• 한국미생물·생명공학회지
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• 제38권2호
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• pp.117-123
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• 2010

BT toxin is produced by a soil bacterium Bacillus thuringiensis and has long been used as a biological insecticide without any competition. Recently, Photorhabdus, a symbiotic bacterium from entomopathogenic nematodes, family Heterorhabditae, has been researched and discussed as alternatives to B. thuringiensis. Photorhabdus, which lives in the gut of entomopathogenic nematodes, is a highly virulent pathogen of a wide range of insect larvae. When an insect is infected by the nematodes, the bacteria are released into the cadaver, and produce a number of insecticidal toxins. The biological role of the different Photorhabdus toxins in the infection process is still unclear. Photorhabdus toxin complex (Tc) is highly secreted gut-active toxin and has been characterized as a potent three-component (A, B and C) insecticidal protein complex. These components are necessary for full oral activity against insect larvae. The Photorhabdus PirAB binary toxins exhibit a potent injectable activity for Galleria mellonella larvae, and have oral toxicity against mosquitoes and caterpillar pest Plutella xylostella. Other toxin, 'makes caterpillars floppy' (Mcf) showed injectable activity on caterpillars. Recombinant Mcf triggers apoptosis in both insect hemocytes and the midgut epithelium and carries a BH3 domain. In this review, the relationship between the Photorhabdus and the nematode is discussed and recent important insecticidal toxins from Photorhabdus are described.

• 미생물학회지
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• 제29권4호
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• pp.250-257
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• 1991

An obligate methanol-oxidizing bacterium, Methylobacillus sp. strain SK1, which grows only on methanol was isolated from soil. The isolate was nonmotile Gram-negtive rod. It does not have internal membrane system. The colonies were small, whitish-yellow, and smooth. The guanine plus cytosine content of the DNA was 48 mol%. Cellular fatty acids consisted predominantly of large amounts of straight-chain saturated $C_{16:0}$ acid and unsaturated $C_{16:1}$ acid. The major ubiquinone was Q-8, and Q-10 was present as minor component. The cell was obligately aerobic and exhibited catalase, but no oxidase, activity. Poly-.betha.-hydroxybutyrate, endospores, or cysts were not observed. the isolate could grow only on methanol in mineral medium. Growth factors were not required. The isolate was unable to use methane, formaldehyde, formate, methylamine, and several other organic compounds tested as a sole source of carbon and energy. Growth was optimal at 35.deg.C and pH 7.5. It could not grow at 42.deg.C. The doubling time was 1.2h at 30.deg.C when grown with 1.0%(v/v) methanol. The growth was not affected by antibiotics inhibiting cell wall synthesis and carbon monoxide but was completely suppressed by those inhibiting protein synthesis. Methanol was found to be assimilated through the ribulose monophosphate pathway. Cytochromes of b-, c-, and o- types were found. Cell-free extracts contained a phenazine methosulfate-linked methanol dehydrogenase activity, which required ammonium ions as an activator. Cells harvested after the late exponential phase seemed to contain blue protein.ein.

• 미생물학회지
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• 제25권4호
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• pp.339-345
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• 1987

A bacterium K-4-3, producing $\beta$-glucan hydrolyzing enzyme, was isolated from soil and identified to be Bacillus subtilis by its morpholohical and physiological characteristics. $\beta$-glucan was coloured using cibacron blue 3G-A and cross linded by the addition of 1, 4-butanedioldiglycidyl ether. This substrate was used for the isolation of $\beta$-glucanase producing microorganism. The $\beta$-glucan hydrolyzing enzyme actibity from isolated K-4-3 strain was also measured using the modified substrate. Bacillus subtilis K-4-3 produced the highest extracellular $\beta$-glucan hydrolyzing activity in the basal medium containing $\beta$-glucan as a carbon source, peptone and tryptone as a nitrogen source, and magnesium sulfate as an inorganic salt. The optimum temperature and initial pH for $\beta$-glucanase production by Bacillus subtilis K-4-3 were $37^{\circ}C$ and pH6. The highest enzyme activity was obtained at the culture age of 54 hrs with rotary shaking at $37^{\circ}C$. The crude enzyme showed the highest activity at pH 7.5-8.0 and $65^{\circ}C$.

