentration of sulphate ions was far lower in the sports drink than in a medium that allows the optimal growth of yeast. To prove the starvation of sulphate ions of yeast, several ions were added to the beverage and its effects were investigated. The addition of sulphate ions, but not chloride ions or sodium ions, to the beverage stimulated yeast growth in the beverage in a dose-dependent manner. Moreover, the addition of sulphate ions to the sports drink increased the biosynthesis of sulphur-containing amino acids in yeast cells and hydrogen sulphide in the beverage. These results indicate that sulphate ion concentration should be regulated to prevent microbial spoilage of sports drinks.

著者

Takashi Iizuka Shigeru Yamanaka Tohru Nishiyama Akira Hiraishi

出版者

公益財団法人 応用微生物学・分子細胞生物学研究奨励会

雑誌

The Journal of General and Applied Microbiology (ISSN:00221260)

巻号頁・発行日

vol.44, no.1, pp.75-84, 1998 (Released:2005-08-24)

参考文献数

47

被引用文献数

21 65

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Free-living, aerobic, copiotrophic ultramicrobacteria (UMB) that passed through a 0.45 μm membrane filter and had a cell volume of less than 0.3 μm3 were isolated from polluted urban soil by using both the direct plating method and the membrane-filter enrichment technique. The efficiency of recovering UMB from the soil was much higher in the latter method than in the former. All of the UMB isolates grew well with a doubling time of less than 6 h either in a complex nutrient medium or a chemically defined medium. The average cell volumes of the UMB isolates, as measured by scanning electron microscopy and epifluorescent microscopy with an image analysis, ranged from 0.07 to 0.22 μm3. The cell size was larger at the exponential phase of growth than at the stationary growth stage in general. Ultrathin-section electron microscopy of representatives of the UMB isolates showed that they had complete cell wall structures like typical Gram-negative or -positive bacteria. Phenotypic studies and phylogenetic analyses on the basis of 16S rDNA sequences showed that the UMB isolates were classified into three major groups, the beta and gamma subdivisions of the Proteobacteria and the Actinobacteria (the high G+C DNA group of Gram-positives). However, none of these isolates were assigned to any previously known species. These results demonstrate that free-living, relatively fast-growing, copiotrophic UMB strains undescribed so far are widely distributed in terrestrial environments, including urban soil.