• The Korean Journal of Mycology
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• v.46 no.1
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• pp.75-82
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• 2018

Totally 91 strains of wild yeasts were isolated from the humus rich soil in the Bogyong city park of Daejeon city, Korea. Majority of the strains belonged to Cryptococcus spp., which included 11 strains of Cryptococcus aureus. Among them, Kwoniella mangroviensis JSS0500, Candida corydalis JSS0501, Candida bombi JSS0503, Candida multigemmis JSS0504, Cryptococcus dimennae JSS0506, Cryptococcus saitoi JSS0507, Cryptococcus victoriae JSS0508, Metschnikowia pulcherrima JSS0502, Papiliotrema aurea JSS0505, Debaryomyces vanrijia JSS0509, Occultifur externus JSS0510, Filobasidium floriforme JSS0511 and Yamadazyma scolyti JSS0512 represented newly recorded yeast strains in Korea, and their microbiological characteristics were investigated. All of these unrecorded yeasts showed oval shape and also formed ascospores and pseudomycelia, except for Kwoniella mangroviensis JSS0500, Candida bombi JSS0503, and Metschnikowia pulcherrima JSS0502. Seven strains including Candida corydalis JSS0501 grew in vitamin-free medium, and 4 of the wild yeasts including Cryptococcus victoriae JSS0508 were halotolerant, i.e., capable of growing in 10% NaCl-containing yeast extract-peptone-dextrose (YPD) broth. Debaryomyces vanrijia JSS0509 was found to be a thermophilic yeast that grew at $37^{\circ}C$.

• The Korean Journal of Mycology
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• v.48 no.2
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• pp.151-160
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• 2020

The goal of this study was to investigate the diversity present among wild yeasts obtained from soils of spice fields and from mountain soils, and to further, characterize previously unrecorded novel wild yeast strains. In total, 36 strains from 17 different species of wild yeasts were isolated from 35 soil samples obtained from garlic fields of Geumsan, Chungcheongnam-do, Korea. Among these, six yeast strains of Trichosporon moniliiforme, and four strains each of Papiliotrema flavescens and Candida melibiosica species were isolated. Additionally, 22 strains of 18 different species of wild yeasts were isolated from 32 soil samples collected from the ballonflower and ginger fields of Geumsan, Korea. Finally, 46 strains of wild yeasts were isolated from 35 soil samples obtained from Mt. Daedun in Geumsan, Korea. Among the total of 106 isolated wild yeast strains, 10 strains, including Debaryomyces vindobonensis GHY31-3 represented novel yeast strains which were previously unrecorded. All the 10 previously unrecorded yeasts were oval or global in shape, and five strains, including Filobasidium stepposum SFG1-4 formed ascospores. Three strains, including Pseudozyma alboarmeniaca CD 23-5 grew well in vitamin-free medium. Cell-free extract obtained from Filobasidium magnum SFG1-3 indicated 28.6% of xanthine oxidase inhibitory activity.

• Korean Journal of Microbiology
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• v.27 no.4
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• pp.357-365
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• 1989

Induction conditions for autolysis and autoplast formation of thermophilic Clostridium thermohydrosulfuricum were studied. The cells in the initial exponential growth phase were well autolysed in Tris-HCl buffer or inorganic buffers containing univalents, such as $K^{+}$ and $Na^{+}$ , and chemicals such as cysteine-HCl, sorbitol and glycerol. Meanwhile, autolysis induction was slightly inhibited by divalents, such as $Mg^{2+}, Mn^{2+}, Ca^{2+}, Ni^{2+}$, and strongly by divalents, such as $Fe^{2+}, Cu^{2+}$ and citric acid. The autolysis was stimulated when the cells were grown in the medium containing ampicillin that inhibites cell wall synthesis, meanwhile, it was slightly inhibited by nucleic acids and protein synthesis inhibitors. The optimal pH and temperature for the induction of autolysis were 7.5 and $60^{\circ}C$, respectively. On the other hand, the cells were autoplasted without lysozyme treatment during autolysis due to the stabilization of protoplasmic membrane in the presence of divalents such as $Mg^{2+}, Mn^{2+}, Ca^{2+}, Ni^{2+}$. Autoplast formation was mostly induced at $37^{\circ}C$ in 50mM Tris-HCl buffer (pH 7.5) containing 20 mM $MgCl^{2}$ and 0.3 M glycerol, and in the late exponential growth phase growing cell.

