• The Plant Pathology Journal
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• 제39권5호
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• pp.417-429
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• 2023

Ralstonia solanacearum species complex (RSSC) is a soil borne plant pathogen causing bacterial wilt on various important crops, including Solanaceae plants. The bacterial pathogens within the RSSC produce exopolysaccharide (EPS), a highly complicated nitrogencontaining heteropolymeric polysaccharide, as a major virulence factor. However, the biosynthetic pathway of the EPS in the RSSC has not been fully characterized. To identify genes in EPS production beyond the EPS biosynthetic gene operon, we selected the EPS-defective mutants of R. pseudosolanacearum strain SL341 from Tn5-inserted mutant pool. Among several EPSdefective mutants, we identified a mutant, SL341P4, with a Tn5-insertion in a gene encoding a putative NDP-sugar epimerase, a putative membrane protein with sugar-modifying moiety, in a reverse orientation to EPS biosynthesis gene cluster. This protein showed similar to other NDP-sugar epimerases involved in EPS biosynthesis in many phytopathogens. Mutation of the NDP-sugar epimerase gene reduced EPS production and biofilm formation in R. pseudosolanacearum. Additionally, the SL341P4 mutant exhibited reduced disease severity and incidence of bacterial wilt in tomato plants compared to the wild-type SL341 without alteration of bacterial multiplication. These results indicate that the NDP-sugar epimerase gene is required for EPS production and bacterial virulence in R. pseudosolanacearum.

• Journal of Microbiology and Biotechnology
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• 제33권3호
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• pp.310-318
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• 2023

Microalgae are attracting much attention as promising, eco-friendly producers of bioenergy due to their fast growth, absorption of carbon dioxide from the atmosphere, and production capacity in wastewater and salt water. However, microalgae can only accumulate large quantities of lipid in abiotic stress, which reduces productivity by decreasing cell growth. In this study, the strategy was investigated to increase cell viability and lipid production by overexpressing S-adenosylmethionine (SAM) synthetase (SAMS) in the microalga Chlamydomonas reinhardtii. SAM is a substance that plays an important role in various intracellular biochemical reactions, such as cell proliferation and stress response, and the overexpression of SAMS could allow cells to ithstand the abiotic stress and increase productivity. Compared to wild-type C. reinhardtii, recombinant cells overexpressing SAMS grew 1.56-fold faster and produced 1.51-fold more lipids in a nitrogen-depleted medium. Furthermore, under saline-stress conditions, the survival rate and lipid accumulation were 1.56 and 2.04 times higher in the SAMS-overexpressing strain, respectively. These results suggest that the overexpression of SAMS in recombinant C. reinhardtii has high potential in the industrial-scale production of biofuels and various other high-value-added materials.

• The Plant Pathology Journal
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• 제39권3호
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• pp.235-244
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• 2023

Acidovorax citrulli (Ac) is a phytopathogenic bacterium that causes bacterial fruit blotch (BFB) in cucurbit crops, including watermelon. However, there are no effective methods to control this disease. YggS family pyridoxal phosphate-dependent enzyme acts as a coenzyme in all transamination reactions, but its function in Ac is poorly understood. Therefore, this study uses proteomic and phenotypic analyses to characterize the functions. The Ac strain lacking the YggS family pyridoxal phosphate-dependent enzyme, AcΔyppAc(EV), virulence was wholly eradicated in geminated seed inoculation and leaf infiltration. AcΔyppAc(EV) propagation was inhibited when exposed to L-homoserine but not pyridoxine. Wild-type and mutant growth were comparable in the liquid media but not in the solid media in the minimal condition. The comparative proteomic analysis revealed that YppAc is primarily involved in cell motility and wall/membrane/envelop biogenesis. In addition, AcΔyppAc(EV) reduced biofilm formation and twitching halo production, indicating that YppAc is involved in various cellular mechanisms and possesses pleiotropic effects. Therefore, this identified protein is a potential target for developing an efficient anti-virulence reagent to control BFB.

