• Journal of Life Science
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• v.28 no.3
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• pp.369-375
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• 2018

Mycoplasma genitalium has 367 conserved genes and the smallest genome among mono-culturable prokaryotes. Conservative metabolic pathways were examined among M. genitalium and 14 prokaryotes, one hyperthermophilic exosymbiotic archaeon Nanoarchaeum equitans and 13 intracellular eubacteria of plants or insects, with fewer conserved genes than M. genitalium. They have 11 to 71 metabolic pathways, however complete metabolic pathways ranged from 1 to 24. Totally, metabolic pathway hole is very high due to the lack of 45.8% of the enzymes required for the whole metabolic pathways and it could be suggested that the shared metabolic pathway with the host's enzyme would work or the essential substances are host dependent. The number of genes necessary for mass transfer through the cell membrane is also very low, and it may be considered that the simple diffusion or the protein of the host will function in the cell membrane of these prokaryotes. Although the tRNA charging pathway was distributed in all 15 prokaryotes, each has 5-20 tRNA charging genes. This study would give clues to the understanding of the metabolic pathways of intracellular parasitic bacteria of plant and endosymbiotic bacteria of insects, and could provide basic data for prevention of crop damage, development of insect pests and human medicines.

• Korean journal of applied entomology
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• v.58 no.2
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• pp.101-109
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• 2019

An entomopathogenic bacterium, Xenorhabdus ehlersii KSY, is symbiotic to a nematode, Steinernema longicaudum, and exhibits high entomopathogenic virulence against lepidopteran insects. This study showed that the bacterial pathogenicity is induced by its inhibitory activity against eicosanoid biosynthesis of target insects, resulting in immunosuppression. To be applied for insect pest control, the bacteria should be infected to insect hemocoel. To deliver X. ehlersii to inset hemocoel, Bacillus thuringiensis (Bt) was mixed with the bacteria to breakdown the physical barrier (= midgut epithelium) from midgut lumen to hemocoel. The bacterial mixture significantly enhanced insecticidal activity of Bt only against larvae of Plutella xylostella and Maruca vitrata. For formulation, X. ehlersii cells were freeze-dried and mixed with sporulated Bt cells. The formulated bacterial mixture was applied to semi-field cultivating cabbage crop infested by P. xylostella. The bacterial mixture treatment showed over 95% control efficacy, while Bt alone gave 80% control efficacy. These results suggest that X. ehlersii can be applied to develop a novel insect control agent.

• Journal of Life Science
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• v.26 no.6
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• pp.711-720
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• 2016

To determine the degree of common genes and the phylogenetic relationships among genome-sequenced 680 prokaryotes, the similarities among 4,631 clusters of orthologous groups of protein (COGs)’ presence/ absence and gene content trees were analyzed. The number of COGs was in the range of 103–2,199 (mean 1377.1) among 680 prokaryotes. Candidatus Nasuia deltocephalinicola str. NAS-ALF, an obligate symbiont with insects, showed the minimum COG, while Pseudomonas aeruginosa PAO1, an opportunistic pathogen, represented the maximum COG. The similarities between two prokaryotes were 49.30–99.78 % (mean 72.65%). Methanocaldococcus jannaschii DSM 2661 (hyperthermophilic and autotrophic, Euryarchaeota phylum) and Mesorhizobium loti MAFF303099 (mesophilic and symbiotic, alpha-Proteobacteria class) had the minimum amount of similarities. As gene content may represent the potential for an organism to adapt to each habitat, this may represent the history of prokaryotic evolution or the range of prokaryotic habitats at present on earth. COG content trees represented the following. First, two members of Chloroflexi phylum (Dehalogenimonas lykanthroporepellens BL-DC-9 and Dehalococcoides mccartyi 195) showed a greater relationship with Archaea than other Eubacteria. Second, members of the same phylum or class in the 16S rRNA gene were separated in the COG content tree. Finally, delta- and epsilon-Proteobacteria were in different lineages with other Proteobacteria classes in neighbor-joining (NJ) and maximum likelihood (ML) trees. The results of this study would be valuable to identifying the origins of organisms, functional relationships, and useful genes.