• Korean Journal of Microbiology
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• v.42 no.3
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• pp.216-222
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• 2006

This study was carried out to select the lactic acid bacteria producing ${\beta}-galactosidase$ (lactase) and investigate the properties of the ${\beta}-galactosidase$. About 100 strains of lactic acid bacteria showing blue colony on the MRS agar medium containing X-gal were isolated from several kinds of Kimchi. Among them, 2 strains were selected as potential ${\beta}-galactosidase$ producers. The selected strains, ET-1 and LA-12, were identified as Lactobacillus fermentum and L. acidophilus, respectively by the analysis of 16S rDNA sequences. They showed relatively high ${\beta}-galactosidase$ activity and cellular viability. Their ${\beta}-galactosidase$ showed the highest activity at $55^{\circ}C$. And the optimum pHs of the enzymes produced by ET-1 and LA-12 were pH 5.5 and pH 7.0, respectively. They were also highly resistant to artificial gastric juice and bile. Two selected strains showed little change of viable cell number for 3 hr incubation in artificial gastric juice, and maintained the viable cell number at $10^8CFU/ml$ for 24 hr in 0.3% oxgall after incubation for 2 hours in artificial gastric juice. Based on these results, ET-1 and LA-12 are expected to be applied in dairy industry.

• Korean Journal of Microbiology
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• v.52 no.2
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• pp.212-219
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• 2016

Forty-nine pigments were extracted from the collections of 106 pigment producing bacteria from the plant rhizosphere soil. Antibacterial activity test was performed in the subjects of the extracted pigments with plant pathogenic bacteria including Xanthomonas axonopodis and Xanthomonas campestris, and with plant pathogenic fungi including Botrytis cinerea, Colletotrichum acutatum, and Fusarium oxysporum. The yellow pigment by Chryseobacterium sp. RBR9 and the red pigment by of Methylobacterium sp. RI13 showed the antibacterial activities against Xanthomonas axonopodis and Xanthomonas campestris. The violet pigment by Collimonas sp. DEC-B5 showed the antibacterial activity as well as the antifungal activities against Botrytis cinerea and Fusarium oxysporum. Especially, the violet pigment inhibited the growth of Botrytis cinerea more than 65% at MIC $20{\mu}M$. Upon the HPLC analysis result for the isolation of pigment with antifungal activity, violacein (91.6%) and deoxyviolacein (8.4%) were isolated for the pigment by Collimonas sp. DEC-B5. The production amount of the pigment was increased more than 10 times higher when D-mannitol 1.5% and yeast extract 0.2% were added as the nitrogen source to SCB medium. This study suggests that produced violacein by Collimonas sp. DEC-B5 will be effective to control strawberry gray-mold rot fungi by its preventive activity.

• Korean Journal of Microbiology
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• v.44 no.4
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• pp.326-332
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• 2008

Various bacteria were isolated from Korean soil samples based on their capability inhibiting the growth of MRSA strains. Among them, strain YK5 with the highest activity was a Gram positive sporulative bacillus with motility. It did not produce indole and no acid was formed from mannitol by the bacterium. The 16S rRNA sequence of the strain showed $95{\sim}98%$ homology with those of Paenibacillus spp.. The bacterial isolate shared the highest homology with that of P. elgii (98%), but was named as Paenibacillus incheonensis YK5 due to differences in physiological properties. Butanol extract of the P. incheonensis YK5 culture grown in SST medium at $37^{\circ}C$ for 96 hr showed a broad antimicrobial activity against Gram-positive (MRSA and Streptococcus pneumoniae) and negative (Pseudomonas aeruginosa, Salmonella spp., Shigella spp., Escherichia coli, Klebsiella pneumoniae) pathogenic bacteria and fungi (Cryptococcus neoformans and Trichophyton). The antimicrobial activity in the crude extract was stable in a broad range of temperature and pH, $20{\sim}100^{\circ}C$ and $3.0{\sim}6.0$, respectively. Therefore, the antimicrobial activity of P. incheonesis YK5 had potential as a novel antibiotics for pathogens including MRSA.

• Korean Journal of Microbiology
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• v.50 no.4
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• pp.302-307
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• 2014

Many rhizobacteria can promote plant growth through various direct or indirect mechanisms, and their production of phytohormones such as indole-3-acetic acid (IAA) may have pronounced effects on growth and development of plants. Rhizobacterial strain isolated from rhizosphere of foxtail (Setaria viridis), Acinetobacter sp. SW5 produced 118.1 mg/L of IAA and 4.5 mg/L of gibberellin ($GA_3$) in brain heart broth medium at 2 and 1 day of incubation, respectively. In a pot test the lengths of stem and root and fresh weight of the germinated tomato seedlings treated with Acinetobacter sp. SW5 significantly increased by 26.3, 33.3, and 105.3%, respectively compared to those of the uninoculated control in 12 weeks of cultivation. When the root exudate secreted from tomato seedlings was analyzed by HPLC, 3.75 ng mg tomato $root^{-1}$ of tryptophan which is an IAA precursor was detected. Acinetobacter sp. SW5 could produce $4.06{\mu}M$ of IAA from root exudate from 8 tomato seedlings. Together with the capability of growth of Acinetobacter sp. SW5 in the tomato root exudates, this IAA secreted by bacteria might contribute to enhance the growth of tomato plants.

