• Journal of Microbiology and Biotechnology
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• 제32권11호
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• pp.1416-1426
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• 2022

The need to discover new types of antimicrobial agents has grown since the emergence of antibiotic-resistant pathogens that threaten human health. The world's oceans, comprising complex niches of biodiversity, are a promising environment from which to extract new antibiotics-like compounds. In this study, we newly isolated Pseudomonas sp. NIBR-H-19 from the gut of the sea roach Ligia exotica and present both phenotypes and genomic information consisting of 6,184,379 bp in a single chromosome possessing a total of 5,644 protein-coding genes. Genomic analysis of the isolated species revealed that numerous genes involved in antimicrobial secondary metabolites are predicted throughout the whole genome. Moreover, our analysis showed that among twenty-five pathogenic bacteria, the growth of three pathogens, including Staphylococcus aureus, Streptococcus hominis and Rhodococcus equi, was significantly inhibited by the culture of Pseudomonas sp. NIBR-H-19. The characterization of marine microorganisms with biochemical assays and genomics tools will help uncover the biosynthesis and action mechanism of antimicrobial metabolites for development as antagonistic probiotics against fish pathogens in an aquatic culture system.

• Advances in nano research
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• 제13권4호
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• pp.325-339
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• 2022

Endophytes ascertain a symbiotic relationship with plants as promoters of growth, defense mechanism etc. This study is a first report to screen the endophytic population in Waltheria indica, a tropical medicinal plant. 5 bacterial and 3 fungal strains in leaves, 3 bacterial and 1 yeast species in stems were differentiated morphologically and identified by biochemical and molecular methods. The phylogenetic tree of the isolated endophytes was constructed using MEGA X. Silver nanoparticles were biosynthesized from a rare endophytic bacterium Cupriavidus metallidurans isolated from the leaf of W. indica. The formation of silver nanoparticles was confirmed by UV-Visible spectrophotometer that evidenced a strong absorption band at 408.5 nm of UV-Visible range with crystalline nature and average particle size of 16.4 nm by Particle size analyzer. The Fourier Transform Infra-Red spectrum displayed the presence of various functional groups that stabilized the nanoparticles. X-ray diffraction peaks were conferred to face centered cubic structure. Transmission Electron Microscope and Scanning Electron Microscope revealed the spherical-shaped, polycrystalline nature with the presence of elemental silver analyzed by Energy Dispersive of X-Ray spectrum. Selected area electron diffraction also confirmed the orientation of AgNPs at 111, 200, 220, 311 planes similar to X-ray diffraction analysis. The synthesized nanoparticles are evaluated for antimicrobial activity against 7 bacterial and 3 fungal pathogens. A good zone of inhibition was observed against pathogenic bacteria than fungal pathogens. Thus the study could hold a key aspect in drug discovery research and other pharmacological conducts of human clinical conditions.

• KSBB Journal
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• 제15권1호
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• pp.100-105
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• 2000

국내에서 서식하고 있는 곤충병원성 선충 Stemernema Carpocapsae로 부터 분리$\cdot$동정된 Xenorhabdus nematophilus를 대상으로 최적배지조성과 배양조건, 상변화 특성 및 곤충 독성물질 역기를 조사하였다. 균주의 최적배치 조성은 50-70g/L yeast extract, 3 g/L $K_{2}HPO_{4}$, 1g/L $NH_{4}H_{2}PO_{4}$, 2g/L ${MgSO}_4$$\cdot$${7H}_{2}O$,10g/L NaCl 이였으며, yeast extract의 농도가 균주성장 제한인자로 작용하였다. Yeast extract 농도에 대한 비성장속도의 의존도를 Monod equation을 가정하여 비교해 본 결과, 최대 비성장속도는 0.13 $ht^{-1}$이고 Monod 상수값은 20 g/L였다. 배양 배치의 pH는 초기 6-7에 관계없이 성장이 진행됨에 따라서 약 8.5-9.5까지 증가하였으며, 7L fermentor배양에서는 균주의 비성장속도가 약 0.18 $ht^{-1}$로 flask배양보다 1.4배 더 증가하였다. 상변화의 경우 정지기에서도 fermentor배양과 flask배양 모두 약 90% 이상 phase I이 유지되었다. 한편 꿀벌부채명 나방에 대한 구강독성을 시험해 본 결과, X. nematophilus 균주를 유충사료에 첨가하면 꿀벌부채명나방 유충의 정상적인 성장을 저해하였으며, 20여일 경과 후 완전히 유충을 사멸시키는 것을 확인하였다. 배양 상등액을 유충에 직접 주사하였을 때 배양 24 시간인 지수성장기 초기에 가장 독성이 강하였으며, 배양시간이 경과함에 따라 독성이 점차 감소하였다.