• The Plant Pathology Journal
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• 제39권6호
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• pp.566-574
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• 2023

The aim of this study was to investigate the regulation of lantipeptide production in Streptomyces globisporus SP6C4, which produces the novel antifungal lantipeptides conprimycin and grisin, and to identify the role of cytochrome P450 (P450) in tis regulation. To investigate the regulation of lantipeptide production, we created gene deletion mutants, including ΔP450, ΔtsrD, ΔlanM, ΔP450ΔtsrD, and ΔP450ΔlanM. These mutants were characterized in terms of their morphology, sporulation, attachment, and antifungal activity against Fusarium oxysporum. The gene deletion mutants showed distinct characteristics compared to the wild-type strain. Among them, the ΔP450ΔlanM double mutant exhibited a recovery of antifungal activity against F. oxysporum, indicating that P450 plays a significant role in regulating lantipeptide production in S. globisporus SP6C4. Our findings highlight the significant role of P450 in the regulation of lantipeptide production and morphological processes in S. globisporus. The results suggest a potential link between P450-mediated metabolic pathways and the regulation of growth and secondary metabolism in SP6C4, thereby highlighting P450 as a putative target for the development of new antifungal agents.

• 미생물학회지
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• 제47권4호
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• pp.289-294
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• 2011

Bacillus subtilis에 존재하는 DEAD-box RNA helicase 유전자의 결손이 저온 충격에 민감성을 보이는지를 조사하였다. 저온 충격에 민감한지를 알아 보기 위하여 대수기에($O.D_{600}$=0.5-0.6) 있는 세포를 $15^{\circ}C$도 낮추어 저온충격을 가하여 생장하는 정도를 조사하였다. DEAD-box RNA helicase 유전자 ydbR, yfmL, yqfR, deaD의 결손 균주들이 저온충격을 가하였을 때 ydbR 결손 균주의 생장이 야생형 균주에 비해 5배 정도 현저히 감소하였으나, 다른 DEAD-box RNA helicase 유전자의 (yfmL, yqfR, deaD) 결손은 야생형 균주와 비슷한 생장을 보였다. 저온에서의 유전자 발현을 알아보기 위하여 Northern blot으로 mRNA 양을 알아본 결과 $37^{\circ}C$에 비해 $15^{\circ}C$에서 ydbR과 yqfR의 mRNA전사물 증가를 확인할 수 있었고, 반면에 yfmL과 deaD의 전사 증가는 관찰되지 않았다. $37^{\circ}C$에서 $15^{\circ}C$로 저온 충격을 가하면 ydbR mRNA 양의 뚜렷한 증가를 확인하였고, 전사 억제제인 rifampicin를 처리하여 ydbR mRNA의 양을 조사하였을 때 $15^{\circ}C$ 조건에서는 mRNA 양이 거의 유지하는 반면에 $37^{\circ}C$ 조건에서는 급격한 mRNA의 감소가 일어나 전사과정에서 유도되기 보다는 전사 후 전사물의 안정에 기인하는 것으로 보인다. 이와 관련하여 ydbR 유전자의 5' UTR (untranaslated region) 부근에서 csp (cold shock protein) 유전자에서 관찰되는 cold box element를 확인하였고, ydbR이 저온 충격 조건에서 발현되는 과정이 csp와 유사하게 전사물의 안정성에 기인함을 알 수 있었다.

• 한국식품위생안전성학회지
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• 제38권3호
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• pp.170-175
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• 2023