• Korean Journal of Microbiology
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• v.36 no.3
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• pp.203-208
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• 2000

A Baczllus circdans KCTC3004 $\alpha$-amylase gene contained in a recombinant plasmid pAL850 was transferred into a new shuttle vector plasmid pALSIlI by ligating linearlzed DNAs of pUC19 and pUB110. B. subtilis RM125 and B. megatenurn ATCC14945 transfonned with pALS111 produced the $\alpha$-amylase substantially Most of the enzyme was produced during the exponential growth period. The maxiinurn activities of the $\alpha$-amylase produced by the Bucillus transformants were compared with that of the B. circulans gene donor strain. The B. subtilis RM125(pALS111) enzyme showed the actlvicy 95 times higher than that of the gene donor cells, followed by the B, nzegaterium ATCC14945(pALSlll) enzyme with activity 34 limes higher than that of the gene donor cells. While E coli secreted about 10% of the produced enzyme, B. subtilis excreted the enzyme inlo the medium wholly and B. megaterirun about 98% ofthe total product. The plasmid pALSI11 was quite stable inB. nzegaterium (92%), inoderately stable in B. subtilis (76%), but was unstable in E. coli (38%). The SDS-PAGE and zymogram of this enzyme produced in E. coli(pALS111), B. subtilis( pALS111) or B. megateril~m (pALS111) indicated a molecular weight of 55,000. The enzymes overproduced in three different host cells hydrolyzed starch to produce mainly maltoaiose and mallooligosaccharides.

• Korean Journal of Microbiology
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• v.7 no.1
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• pp.10-21
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• 1969

The effect of glucose and 2-thiobarbituric acid on the biosynthesis of cell constituents such as protein, carbohydrate, DNA, RNA, phospholipid and PCA-soluble phosphate compounds in Chlorella duing the life cycle was measured, and the changes in the content of these main cellular components of the algal cell were analyzed in connection with the nuclear and cytoplasmic divison. In the normal autotrophic synchronous culture the contents of protein, RNA, and DNA in the cell showed a chracteristic changes according to the progress of cell development, increasing more or less throughout all the life cycle. The synthesis of protein is more prominent in the division period nad that of DNA is more active in the ripening period, while the synthesis of RNA is more rapid in the growing and ripening periods than other developmental stages. The period of division cycle was little affected by glucose in the medium, although the synchrony of the growth and cellular division was disturbed and the n value increased. The cotents of protein, carbohydrate, RNA nad DNA of the cell were increased by the glucose treatment throughout all the life cycle. On the other hand, both of cellular growth and division were retarded severely and the n value was decreased by the 2-thiobarbituric acid treatment throughout all the life cycle. On the other hand, both of cellular growth and division were retarded severely and the n value was decreased by the 2-thiobarbituric acid treatment. The synthesis of protein, carbohydrate, DNA, RNA and phospholipid of the cell was also retarded by 2-thiobarbituric acid. In the autotrophic, mixotrophic and 2-thiobarbituric acid-treated cultures, each having different mode cytoplasmic division, a common general schema occurring in the cell during the life cycle may be drawn as follows. The ratio of RNA to protein attains maximum value in the $L_1$-cell stage prior to the nuclear division and thereafter decreases during the periods of ripening and division. The ratio of PCA-soluble phosphate compounds to protein increased from the begining of the culture to $L_4$-cell stage successively and thereafter decreased gradually during the division period, while the ratio of protein to DNA kept almost constant up to the division period and thereafter increased during the division period. Therefore, it is presumed that the increase in the ratio of RNA to protein is to be an inducer of nuclear division and that the cytoplasmic division is induced by the increase in the ratio of protein to DNA.

• Korean Journal of Microbiology
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• v.54 no.3
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• pp.266-271
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• 2018

Effect of plasmid curing of Acinetobacter sp. B-W on the production of siderophore from glutamic acid as both carbon and nitrogen sole sources was investigated. Plasmid cured mutant of strain B-W lost the ability to produce siderophore from glutamic acid at $28^{\circ}C$. Transformant E. coli $DH5{\alpha}$ harboring 20 kb plasmid, that was isolated from wild type of strain B-W produced siderophore from glutamic acid as both carbon and nitrogen sole sources at $28^{\circ}C$, but, not at $36^{\circ}C$. Production of siderophore from glutamic acid by transformant E. coli $DH5{\alpha}$ was completely inhibited by $10{\mu}M\;FeCl_3$. In previous report, catechol nature of siderophore produced from glutamic acid by strain B-W was detected by Arnow test. The siderophore produced from glutamic acid by transformant E. coli $DH5{\alpha}$ was also catechol type. Rf value of siderophore produced from transformant E. coli $DH5{\alpha}$ grown in medium glutamic acid as both carbon and nitrogen sole sources at $28^{\circ}C$ was 0.32 in butanol-acetic acid-water (12:3:5) as developing solvent. Rf value of the siderophore was the same with that of wild type of strain B-W. Thus a single plasmid of 20 kb seemed to be involved in the production of siderophore from glutamic acid.