• 대한수의학회지
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• 제44권4호
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• pp.571-579
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• 2004

In order to obtain the genetic informations of the Korean isolates of porcine circovirus 2 (PCV2), nucleotide sequences of total genome of three isolates and open reading frame 2 (ORF2) of four isolates were determined and compared with those of other reference PCV2 isolates. Nucleotide sequences of 3 isolates showed over 99% homology with those of reference strain (GenBank accession no. AF027217). Point mutations were mainly determined on ORF2 regions but little on ORF1 regions. The patterns of pointmutated sites and nucleotide substitution on ORF2 regions were generally consistent between Korean isolates, and these mutated sites observed in Korean isolates were also relatively similar to those of foreign isolates. Phylogenetic analysis of nucleotide or amino acid sequences showed that there were minor branches consisting of three clusters; cluster of Korea, Canada and America, cluster of Spain and Taiwan, and the last cluster of French and China isolates. These results suggested that Korean PCV2s were probably originated from North America such as Canada or USA. The genetic informations obtained from this study could be useful for the research of diagnosis and pathogenecity of PCV2.

• The Plant Pathology Journal
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• 제35권1호
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• pp.84-89
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• 2019

Two-component systems (TCSs) are critical to the pathogenesis of Xanthomonas oryzae pv. oryzae (Xoo). We mutated 55 of 62 genes annotated as responsive regulators (RRs) of TCSs in the genome of Xoo strain PXO99A and identified 9 genes involved in Xoo virulence. Four (rpfG, hrpG, stoS, and detR) of the 9 genes were previously reported as key regulators of Xoo virulence and the other 5 have not been characterized. Lesion lengths on rice leaves inoculated with the mutants were shorter than those of the wild type and were significantly restored with gene complementation. The population density of the 5 mutants in planta was smaller than that of PXO99A at 14 days after inoculation, but the growth curves of the mutants in rich medium were similar to those of the wild type. These newly reported RR genes will facilitate studies on the function of TCSs and of the integrated regulation of TCSs for Xoo pathogenesis.

• 한국버섯학회지
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• 제18권4호
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• pp.393-397
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• 2020

Mycelium composites and leathers have versatile material properties based on their composition and manufacturing process. To prepare mycelium mat for the production of mushroom leather, several strains were mutated by gamma rays. Some mutant strains, including Lentinula edodes, Ganoderma lucidium, and Schizophyllum commune showed good hyphae growth rate and density on saw-dust media. Irradiation power (Gy), time, and height from the radiation source to the sample were examined. Based on the preliminary data obtained in this study, comprehensive research should be conducted to explore the optimal strains and culture conditions for mycelium-based leather production.

• Journal of Microbiology and Biotechnology
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• 제14권6호
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• pp.1324-1326
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• 2004

In previous studies, we isolated an isogenic LPS mutant of Bradyrhizobium japonicum 61A101C, which was completely devoid of O-polysaccharide and had altered cell surface characteristics. Subsequently, the mutated gene was identified, cloned, and used to complement the LPS mutant strain JS314 to restore the phenotype. Since it has been reported that in Escherichia coli LPS O-polysaccharide is involved in resistance to an organic acid such as acetic acid under low pH (Barna et al., Molecular Microbiology 43: 629-640, 2002), we compared the organic acid resistance of the three B. japonicum strains; wild-type 61A101C, the LPS mutant JS314, and the complemented strain to determine whether the role of O-polysaccharide in the resistance to organic acid could be generalized. Growth of all three strains was inhibited by the presence of 3 mM acetic acid under acidic condition (pH 5.5). To our surprise, however, in the presence of 2 mM acetic acid, wild-type and the complemented strains did not grow while the $LPS^-$ mutant showed a significant growth. Therefore, unlike in E. coli, the lack of O­polysaccharide of LPS appears to render B. japonicum more resistant to organic acid.