• 미생물학회지
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• 제31권3호
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• pp.179-183
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• 1993

A restricted facultatively methanol-oxidizing bacterium, Methylovorus sp. strain SS1, was isolate dfrom soil samples from Kuala Lumpur, Malaysia, through methanol-enrichment culture technique. The isolate was nonmotile Gram-negative rod and did not have complex internal membrane system. The colonies were small, pale-yellow, and raised convex with entire margin. The cell did not produce any spores and capsular materials. The cell was obligately aerobic and exhibited catalase, but no oxidase, activity. Plasmid, carotenoid pigment, and poly-.betha.-hydroxybutyric acid were not found. The guanine plus cytosine content of the DNA was 55%. The isolate was found to grow only on methanol methylamine, or glucose. Growth factors were not required. Cells growing on methanol was found to produce extracellular polysaccharides containing glucose, lactose, and fructose. Growth was optimal (t$_{d}$= 1.7) with 0.5%(v/v) methanol at 40.deg.C and pH 6.5. No Growth was observed at over 60.deg.C. Cell-free extracts of the methanol grown cells exhibited the phenazine methosulfate-linked methanol dehydrogenase activity Methanol was found to be assimilate dthrough the ribulose monophosphate pathway.y.

• 한국환경보건학회지
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• 제34권5호
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• pp.387-394
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• 2008

The toxicity of methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA) and formaldehyde (FA) on the indigenous microbial community in forest soil was studied. MTBE, TBA and FA with different concentrations were added into microcosms containing forest soil samples. After 10 and 30 days, total viable cell number and dehydrogenase activity in the microcosms were evaluated. Bacterial communities in the microcosms were also analyzed using a denaturing gradient gel electrophoresis (DGGE). Dehydrogenase activity and total viable cell number were decreased according to the increase of MTBE, TBA and FA concentrations (P<0.05). FA toxicity was the highest, but TBA toxicity was the lowest. The results of principal component analysis using DGGE fingerprints showed that the microbial communities contaminated MTBE, TBA and FA were grouped by exposure time not exposure concentration. Dominant species in the microcosms were as follows: Photobacterium damselae sub sp. and Bacillus sp. KAR28 for MTBE; Mycobacterium sp. and Uncultured Clostridium sp. for TBA; and Uncultured Paenibacillaceae bacterium and Anxynobacillus, Flavithermus for FA.

• 한국환경과학회지
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• 제18권11호
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• pp.1261-1270
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• 2009

Fifty hydrocarbon-metabolizing microorganisms were isolated from soil samples polluted by the petroleum oils in Gamman-dong, Busan. Among them, strain 2-3A, showing strong emulsification activity, was selected by oil film-collapsing method. This bacterium was identified as Acinetobacter sp. and designated as Acinetobacter sp. 2-3A. The optimum temperature and pH on the growth of Acinetobacter sp. 2-3A were $25^{\circ}C$ and pH 7.0, respectively. The carbon and nitrogen sources for the most effective emulsification activity were 3.0% olive oil and 0.5% peptone, respectively. The 0.15% potassium phosphate was the most effective emulsification activity as a phosphate source. The optimum emulsification activity condition was $20^{\circ}C$, pH 7.0, and 2.0% NaCl. The optimum time for the best production of biosurfactant was 27 hrs. The emulsification stability was maintained at the temperature range from $4^{\circ}C$ to $100^{\circ}C$, pH range from 6.0 to 10.0, and NaCl range from 0% to 10%. For the oil resolvability of the biosurfactant, the residual oils were investigated by gas chromatography. As a result, it was verified that the biosurfactant decreased and decomposed crude oils from $_nC_{10}$ to $_nC_{32}$.