• Korean Journal of Microbiology
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• v.55 no.1
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• pp.17-24
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• 2019

Bacteria in the polar region are under strong light and ultraviolet radiation. In this study, we investigated the effects of light on the growth of a psychrophilic bacterium, Sphingomonas sp. PAMC 26621, isolated from an Arctic lichen Cetraria sp. The growth of the strain in the light was lower than that in the dark. Surprisingly, thiamine increased the growth of Sphingomonas sp. PAMC 26621 in M9 minimal medium under light conditions. Thiamine increased the growth of the strain in a concentration-dependent manner along with ascorbic acid. N-acetylcysteine had no effect on the growth of the strain in the light. Thiamine and ascorbic acid also increased the activities of glucose-6-phosphate dehydrogenase and superoxide dismutase. The results of this study indicate that thiamine provided by the lichen symbiosis system plays an important role in light-induced oxidative stress in this Arctic bacterium as an antioxidant. Our study provide insight into the biochemistry and physiology of Arctic bacteria under strong light and ultraviolet radiation.

• KSBB Journal
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• v.30 no.3
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• pp.132-139
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• 2015

In order to use the symbiotic bacteria from ethomophatogenic nematodes as a biological control agent for agriculture, the cultural condition for maintaining phase I and antifungal activity was investigated. Symbiotic bacteria (SB) 1 stain from nematodes were selected from the three strains isolated from entomopathogenic nematodes. The growth of the SB 1 strain in NB, TSB, TY and YS medium was higher than that of the SB 2 and SB 3 strain. The packed cell volume of the SB 1 strain was reduced in NB medium which showed radical pH change. Phase I of the SB 1 strain was maintained in TSB medium after being stored for 2 weeks at $4^{\circ}C$. Culture broth with the SB 1 strain in TSB medium for 6 days and 7 days showed antifungal activities against Rhizoctonia solani KACC 40142, Botrytis cinerea Pers. KACC 40854, and Botrytis cinerea Pers. KACC 41008. Culture broth with the SB 1 strain in TSB medium containing 100 mM L-proline for 5 days showed antifungal activities against Rhizoctonia solani KACC 40142, and Botrytis cinerea Pers. KACC 40854.

• Journal of Marine Bioscience and Biotechnology
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• v.7 no.2
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• pp.42-51
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• 2015

The community structure of cultivable bacteria associated with the marine sponge, Petrosia corticata, collected from Jeju Island in summer (September) of 2012 and winter (January) of 2013, were compared by the PCR-ARDRA method. Bacterial strains were cultured for 4 days at $26^{\circ}C$ on Zobell medium and marine agar medium. After PCR amplification of 16S rRNA gene of individual strains, the restriction enzymes MspI and HaeIII were used to make restriction patterns. As a result, 24 ARDRA patterns from the summer sponge and 20 ARDRA patterns from the winter sponge were obtained. The sequencing result of 1-3 selected strains from each pattern showed over 98% similarities with the known sequences from the public database. At the phylum level, the bacterial community structures of both sponges (summer and winter) were identical qualitatively and composed of 4 phyla : Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes. Alphaproteobacteria accounted for 42.5% of total in summer sponge and 25.2% in winter, decreasing in the winter sample. Gammaproteobacteria accounted for 27.5% of total in summer sponge and 35.2% in winter, increasing in the winter sample. At the genus and species level, summer sponge had more diverse bacterial communities than winter sponge. Actinobacteria, Bacteroidetes, and Firmicutes increased in the winter sample.

• Korean Journal of Pharmacognosy
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• v.53 no.3
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• pp.119-124
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• 2022

Vaginal microbiome deeply influences vaginal health via production of messenger molecules. The healthy vaginal pH ranges between 3.5 and 4.5. However, dysbiosis of vaginal microbiome increases the pH level, leading to the incidence of vaginitis. The commensal vaginal bacterium Dermabacter vaginalis-which was isolated from the vaginal fluid of a Korean female-was incubated in acidic and neutral pH to simulate healthy and vaginitis conditions, respectively. The chemical profiles of the two different cultures were compared using HPLC. The compound showing distinctive difference between the two sets of data was presumed to be a chemical messenger, which was identified as cyclo(L-pro-L-met) by analysis of NMR, MS, and specific rotation data. Synthesis was achieved in three steps (overall yield 15%), enabling structure confirmation and antimicrobial evaluation against vaginal pathogens. Cyclo(L-pro-L-met) showed antifungal activity against Candida albicans, a major cause of vulvovaginal candidiasis.

