• Journal of Veterinary Science
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• 제21권2호
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• pp.19.1-19.10
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• 2020

Given that the current Newcastle disease virus (NDV) infection in wild birds poses the threat to poultry, surveillance of Newcastle disease in captive wild birds was carried out in Jilin, China in 2018. Here, an NDV strain obtained from toco toucan was firstly characterized. The results showed that the F gene of the NDV isolate Toucan/China/3/2018 is classified as genotype II in class II. Sequence analysis of the F0 cleavage site was ¹¹³RQGR/L¹¹⁷, which supports the result of the intracerebral pathogenicity index assay indicating classification of the isolate as low-pathogenicity. Experimental infection demonstrated that Toucan/China/3/2018 can effectively replicate and transmit among chickens. To our knowledge, this is the first report on genetically and pathogenically characterizing NDV strain isolated from toucan, which enriches the epidemiological information of NDV in wild birds.

• Microbiology and Biotechnology Letters
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• 제29권2호
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• pp.96-103
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• 2001

Phaffia rhodozyma is the most promising microbial source of astaxanthin production, though wild-type strains are needed to increase the astaxanthin content for commercial production. To increase astaxanthin content for commercial production, a mutant strain of P. rhodozyma was selected and culture conditions of the mutant selected were optimized. P. rhodozyma was treated with mutagenic agent such as NTG, acriflavine, and UV in serial order and carotenoids hyper-producing mutant strain was selected based on the capabilities of cell growth on the agar plate containing chemical inhibitors and carotenoids production. Among the mutants tested, a mutant WS-2 was finally selected. Mutant WS-2 produced 1.26mg carotenoids/g-dry cell weight and this value was about- 4-folds higher than that of wild-type. The optimum culture conditions were $24^{\circ}C$ of temperature, 1.5vvm of aeration and 300rpm of agitation. In the optimized condition, cell and carotenoids concentrations were 7.62g/l and 14.9mg/l, respectively.

• Microbiology and Biotechnology Letters
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• 제23권4호
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• pp.390-396
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• 1995

Bacillus sphaericus 1593 is a larvicidal toxin-producing mosquitocidal bacterium. The toxin contains a parasporal crystalline inclusion which is composed of a protein that is activated under alkaline condition. To enhance alkaline environment around toxin protein, cryptic plasmid cured, B. sphaericus 1593 was transformed by the Bacillus pasteurii urease gene which generate ammonia from urea. Transformant produced urease at about 80% more than wild type strain. B. sphaericus 1593, and the urease gene was stably maintained. It also produced crystalline toxin protein at the same level as the wild type strain B. sphaericus 1593.

• Journal of Microbiology and Biotechnology
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• 제5권4호
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• pp.241-243
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• 1995

A lipopolysaccharide (LPS) defective mutant of Bradyrhizobium japonicum was characterized in terms of its cell surface hydrophobicity (CSH). By monitoring the kinetics of adhesion to hexadecane the LPS mutant was found to be far more hydrophobic than the wild type strain; the removal coefficients were 4.65 $min^{-1}$ for the mutant, as compared with only 2.40 $min^{-1}$ for the wild type. The possible role of cell surface hydrophobicity of B. japonicum in nodulation process is discussed.

• Journal of Microbiology and Biotechnology
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• 제13권4호
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• pp.564-570
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• 2003

The antibacterial mechanism of enterobacter Salmonella typhimurium was studied. The rfa (Waa) gene cluster of S. typhimurium encodes the core oligosaccharide biosynthesis of lipopolysaccharide (LPS). Among the rfa gene cluster, we recently cloned the rfaE gene, which is involved in ADP-L-glycero-D-manno-heptose biosynthesis. The rfaE mutant synthesizes heptose-deficient LPS, which consists of only lipid A and 3-deoxy-D-manno-octulosonic acid (KDO), thus making an incomplete LPS and a rough phenotype mutant. S. typhimurium deep-rough mutants with the heptose region of the inner core show a reduced growth rate, sensitivity to high temperature, and hypersensitivity to hydrophobic antibiotics such as baicalin isolated from the medicinal herb of Scutellaria baicalensis Georgi. Thus, in this study, the cloned rfaE gene was added to the S. typhimurium rfaE mutant strain SL1102 (rfaE543), which makes heptose-deficient LPS and has a deep-rough phenotype. The complementation created a smooth phenotype in the SL1102 strain. The sensitivity of SL1102 to bacteriophages was also recovered to that of wild-type strain, indicating that LPS is used as the receptor for bacteriophage infection. The permeability barrier of SL1102 to hydrophobic antibiotics such as novobiocin and baicalin was restored to that of the wild-type, suggesting that antibiotic resistance of the wild-type strain is highly correlated with their LPS. Through an agar diffusion assay, the growth-inhibition activity of baicalin was fully observed in the mutant SL1102 strain. However, only a half of the inhibitory activity was detected in the rfaE complemented SL1102 strain. Furthermore, the LPS produced by the rfaE-complemented SL1102 strain was indistinguishable from LPS biosynthesis of smooth strains.