• Journal of Microbiology and Biotechnology
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• 제27권1호
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• pp.101-111
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• 2017

The task of improving a fungal strain is highly time-consuming due to the requirement of a large number of flasks in order to obtain a library with enough diversity. In addition, fermentations (particularly those for fungal cells) are typically performed in high-volume (100-250 ml) shake-flasks. In this study, for large and rapid screening of itaconic acid (IA) high-yielding mutants of Aspergillus terreus, a miniaturized culture method was developed using 12-well and 24-well microtiter plates (MTPs, working volume = 1-2 ml). These miniaturized MTP fermentations were successful, only when highly filamentous forms were induced in the growth cultures. Under these conditions, loose-pelleted morphologies of optimum sizes (less than 0.5 mm in diameter) were casually induced in the MTP production cultures, which turned out to be the prerequisite for the active IA biosynthesis by the mutated strains in the miniaturized fermentations. Another crucial factor for successful MTP fermentation was to supply an optimal amount of dissolved oxygen into the fermentation broth through increasing the agitation speed (240 rpm) and reducing the working volume (1 ml) of each 24-well microtiter plate. Notably, almost identical fermentation physiologies resulted in the 250 ml shake-flasks, as well as in the 12-well and 24-well MTP cultures conducted under the respective optimum conditions, as expressed in terms of the distribution of IA productivity of each mutant. These results reveal that MTP cultures could be considered as viable alternatives for the labor-intensive shake-flask fermentations even for filamentous fungal cells, leading to the rapid development of IA high-yield mutant strains.

• The Plant Pathology Journal
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• 제17권3호
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• pp.174-179
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• 2001

The plant growth-promoting Pseudomonas strains, WR8-3 (Pseudomonas fluorescens), WR9-11 (Pseudomonas sp.) and WR9-16 (P.putida), which induced resistance systematically in watermelon to gummy stem rot were investigated on their induced systemic resistance(ISR)-related characteristics. The pyoverdine production was repressed in the standard succinate medium by increasing the concentration of $\textrm{FeCL}_3$. But the iron-binding ability on chrome azurol S agar media (CAS) was observed only in the strains, WR8-3 and WR9-16. When the two strains were mutated, the resulting iron-binding siderophore-negative mutants, WR8-3m and WR 9-16m, failed to promote the growth of watermelon and to induce resistance. The strains, WR8-3 and WR 9-16, slightly inhibited the growth of Didymella bryoniae at a low concentration of $\textrm{FeCL}_3$ on Kong's medium B, but not to exert control dffect. The strain WR9-11 showed antagonism in the concentration of $\textrm{FeCL}_3$ from 0 to $1,000\mu\textrm{M}$. When the crude lipoplysaccharide of each strain was treated in the rhizosphere of watermelon, mean lesion area was similar to that of the untreated control. The strains, WR9-11 and WR9-16 produced some level of hydrogen cyanide (HCN). Salicylic acid production was not detected in all of the strains.

• 한국식품과학회지
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• 제43권3호
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• pp.396-400
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• 2011

We examined the in vitro mutagenic and antimutagenic effects of hexane-extracted hemp (Cannabis sativa L. subsp. sativa var. sativa) seed oil (HO) with and without S9-mediated metabolic activation, using the TA98 and TA100 Salmonella Typhimurium strains. The MTT assay revealed no cytotoxicity in HepG2 cells for HO quantities $\leq400g$/mL. In the mutagenicity test, revertant colonies did not exceed spontaneous colonies in number. Colony numbers did not increase in either strain after HO treatment, with or without metabolic activation. HO showed no mutagenic effects and did not induce a mutation in either strain. In the antimutagenicity test, HO reduced the number of mutated colonies induced by 4NQO in both strains. The inhibition rates of HO (TA98, 21-91%; TA100, 21-85%) indicated a potent reduction in mutagenicity induced by 4NQO. HO showed no significant mutagenicity and may have antimutagenic effects, as assessed by Ames testing.