본 연구에서는 MnSO₄이 B. thuringiensis의 곤충독소 형성에 미치는 영향을 분석하여 신속 검출배지 개발의 기초자료를 제안하고자 하였다. 본 실험에 사용한 균주는 순천대학교 식품위생안전실험실에 보관되어 있던 B. thuringiensis reference 1주(KCTC 1511)와 식품에서 분리된 wild type strain 9주를 사용하였다. B. thuriengiensis의 곤충독소 생성 확인은 식품의약품안전처의 곤충독소 확인시험법에 따라 실험하였다. 0.005%-MnSO₄이 첨가된 Nutrient agar는 배양 48시간에 3개 평판 중 2개 평판(66.6%)에서 곤충독소가 관찰되었고, 120시간에 3개 평판(100%) 모두에서 곤충독소가 관찰되었다. AK agar는 48시간 배양 후 3개 평판 중 1개 평판(33.3%)에서 곤충독소가 관찰되었으며, 배양 120시간에 3개 평판(100%) 모두에서 곤충독소가 관찰되었다. 이러한 결과는 포자형성에 사용되는 AK agar보다 식품공전에서 제시하고 있는 포자형성 배지인 0.005%-MnSO₄ Nutrient agar가 B. thuringiensis의 곤충독소를 신속하게 생성시키는 것으로 나타났다. B. thuringiensis 10개 균주를 24시간 배양하여 관찰한 결과, 0.000%-MnSO₄ 배지에서 10개 평판 중 1개 평판(10%), 0.001%-MnSO₄이 첨가된 배지의 10개 평판 중 2개 평판(20%)에서 곤충독소가 관찰되었다. 0.002%-MnSO₄이 첨가된 배지는 10개 평판 중 3개 평판(30%)에서 곤충독소가 관찰되었다. 0.003%-0.009%-MnSO₄이 첨가된 배지에서는 곤충독소가 관찰되지 않았다. 이러한 결과로 보아 24시간 배양 시까지는 0.002%-MnSO₄이 첨가된 Nutrient agar가 B. thuringiensis의 곤충독소를 가장 신속하게 생성시키는 것으로 나타났다. B. thuringiensis의 곤충독소는 포자형성과 동시에 생성된다는 보고와 MnSO₄이 포자형성에 기여한다는 보고를 종합하여 보면, MnSO₄이 B. thuringiensis의 포자형성을 가속화하고 이로 인해 곤충독소도 신속하게 생성된 것으로 판단된다. 따라서 B. thuringiensis의 곤충독소를 신속하게 생성하기 위해 기존 식품공전에서 제시하고 있는 Nutrient agar보다 0.002%-MnSO₄이 첨가된 Nutrient agar를 사용하는 것이 효율적일 것으로 판단된다. 그러나 Nutrient agar와 0.002%-MnSO₄ Nutrient agar의 24시간 배양 후 곤충독소 생성율의 차이는 작게 나타나 다수의 wild type B. thuringiensis를 대상으로 추가적인 연구가 필요할 것으로 판단된다.

• 동아시아식생활학회지
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• 제23권6호
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• pp.833-838
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• 2013

양조용 곰팡이 12균주에 대하여 WEB(wheat extract broth), PDB(potato dextrose broth), MEB(malt extract broth) 배지에서의 배양특성 및 전분분해 효소 활성을 조사하였다. PDB 배지에서의 균체 생산량은 1.26(R. oryzae KACC 45741)~4.80(A. oryzae KACC 46959) g/100 mL로 WEB, MEB 배지보다 각각 2.3~9.2배, 1.7~14.6배 낮았다. A. oryzae의 경우, 상업유통 균주인 Suwon, CF1001, CF1003 균주들이 야생 균주인 KACC 46421, KACC 46423, KACC 46424, KACC 46959보다 건조 균체량이 높았다. Rhizopus sp.의 산 생성량은 WEB, PDB, MEB 배지에서 각각 0.12~0.47, 0.22~1.0, 0.16~0.68%(as lactic acid)이었으며, A. oryzae는 0.06~0.11, 0.03~0.04, 0.06~0.08%(as citric acid) 범위이었다. 전분분해효소 활성은 Rhizopus sp.의 경우, R. delemer KACC 46419 균주만 WEB와 MEB에서 각각 0.013 U, 0.019 U의 활성을 보인 반면, A. oryzae의 효소 활성은 WEB, PDB, MEB 배지에서 각각 0.019~0.037, 0.017~0.033, 0.028~0.046 U 범위였다. 결론적으로 액체 종국용 배지는 균체 생산성이 비교적 우수하였고, 효소활성이 높았던 MEB 배지를 사용하는 것이 유리한 것으로 생각된다.

• 대한수의학회지
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• 제40권3호
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• pp.533-541
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• 2000

