• Microbiology and Biotechnology Letters
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• v.19 no.5
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• pp.429-432
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• 1991

In order to prepare probiotics, a strain which has resistant against acid, bile salts and antibiotics was isolated from infant and anirnat feces. Among these isolated strains, TK- 19 showed a strong acid tolerance and growth at 500 $\mu g$/ml of Na-deoxycholate. Also strain TK-19 was resistant to kanarnycin (30 $\mu g$/ml), streptomycin (10 $\mu g$/ml), nisin (50 $\mu g$/ml) and tetracycline (10 $\mu g$/ml). The isolated strain TK-19 was identified as Streptococcus faeciam, and was named Streptococcus faeciurn TK-19.

• Proceedings of the Korean Biophysical Society Conference
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• 2001.06a
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• pp.42-42
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• 2001

Candida albicans possess cyanide-resistant respiratory pathway, which is mediated by alternative oxidase. The activity of alternative oxidase has been found to be dependent on several regulatory mechanisms. In order to investigate the influence of D-erythroascorbic acid on respiration of C. albicans, the respiratory activity of the cells was measured with oxygen monitor. ALO1 is known to encode D-arabinono-1,4-lactone oxidase that catalyses the final step of D-erythroascorbic acid biosynthesis in C. albicans.(omitted)

• Food Science of Animal Resources
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• v.30 no.4
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• pp.634-640
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• 2010

The principal objective of this study was to screen and select acid-tolerant Lactobacillus strains from chicken feces, feeds, and other sources. Fourty six strains evidencing acid tolerance (pH 3.5) were isolated in this study. Among them, nine strains exhibited marked immunostimulatory effects. Therefore, nine candidate strains were characterized for probiotic use. In order to evaluate macrophage activation, NO production was measured using RAW 264.7 cells. In particular, three strains (FC812, FC222, and FC113) evidenced the highest levels of NO production measured at $38.39{\pm}20.01,\;35.06{\pm}27.73$, and $33.88{\pm}15.99{\mu}M$, respectively, at a concentration of $10^{8}CFU/mL$. The majority of strains, with the exception of strain FC322, evidenced marked resistance to artificial gastric juice (pH 2.5 with 1%(w/v) pepsin). Additionally, strains FC222, FC421, FC511, and FC721 were highly resistant to artificial bile acid (0.1%(w/v) oxgall), whereas strains FC113, FC322, FC422, FC621, and FC812 were the least resistant to bile. All nine strains exerted antimicrobial effects against chickenrelated pathogens. Additionally, all nine strains were found to be resistant to several antibiotics. The isolated strains, except for strain FC322, were tentatively identified as Lactobacillus salivarius, using an API 50 CHL kit. These results demonstrate that some probiotic organisms may potentially probiotic properties, and thus may serve as an effective alternative to antibiotics in animal applications.

• Korean Journal of Veterinary Service
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• v.42 no.3
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• pp.153-159
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• 2019

The objective of this study was to identify mutations in the quinolone resistance determining region (QRDR) of the gyrA, gyrB, parC and parE genes, and the presence of plasmid-mediated quinolone resistance (PMQR) genes: qnrA, qnrB, qnrS, aac(6')-lb-cr and qepA in 40 nalidixic acid- resistant ($NA^R$) Salmonella isolates isolated from poultry slaughterhouse. The MIC of NA and ciprofloxacin for 40 $NA^R$ Salmonella isolates was $128{\sim}512{\mu}g/mL$ and < $0.125{\sim}0.25{\mu}g/mL$, respectively. The Salmonella isolates were resistant to NA (100%), gentamicin (5.0%) and ampicillin (2.5%). All $NA^R$ Salmonella isolates represented point mutation in codons Aspartic acid(Asp)-87 (90%) and Serine(Ser)-83 (10%) of QRDR of gyrA gene: $Asp87{\rightarrow}glycine$, $Ser83{\rightarrow}tyrosine$. No mutations were observed in QRDR of the gyrB, parC and parE gene. Moreover PMQR genes was not found in any of the tested isolates. Our findings showed that DNA gyrase is the primary target of quinolone resistance and a single mutation in codon Asp87 and Ser83 of the gyrA gene can confer resistance to NA and reduced susceptibility ciprofloxacin in Salmonella isolates.

• Korean Journal of Environmental Agriculture
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• v.14 no.3
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• pp.319-328
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• 1995

This study was carried out to investigate the resistance mechanism by three different kinds of procymidone-resistant and susceptible isolates of Botrytis cinerea which had been collected from green houses. The average resistance level of the resistant strains was 1,000 times higher than that of susceptible ones. Also, it was revealed that the resistance was not originated from components excreted by Botrytis cinerea, based on the result obtained from the treatment with piperonyl butoxide and triphenyl phosphate as an inhibitor of monooxygenase and esterase, respectively. The total lipod content of resistant strains was 1.3 times higher than that of susceptible ones, among fatty acids, palmitic acid, stearic acid, and linoleic and being 3.0, 2.5, and 2.0 times higher, respectinely. Also slight differences in sterol contents and components were observed. The crude chitin content was slightly higher in susceptible strains but contents of N-acetyl glucosamine, a hydrolysate of chitin, were about 2 times higher in resistant ones.

