- Analysis of the Changes in Metabolic Diversity of Microbial Community in pH-gradient Microcosm
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Ahn, YoungBeom , Cho, Hong Bum , Choi, Yong Keel
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J. Microbiol. 1999;37(1):1-9.
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The Biolog redox technology was carried out for evaluation of acidification effect on microbial communities at each stage of pH gradient microcosm. While the number of heterotrophic bacterial population and activities of extracellular enzyme decreased as the pH decreased, the number of total bacteria in the microcosm was not affected. The average color development of sample at each pH-gradient showed a sigmoidal curve, and at higher pH, more overall color development appeared in Biolog plates. Average color development value in Biolog plates was stabilized at 50 hours as an optimum incubation time. The color production in the Biolog plates was caused by cell density at above pH 5.0, but by cell activity below pH 4.0. Principal component analysis of color responses revealed distinctive patterns among the pH-gradient microcosm samples.
- Electrophoretic Karyotypes of Fusarium oxysporum formae speciales
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Min, Byung Re , Kim, Kyung Ah , Choi, Yong Keel
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J. Microbiol. 1998;36(1):14-19.
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Chromosomal DNAs from nine strains of Fusarium oxysporum formae speciales were analysed by pulsed field gel electrophoresis (PFGE). Intact chromosomal DNA were prepared from fungal protoplasts. About 7-13 chromosomal DNA bands were separated in nine Fusarium oxysporum formaespeciales, ranging in size from 0.8 to 6.7 Mb. Considering that some of the chromosomal bands represented unresolved doublets, the total genome size was estimated to vary between at least 22.3 and 45.5 Mb. Gels run under different conditions were Southern blotted and probed with randomly selected genomic DNA from Fusarium oxysporum f. sp. lilii. Electrophoretix karyotyping revealed some differences within and between Fusarium oxysporum formae speciales.
- Isolation of a Bacterium That Inhibits the Growth of Anabaena cylindrica
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Kim, Chul Ho , Leem, Mi Hyea , Choi, Yong Keel
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J. Microbiol. 1997;35(4):284-289.
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A Gram (-), rod-shaped bacterium 2.3~2.8×0.45㎛ in size which exhibited growth-inhibiting effects against a cyanobacterium (Anabaena cylindrica) was isolated from Daechung Dam Reservoir. This isolate was identified as Moraxella sp. and designated Moracella sp. CK-1. Hollow zones formed around bacterial colonies on the cyanobacterial lawn. In a mixed-culture of A. cylindrica and the isolate, each microorganism grew inverse-proportionally, and the cyanobacterial vegetative cells completely disappeared within 24 hours. On treatment with Moraxella sp. CK-1, cell walls of A. cylindrica disappeared, but sheathes remained in a more electron dense form. The unit membrane such as thylakoidal membrane was stable to bacterial lysing activity. This bacterium showed a broad action spectrum against cyanobacteria. The growth-inhibiting activity of Moracella sp. CK-1 against A. cylindrica is believed to be performed through the excretion of active substances.
- Restriction pattern of the nucleic acid of Synechococcus sp. cyanophage
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Park, Jong Geun , Kim, Min , Choi, Yong Keel , Yoon, Sung Nyu
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J. Microbiol. 1996;34(1):1-6.
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The nucleic acid of Synechococcus sp. cyanophage was identified as double-stranded DNA by the result of digestion with enzymes such as exonucleases, DNase, and S1 nuclease, and by acridine orange staining. The cyanophage DNA was cleaved with several restriciton ehdonucleases such as ApaI, BamHI, Bg/II, HaeIII, Eco RI, HindIII, PstI, AND aPAI gave the clearest sets of bands on agarose gels and the fragment numbers for each were 12, 20, 29, 20, and 7, respectively. The sums of the size from Bam HI and PstI digestions were estimated approximately 227±4 kb, which are in agreement with the result of the pulsed field gel electrphoresis. This virus is thought to have the largest genosome among those of known cyanophages, which corresponds to the largest head of 90 nm when compared with the head sizes of cyanophages discovered since 1963.
- Effects of Hydrogen Ions on Aquatic Microbial Populations in Korea
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Ahn, Young Beom , Cho, Hong Bum , Choi, Yong Keel
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J. Microbiol. 1995;33(3):184-190.
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From July 1994 to March 1995, eighteen variables of physico-chemical factors including heavy metals, and of bacteria in the four reservoirs of Kyonggi-Do were investigated to examine the effects of acidic precipitation to bacterial population. The pH range in the study area is from 6.56 to 10.24, which also showed seasonal change extensively compared to other factors. The correlation analysis showed that pH has a significant positive correlation (mean 79%) with the microbial populations in Wangsong reservoir. By multiple regression analysis on all of the seasons and stations, good explanation was obtained for the variation in total direct count of bacteria (71% and 88%, respectively), and the plate count of heterotrophic bacteria (76% and 88%, respectively). In the surface water of Wansong reservoir, the variation of total count of bacteria was affected by the S/O (soluble sugar/total organic matter ratio) value and the pH, and that of the plate count of heterotrophic bacteria was explained as 63% by pH. However, in other stations they were explained by the NO₂, total organic matter (TOM), soluble sugar (SS), temperature, and dissolved oxygen as 21~91%. On the basis of the results, the bacterial populations on the media at pH 3.0, 4.0, 5.0, 6.0 and 7.0 were compared to determine the effects of acidic proceeding. All the colonies grew the best on the media of pH 7.0, but started to decrease from pH 5.0.
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