Biochemical and genetic analysis were carried out to investigate the potential recovery of pathogenecity or related mutations of Brucella abortus RB51 vaccine strains. RB51 strains were recovered from commercial vaccines, including related seed stocks from private companies in Republic of Korea, strain from USA, a reference strain from C university and a field isolate (Daehungjin) from aborted dairy cow after RB51 vaccination were compared with two identified virulent wild strains (S2308 and a field strain isolated from dairy cow in Korea) at the same conditions. All the strains examined, except identified pathogenic strains, revealed the identical characteristics to the original RB51 in biochemical properties, antigen and bacteriophage typing. Outer membrane protein (OMP) profiles from strains of RB51 showed the same patterns with standard RB51 in SDS-PAGE. In addition, Western blotting with the brucella specific monoclonal antibody also indicated that all the vaccine strains were completely deficient in their LPS compared to the pathogenic Br abortus strains. The differences in DNA structures among strains were also possible to detect after PCR. All vaccine strains, except S19, S1119-3, S1075, S544 and Br suis, were amplified a 178bp DNA fragment of eri-gene, and 364bp of IS711 elements. In contrast, 498bp DNA product was only found with Br abortus. Overall evidences in the present study confirmed that the RB51 strains for vaccine production in Korea did not originated from the phenomena of possible recovery of pathogenicity or related to any potential mutation event at all.

• Smart Structures and Systems
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• 제21권5호
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• pp.687-694
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• 2018

The problem of wheel tread defects has become a major challenge for the health management of high-speed rail as a wheel defect with small radius deviation may suffice to give rise to severe damage on both the train bogie components and the track structure when a train runs at high speeds. It is thus highly desirable to detect the defects soon after their occurrences and then conduct wheel turning for the defective wheelsets. Online wheel condition monitoring using wheel impact load detector (WILD) can be an effective solution, since it can assess the wheel condition and detect potential defects during train passage. This study aims to develop an FBG-based track-side wheel condition monitoring method for the detection of wheel tread defects. The track-side sensing system uses two FBG strain gauge arrays mounted on the rail foot, measuring the dynamic strains of the paired rails excited by passing wheelsets. Each FBG array has a length of about 3 m, slightly longer than the wheel circumference to ensure a full coverage for the detection of any potential defect on the tread. A defect detection algorithm is developed for using the online-monitored rail responses to identify the potential wheel tread defects. This algorithm consists of three steps: 1) strain data pre-processing by using a data smoothing technique to remove the trends; 2) diagnosis of novel responses by outlier analysis for the normalized data; and 3) local defect identification by a refined analysis on the novel responses extracted in Step 2. To verify the proposed method, a field test was conducted using a test train incorporating defective wheels. The train ran at different speeds on an instrumented track with the purpose of wheel condition monitoring. By using the proposed method to process the monitoring data, all the defects were identified and the results agreed well with those from the static inspection of the wheelsets in the depot. A comparison is also drawn for the detection accuracy under different running speeds of the test train, and the results show that the proposed method can achieve a satisfactory accuracy in wheel defect detection when the train runs at a speed higher than 30 kph. Some minor defects with a depth of 0.05 mm~0.06 mm are also successfully detected.

• 생명과학회지
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• 제7권1호
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• pp.30-38
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• 1997

내열성 {\alpha}$-amulase를 생산하는 미생물을 분리하기 위하여 각종 분리원으로 시료를 채취하여 55$^{\circ}C$ 이상에서 생육하고 가장 내열성 {\alpha}$-amulase 생산능이 우수한 균주를 분리, 동정한 결과 thermophilic Bacilus 속으로 추정되었다. 균체생육과 효소생산의 최적온도는 60~$65^{\circ}C$였고, 초발 pH8.0에서 가장 높은 효소생산능을 보였다. {\alpha}$-amulase 생산에 가장 양호한 탄소원은 soluble starch, dextrin, prtato starch, corn starch 등의 다당류이었으며 glucose, fructose 등의 단당류에서는 효소생산이 미약하거나 억제를 받았다. {\alpha}$-amulase 생산에 가장 중요한 질소원은 yeast extract이었따. 0.1% $CaCl_2{\cdot}2H_2O$, 0.001%의 Tween-80의 첨가는 {\alpha}$-amulase 생산성을 증가시켰다. 본 공사균이 생산한 조효소액의 특성을 검토해 본 결과, 8$0^{\circ}C$에서 최적 효소활성을 보였으며, 10$0^{\circ}C$에서도 23%의 잔존활성을 나타내었다. 최적 pH는 5.0이었다. $Ca^{2+}$은 효소활성 증진에는 영향을 미치지 않았다. 공시균으로부터 분리한 genomic DNA를 중온성 BAcillus subtilis KCTC 1024에 형질전환시킨 결과, transformant는 wild type에 비하여 약 2배의 효소활성이 증가되었다.