• Korean journal of applied entomology
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• v.39 no.3
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• pp.193-197
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• 2000

Wolbachia, vertically transmitted bacterial endosymbionts, is known to induce cytoplasmic incompatibility (CI), parthenogenesis, or feminization in some insect species. The Wolbachia found to exist symbiotically as a non-virulent form in Drosophila melanogaster, however popcorn is a lethal strain of Wolbachia, which causes tissue degeneration and early death of its adult host. Popcorn-infected flies showed the delayed duration of an egg and larvae, and their pupal period and life span reduced. The oviposition and egg-hatching rate of popcorn-infected flies were decreased 15% and 80%, respectiv~ly, compared to those of the normal Wolbachia-infected flies. The pupation and emergence rates of popcorn-infected flies were 67% and 65%, respectively. When popcorn-infected flies were crossed with Wolba-chia-infected flies, and vice versa, both crosses resulted in a significant reduction in egg production, egg¬hatching, pupation, and emergence rate, and their progeny revealed the popcorn syndrome. When popcorn-infected male flies were crossed with uninfected females, popcorn was not detected in their progeny. Popcorn also maternally transmitted in flies, but it did not induce CI and affected on its host life cycle as a virulence.

• Korean journal of applied entomology
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• v.49 no.4
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• pp.409-416
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• 2010

An entomopathogenic bacterium, Photorhabdus temperata ssp. temperata (Ptt), suppresses insect immune responses and facilitates its symbiotic nematode development in target insects. The immunosuppressive activity of Ptt enhances pathogenicity of various microbial pesticides including Bacillus thuringiensis (Bt). This study was performed to select a cheap and efficient bacterial culture medium for large scale culturing of the bacteria. Relatively cheap industrial bacterial culture media (MY and M2) were compared to two research media, Luria-Bertani (LB) and tryptic soy broth (TSB). In all tested media, a constant initial population of Ptt multiplied and reached a stationary phase at 48 h. However, more bacterial colony densities were detected in LB and TSB at the stationary phase compared to two industrial media. All bacterial culture broth gave significant synergism to Bt pathogenicity against third instars of the diamondback moth, Plutella xylostella. Production of bacterial metabolites extracted by either hexane or ethyl acetate did not show any significant difference in total mass among four culture media. Reverse phase HPLC separated the four bacterial metabolites, which were not much different in quantities among four bacterial culture broths. This study suggests that two industrial bacterial culture media can be used to economically culture Ptt in a large scale.

• Korean Journal of Microbiology
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• v.50 no.3
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• pp.191-200
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• 2014

Gas hydrates play a significant role in the global carbon cycle and climate change because methane, a greenhouse gas, can be released from the dissociation of gas hydrate. Anaerobic oxidation of methane (AOM) is an important process that consumes more than 90% of the methane released into the hydrosphere and atmosphere. In this study, the microbial community associated with the methane gas hydrate sediment in the Ulleung basin, East Sea of Korea (UBGH) was analyzed by phylogenetic analysis of the mcrA and 16S rRNA gene libraries. A vertical stratification of the dominating anaerobic methane oxidizer (ANME)-1 group was observed at the surface and the sulfate methane transition zone (SMTZ). The ANME-2c group was found to be dominant in the high methane layer. The archaea of marine benthic group B, which is commonly observed in the AOM region, accounted for more than 50% of the identifications in all sediments. Nitrate reducing bacteria were predominant at SMTZ (Halomonas: 56.5%) and high methane layer (Achromobacter: 52.6%), while sulfate reducing bacteria were not found in UBGH sediments. These results suggest that the AOM process may be carried out by a syntrophic consortium of ANME and nitrate reducing bacteria in the gas hydrates of the Ulleung Basin of the East Sea.