• 한국식품과학회지
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• 제32권2호
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• pp.424-430
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• 2000

김치발효에 관여하는 균종들에 대해 항균작용이 있는 것으로 알려진 adipic acid를 김치제조시 첨가하고, 동시에 adipic acid 저항성 변이균주인 Leuconostoc mesenteroides와 Leu. paramesenteroides 두 균주를 김치에 starter로서 첨가하여 발효시키므로써 김치의 저장기간 연장과 풍미증진 효과를 조사하였다. 또한 이를 위한 변이균주의 최적의 첨가량을 조사하였다. 김치발효의 주요 숙성균주로서 산에 약한 Leu. mesenteroides와 Leu. paramesenteroides 두 균주를 adipic acid에 대한 저항성을 갖도록 변이시킨 후 adipic acid 0.16%와 함께 두 변이주를 각각 단독으로 또는 두 변이균주의 혼합균주(1 : 10)로서 김치제조시 starter로 첨가한 경우. 단독첨가 보다는 혼합균주인 경우가 산패지연 효과와 관능특성 면에서 우수하였으며 혼합균주의 최적 첨가량은 0.005%로 조사되었다.

• 한국동물위생학회지
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• 제44권2호
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• pp.73-83
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• 2021

Although many swine farms continuously vaccinated to sow to prevent Porcine epidemic diarrhea(PED), PED has occurred annually in swine herds in Jeonbuk province, Korea. In the present study, the small intestine and feces samples from 17 farms where severe watery diarrhea and death of newborn piglets occurred in 2019 were collected, amplified by RT-PCR and determined the complete nucleotide sequences of the spike (S) glycoprotein genes of nine Jeonbuk PEDV isolates. The spike (S) glycoprotein is an important determinant for molecular characterization and genetic relationship of PEDV. These nine complete S gene isolates were compared with other PEDV reference strains to identify the molecular diversity, phylogenetic relationships and antigenicity analysis. 9 field strains share 98.5~100% homologies with each other at the nucleotide sequence level and 97.3~100% homologies with each other at the amino acid level. The nine Jeonbuk PEDV isolates were classified into G2b group including a genetic specific signal, S-indels (insertion and deletion of S gene). In addition, comparisons the neutralizing epitopes of S gene between 9 field strains and domestic vaccine strains of Korea mutated 12-15 amino acids with SM-98-1 (G1a group) and mutated 0-3 amino acids with QIAP1401 (G2b group). Therefore, the development of G2b-based live vaccines will have to be expedited to ensure effective prevention of endemic PED in Korea. In addition, we will need to be prepared with periodic updates of preventive vaccines based on the PEDV variants for the re-emergence of a virulent strain.

• 한국미생물·생명공학회지
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• 제34권2호
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• pp.136-142
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• 2006

Haematococcus pluvialis는 astaxanthin을 많이 생산하는 미세조류로써 astaxanthin은 항산화제로 면역반응을 강화시켜주며 항암효과 등을 가지고 있다. 그런데 야생종의 낮은 생장속도와 astaxanthin의 생산에는 한계가 있기 때문에 이를 극복하기위해 돌연변이 방법을 사용하였다. 돌연변이 방법으로는 자외선 조사와 EMS와 colchicines 처리를 사용하여 야생종보다 colony가 크고 더 붉은 것은 선택하였다. 선별된 돌연변이들은 carotenoid 생합성과정을 억제하는 nicotine 과 diphenylamine을 이용하여 다시 선별하였다. 그때 생존율은 40-50%이었고 여기서 선별된 균주들을 다시 규모를 키워 배양한 결과 자외선 처리한 돌연변이인 U15-5가 야생종보다 세포당 total carotenold 생산량이 1.68배 증가하였고, colchicine 처리한 DS와 M4-3은 생장속도가 $20\sim30%$ 증가하였다.