- Isolation, characterization, and phylogenetic position of a new sulfur-oxidizing bacterium
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Chang, So Youn , Yoon, Joon Sik , Shin, Yong Kook , Park, Yong Ha , Park, Jin Yeol , Yang, Song Suk , Koh, Moon Joo , Yoon, Seong Myeong , Lee, Jung Sup , Lee, In Hwa , Kim, Si Wouk
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J. Microbiol. 1997;35(3):165-171.
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A sulfer-oxidizing bacterium was isolated from mine wastewater and characterized. The isolate was gram-negative, rod (0.2 × 1.2-1.5㎛), nonmotiloe, catalase positive, and oxidase positive. The optimal pH and temperature for growth were 7.0 and 30℃, respectively. The optimum thiosulfate concentration was 70 mM and the maximum growth rate was 0.081 hr. The major ubiquinone contained in the isolate was Q-8. The cellular fatty acid composition was C_16:0, C_18:1, C_17cyc, and C_19cyc as nonpolar fatty acids, and 3-OH C10 : 0 and 3-OH C_12:0 as hydroxylated fatty acids. The isolate was a facultative chemolithoautotroph which can grow autotrophically on sodium thiosulfate and sodium sulfide and which can grow heterotrophically on yeast extract. It can also grow mixotrophically on sodium thiosulfate and yeast extract. Comparison of the 16S rRNA gene sequence of the isolate with that of Thiobacillus species and Paracoccus thiocyanatus revealed that it is closely related to T. caldus which belongs to the β-subclass of the class Proteobacteria. However, the isolated could not grow at extremely low pH (pH 1-3.5). On the basis of the phenotypic, chemotaxonomic and phylogenetic data, the isolate was tentatively named Thiobacillus sp. strain C.
- Kinetic and spectral investigations on Ca^2+ and Sr^2+ containing methanol dehydrogenases
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Kim, Si Wouk , Kim, Chung, Sung , Lee, Jung Sup , Koh, Moon Joo , Yang, Song Suk , Duine, Johannis A. , Kim, Young Min
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J. Microbiol. 1997;35(3):200-205.
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Both Ca^2+ and Sr^2+ containing methanol dehydrogenases (MDH) were purified to homogeneity with yields of 48% and 42%, respectively, from Methylabacillus methanolovorus sp. strain SK5. Most of the biochemical and structural properties were similar to each other. However, some differences were found: (1) although the overall shape of the absorption spectrum of Sr^2+ MDH was very similar to that of Ca^2+ MDH, the absorption intensity originating from the cofactor in Sr^2+. MDH was higher than that in Ca^2+-MDH. Small blue shift of the maximum was also observed. These are probably due to a difference in redox state of the cofactors in Ca^2+ and Sr^2+ -MDH; (2)Sr^2+ -MDH was more heat-stable than Ca^2+-MDH above 56℃; (3) the V_max values for the methanol-dependent activities of Sr^2+ Ca^2+ -MDH in the presence of 3 mM KCN were 2.038 and 808 nmol/mg protein/min, respectively. In addition, the K_m values of Sr^2+ and Ca^2+ MDH for methanol were 12 and 21 uM, respectively; (4) the endogenous activity of Ca^2+ -MDH was more sensitive than that of Sr^2+ -MDH in the presence of cyanide; (5) Diethyl pyrocarbonate treatment increased the enzyme activities of Ca^2+ and Sr^2+ MDH 4.2 and 1.4 folds, respectively. These results indicate that Sr^2+ stabilizes the structural conformation and enhances the activity of MDH more than Ca^2+.
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