• 식물병연구
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• 제29권4호
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• pp.399-404
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• 2023

Agricultural activities and the number of farms in the subarctic regions have been increasing annually after the coronavirus disease 2019 pandemic to achieve food self-sufficiency. Potatoes are vulnerable to soft rot bacteria at all stages of production, storage, and transportation. A novel bacterium, Pseudomonas sp. N3-W, isolated from Alaska tundra soil, grows at 5-25℃ and produces extracellular protease(s). N3-W caused necrotic spots (hypersensitivity) in hot pepper leaves and soft rot disease (pathogenicity) in potato tubers. The psychrotolerant N3-W caused significant soft rot symptoms on potatoes at a broad temperature range (5℃, 15℃, and 25℃). In contrast, mesophilic Pectobacterium carotovorum KACC 16999 induced severe rotting symptoms in potatoes at their optimal growth temperature of 15℃ and 25℃. However, it barely produced symptoms at 5℃, which is the appropriate storage and transportation temperature for potatoes. The results of pathogenicity testing imply that psychrotolerant soft rot pathogens from polar regions may cause severe soft rot not only during the crop growing season but also during storage and transportation. Our study indicates the possibility of new plant pathogen emergence and transmission due to the expansion of crop cultivation areas caused by permafrost thawing in response to recent polar warming.

• 한국초지조사료학회지
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• 제19권1호
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• pp.31-40
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• 1999

본 시험은 병원성 사상균에 길항작용이 있고 식물의 생육을 촉진하는 세균을 이용하여 연작 및 비연 작토양에 있어서 옥수수(Zea may L.)의 생산성을 증대시킬 수 있는 방안을 제시하고자 수행되었다. 옥수수는 전남대학교 농과대학 부속동물사육장내 vinyl house에서 자연광 상태에서 $pot(30{\times}50cm)$로 재배한 다음 파종 후 50일 및 90일에 수확하여 건물중을 조사하였으며, 시험토양은 연작 및 비연작지의 양토와 버미큘라이트를 1:1 로 혼합하여 사용하였다. 본 시험에 이용된 세균은 목초근권에서 직접 분리한 Bacillus subtilis 였다. 연작 및 비연작 토양 모두 B. subtilis 처리구에서 옥수수의 건물중이 B. subtilis 무처리구보다 그리고 병원성 사상균 처리구보다 증가되었다. 그리고 비연작 토양에서 생장한 옥수수의 건물중은 연작토양에서 보다 증가하였다. 옥수수의 생장에 있어서 B. subtilis 접종효과는 연작토양보다 비연작토양에서 좋게 나타났다. 그러나 연작 및 비연작토양 모두 병원성사상균을 접종함으로써 옥수수의 건물중은 현저하게 감소되었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제12권6호
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• pp.70-77
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• 2007

토양에 존재하는 다핵방향족탄화수소(Polycyclic Aromatic Hydrocarbons, PAHs)의 처리를 위하여 자연계로부터 분리된 균주는 Pseudomonas sp.로 동정되었으며, 이 균주를 KM1으로 명명하였다. 균주의 최적 성장조건은 회분식 배양에서 $35^{\circ}C$, pH 7로 나타났다. 분리균주 Pseudomonas sp. KM1에 의한 7-PAHs(naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, fluoranthene and pyrene)의 분해실험결과 배양 1일 만에 fluoranthene을 제외한 naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene and pyrene 이 분해됨을 확인할 수 있었다. 그리고 토양유무에 따른 PAHs 분해실험 결과, 흡착분배계수와 유기물함량(%)이 큰 신동방이 경방이나 봉동보다 분리균주에 의한 생분해율(%)이 낮았다. 토양에 오염된 유기화합물의 분배특성과 토양 내 유기물함량(%)이 오염된 토양의 생물학적 처리효과에 영향을 미치는 중요한 인자인 것으로 나타났다.

• 한국미생물·생명공학회지
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• 제51권2호
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• pp.203-207
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• 2023

옥수수 근권 토양으로부터의 N₂O 환원 근권세균인 Pseudomonas sp. M23을 분리하였다. M23 균주의 최대 N₂O 환원속도는 15.6 mmol·g-dry cell^-1·h^-1이었다. M23 균주의 N₂O 환원 활성은 디젤 오염물에 의해 저해받지 않았고, 옥수수와 톨페스큐 뿌리삼출물 첨가에 의해 향상되었다. M23 균주 접종은 옥수수와 톨페스큐를 이용한 디젤 오염 토양의 정화 효율을 저해하지 않았다. M23 균주를 접종한 토양에서 재배한 식물체의 뿌리무게는 미접종 토양에서의 뿌리무게보다 컸으나, 유의적 차이는 없었다. 이러한 결과는 Pseudomonas sp. M23이 유류 오염 토양의 근권정화 과정에서 N₂O 배출을 저감하는데 활용 가능한 유용한 세균임을 시사한다.