• Microbiology and Biotechnology Letters
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• v.26 no.1
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• pp.45-49
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• 1998

Two kinds of Mutants of Corynebacterium glutamicum, which were resistant to branched chain amino acid analogues, were obtained for L-leucine production; C. glutamicum LT26 resistant to 4-azaleucine and $\alpha$-amino-$eta$-hydroxyvaleric acid, and from which C. glutamicum LT3811-70 resistant to DL-4-thiaisoleucine were derived. Accumulation of L-leucine in the culture broths of these mutant strains, C. glutamicum LT26 and LT3811-70, were much higher than those of their parent strains even though they were non-auxotrophic mutants. Enzymatic analyses were performed to measure the activities of $\alpha$-acetohydroxy acid synthase (AHAS) and $\alpha$-isopropylmalate synthase (IPMS), which were the key enzymes for the L-isoleucine, L-valine and L-leucine biosynthetic pathways branching from a common precursor. In C. glutamicum LT26 and LT3811-70, AHAS and IPMS were found to be derepressed and desensitized to L-leucine. In addition, in C. glutamicum LT3811-70, IPMS was further more derepressed by L-leucine and AHAS was more desensitized by L-isoleucine and L-valine compared to its parent strain, C. gIEitamicum LT26.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.98-104
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• 2023

Effective and alternative strategies to control methicillin-resistant Staphylococcus aureus (MRSA) are consistently needed. Previous study presented that 7,10-epoxy-octadeca-7,9-dienoic acid (EODA) was produced from 7,10-dihydroxy-8(E)-octadecenoic acid through one-step heat treatment. Further studies confirmed that EODA was highly active against broad range of pathogenic bacteria including MRSA, promising development of a novel antibacterial agent to control MRSA. However, there are some practical huddles for industrialization of EODA, especially high cost for fine purification. To address this problem, this study was focused on determination of any changes in the antibacterial activities of EODA when used as a crude extract. As a result, any significant changes in the antibacterial activities of EODA was not detected and additional synergistic effect for commercial antibiotics on antibacterial activity was sustained as it was.

• Journal of Korean Society of Forest Science
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• v.88 no.1
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• pp.31-37
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• 1999

The frequency of gall formation by pine needle gall midges ranged from 35% to 40% in both P. densiflora and P. thunbergii species. However, there was no indication of gall development from larva on both P. virgiana and P. rigida species suggesting that some specific compounds might play role in preventing gall formation of larva. The susceptible species to pine needle gall midges including P. densiflora and P. thunbergii contained a little salicylic acid under the free phenolic compound conditions while the resistant species against such insects including P. virginiana and P. rigida species contained about 37ppm to 50ppm of salicylic acid. Thus, this compound might have important roles in insect resistance. The contents of internal salicylic acid in the needles of susceptible pines increased from 9.5ppm to 20.6ppm after direct external irrigation of salicylic acid solution and flour treatment on roots. As a result, the frequency of gall formation decreased dramatically 17~19 times lower when compared with that of control. According to our results, the application of salicylic acid for effective prevention against insect damages should be performed before hatching eggs. The frequency of gall formation in the hybrid pines of P. thunbergii(susceptible) and P. virginiana(resistant) showed approximately 24% as average value of those in both species. In the case of specific individuals, it ranged from 2.8% to 11.5% in hybrids of both species. Therefore, effective production of insect resistant pines can be obtained through hybrids by crossing between susceptible and resistant species including P. thunbergii and P. virginiana by increasing internal salicylic acid contents of the needles.

• The Plant Pathology Journal
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• v.22 no.4
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• pp.369-374
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• 2006

To characterize benzimidazole-resistant and -sensitive Monilinia fructicola populations, the fungal isolates were obtained from peach plants showing brown rot and bloosom blight. Benzimidazole-sensitive isolates did not grow on potato dextrose agar(PDA) amended with $\geq1.0{\mu}g$ active ingredient(a.i.)/ml of the fungicides. However, benzimidazole-resistant isolates grew on PDA regardless of the tested concentrations of fungicides. Benzimidazole-resistant isolates did not grow on diethofencarb-PDA, but sensitive isolates grew on the same PDA. In the nucleotide sequences of $\beta$-tubulin gene, only codon 198(GAG: glutamic acid), a target site for benzimidazole, was replaced with GCG(alanine) in all of the resistant isolates, and this substitution seems to play an important role in the development of resistance. Other interesting codons such as 165(GCT), 200(TTC), and 241(GCT) were not changed among the isolates. Benzimidazole-resistant and -sensitive isolates were clustered clearly in random amplified polymerphic DNA analyses and the results revealed that low levels of genetic diversity between benzimidazole-sensitive and -resistant isolates of M. fructicola in the investigated regions.

• Journal of Microbiology and Biotechnology
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• v.26 no.9
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• pp.1620-1628
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• 2016

In this study, we investigated colistin resistance mechanisms associated with the regulation of the pbgP operon in Klebsiella pneumoniae, using four isogenic pairs of colistin-susceptible strains and their colistin-resistant derivatives and two colistin-resistant clinical isolates. Amino acid sequence alterations of PhoPQ, PmrAB, and MgrB were investigated, and mRNA expression levels of phoQ, pmrB, pmrD, and pbgP were measured using quantitative real-time PCR. The phoQ and pmrB genes were deleted from two colistin-resistant derivatives, 134R and 063R. We found that phoQ, pmrD, and pbgP were significantly upregulated in all colistin-resistant derivatives. However, pmrB was significantly upregulated in only two colistin-resistant derivatives and one clinical strain. pmrB was not overexpressed in the other strains. The minimum inhibitory concentration of colistin was drastically lower in both phoQ- and pmrB-deleted mutants from a colistin-resistant derivative (134R) that was overexpressing phoQ and pmrB. However, colistin susceptibility was restored only in a phoQ-deleted mutant from a colistin-resistant derivative (063R) without overexpression of pmrB. In conclusion, two different regulations of the pbgP operon may associate with the development of colistinresisant K. pneumoniae.