• Proceedings of the Korean Society of Food Hygiene and Safety Conference
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• 한국식품위생안전성학회 2001년도 The Asia-Pacific Conference on Reproductive Biology and Environmental Sciences
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• pp.157-158
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• 2001

• Mycobiology
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• 제39권1호
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• pp.20-25
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• 2011

Spores of Aspergillus sp. SU14 were treated repeatedly and sequentially with $Co^{60}$ ${\gamma}$-rays, ultraviolet irradiation, and N-methyl-N'-nitro-N-nitrosoguanidine. One selected mutant strain, Aspergillus sp. SU14-M15, produced cellulase in a yield 2.2-fold exceeding that of the wild type. Optimal conditions for the production of cellulase by the mutant fungal strain using solid-state fermentation were examined. The medium consisted of wheat-bran supplemented with 1% (w/w) urea or $NH_4Cl$, 1% (w/w) rice starch, 2.5 mM $MgCl_2$, and 0.05% (v/w) Tween 80. Optimal moisture content and initial pH was 50% (v/w) and 3.5, respectively, and optimal aeration area was 3/100 (inoculated wheat bran/container). The medium was inoculated with 25% 48 hr seeding culture and fermented at $35^{\circ}C$ for 3 days. The resulting cellulase yield was 8.5-fold more than that of the wild type strain grown on the basal wheat bran medium.

• Journal of Microbiology and Biotechnology
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• 제20권4호
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• pp.718-726
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• 2010

A selected fungal strain, for production of the raw-starchdigesting enzyme by solid-state fermentation, was improved by two repeated sequential exposures to ${\gamma}$-irradiation of $Co^{60}$, ultraviolet, and four repeated treatments with Nmethyl-N'-nitrosoguanidine. The mutant strain Aspergillus sp. XN15 was chosen after a rigorous screening process, with its production of the raw-starch-digesting enzyme being twice that of usual wild varieties cultured under preoptimized conditions and in an unsupplemented medium. After 17 successive subculturings, the enzyme production of the mutant was stable. Optimal conditions for the production of the enzyme by solid-state fermentation, using wheat bran as the substrate, were accomplished for the mutant Aspergillus sp. XN15. With the optimal fermentation conditions, and a solid medium supplemented with nitrogen sources of 1% urea and 1% $NH_4NO_3$, 2.5 mM $CoSO_4$, 0.05% (v/w) Tween 80, and 1% glucose, the mutant Aspergillus sp. XN15 produced the raw-starch-digesting enzyme in quantities 19.4 times greater than a typical wild variety. Finally, XN15, through simultaneous saccharification and fermentation of a raw rice corn starch slurry, produced a high level of ethanol with $Y_{p/s}$ of 0.47 g/g.

• Journal of Microbiology and Biotechnology
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• 제26권5호
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• pp.946-952
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• 2016

The eglS gene in Bacillus amyloliquefaciens encodes an endo-β-1,4-glucanase that belongs to glycosyl hydrolase family 5. In this study, a disruption mutant of gene eglS was constructed to examine its role in bacterial adaptation in plants. The mutant TB2_k, eglS gene inactivated bacterial strain, was remarkably impaired in extracellular cellulase activity. When inoculated on Brassica campestris, the TB2_k population was reduced by more than 60% compared with the wild-type strain in the root, stem, and leaf tissues. Overexpression of eglS in the wild-type strain increased the bacteria population in the plant tissues. Further studies revealed that the transcription level of eglS was correlated with bacterial population. These data demonstrate that endo-β-1,4-glucanase of B. amyloliquefaciens is required for its optimal endophytic colonization.

• Fisheries and Aquatic Sciences
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• 제14권2호
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• pp.73-78
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• 2011

Vibrio parahaemolyticus possesses two flagella systems: polar and lateral flagella for swimming in liquid and swarming on solid surfaces or in viscous environments. To elucidate the pathogenic role of these dual flagella systems, we constructed single- and double-deletion mutants of the lafA and flhAB flagellum genes and investigated their biofilm formation, cell adhesion, and colonization of the small intestine of suckling mice. The double-mutant strain was more impaired in biofilm formation than either of the single-mutant strains. In addition, the lafA, flhAB, and double-mutant strains showed 40%, 45%, and 60%, respectively, lower adherence to HeLa cells than the wild-type strain. Moreover, the lafA, flhAB, and double-mutant strains exhibited 49%, 5.6 and 6.7 times, respectively, lower colonization in a competition assay than the wild-type strain. These findings indicated that polar flagella were more important than lateral flagella for the pathogenesis of V. parahaemolyticus.