• Research in Plant Disease
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• v.24 no.2
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• pp.138-144
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• 2018

In December 2016, stem rot symptoms were observed on Persian buttercup (Ranunculus asiaticus) plants in Chilgok, Gyeongbuk, Korea. In the early stage of the disease, several black spots appeared on the stem of infected plants. As the disease progressed, the infected stem cleaved and wilted. The causal agent was isolated from a lesion and incubated on Reasoner's 2A (R2A) agar at $25^{\circ}C$. Total genomic DNA was extracted for phylogenetic analysis. Based on the 16S rRNA gene analysis, the isolated strain was found to belong to the genus Pseudomonas. To identify the isolated bacterial strain at the species level, the nucleotide sequences of the gyrase B (gyrB) and RNA polymerase D (rpoD) genes were obtained and compared with the sequences in the GenBank database. As the result, the causal agent of the stem rot disease was identified as Pseudomonas marginalis. To determine the pathogenicity of the isolated bacterial strain, it was inoculated into the stem of healthy R. asiaticus plant, the inoculated plant showed a lesion with the same characteristics as the naturally infected plant. Based on these results, this is the first report of bacterial stem rot on R. asiaticus caused by P. marginalis in Korea.

• Journal of Microbiology and Biotechnology
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• v.20 no.12
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• pp.1735-1743
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• 2010

The full-length genes gyrB (2,415 bp), parC (2,277 bp), and parE (1,896 bp) in Edwardsiella tarda were cloned by PCR with degenerate primers based on the sequence of the respective quinolone resistance-determining region (QRDR), followed by elongation of 5' and 3' ends using cassette ligation-mediated PCR (CLMP). Analysis of the cloned genes revealed open reading frames (ORFs) encoding proteins of 804 (GyrB), 758 (ParC), and 631 (ParE) amino acids with conserved gyrase/topoisomerase features and motifs important for enzymatic function. The ORFs were preceded by putative promoters, ribosome binding sites, and inverted repeats with the potential to form cruciform structures for binding of DNA-binding proteins. When comparing the deduced amino acid sequences of E. tarda GyrB, ParC, and ParE with those of the corresponding proteins in other bacteria, they were found to be most closely related to Escherichia coli GyrB (87.6% identity), Klebsiella pneumoniae ParC (78.8% identity), and Salmonella Typhimurium ParE (89.5% identity), respectively. The two topoisomerase genes, parC and parE, were found to be contiguous on the E. tarda chromosome. All 18 quinolone-resistant isolates obtained from Korea thus far did not contain subunit alternations apart from a substitution in GyrA (Ser83$\rightarrow$Arg). However, an alteration in the QRDR of ParC (Ser84$\rightarrow$Ile) following an amino acid substitution in GyrA (Asp87$\rightarrow$Gly) was detected in E. tarda mutants selected in vitro at $8{\mu}g/ml$ ciprofloxacin (CIP). A mutant with a GyrB (Ser464$\rightarrow$Leu) and GyrA (Asp87$\rightarrow$Gly) substitution did not show a significant increase in the minimum inhibitory concentration (MIC) of CIP. None of the in vitro mutants exhibited mutations in parE. Thus, gyrA and parC should be considered to be the primary and secondary targets, respectively, of quinolones in E. tarda.

• Journal of Microbiology
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• v.44 no.6
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• pp.591-599
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• 2006

To address the diversity of cyclodextrin-producing P. graminis strains isolated from wheat roots and rhizospheres of maize and sorghum sown in Australia, Brazil, and France, restriction fragment length polymorphism analysis of part of genes encoding RNA polymerase (rpoB-RFLP) and DNA gyrase subunit B (gyrB-RFLP) was used to produce genetic fingerprints. A phylogenetic tree based on rpoB gene sequences was also constructed. The isolates originated from Brazil could be separated from those from Australia and France, when data from the rpoB-based phylogenetic tree or gyrB-RFLP were considered. These analyses also allowed the separation of all P. graminis strains studied here into four clusters; one group formed by the strains GJK201 and $RSA19^T$, second group formed by the strains MC22.02 and MC04.21, third group formed by the strains TOD61, TOD 221, TOD302, and TOD111, and forth group formed by all strains isolated from plants sown in Cerrado soil, Brazil. As this last group was formed by strains isolated from sorghum and maize sown in the same soil (Cerrado) in Brazil, our results suggest that the diversity of these P. graminis strains is more affected by the soil type than the plant from where they have been isolated.

• Journal of fish pathology
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• v.33 no.2
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• pp.111-118
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• 2020

The genus Edwardsiella belonging to the family Enterobacteriaceae is a member of Gram-negative rod-shaped bacteria that cause disease in diverse aquatic organisms such as fish, amphibians and reptiles as well as avians and mammals including human throughout the world. This genus had been composed of three species, E. hoshinae, E. ictaluri and E. tarda, but recent researches erected two novel species, E. anguillarum and E. piscicida that were conventionally identified as E. tarda. In this study, we isolated seven strains belonging to the genus Edwardsiella from freshwater fishes that had been reared at inland fish farms in South Korea and investigated their biochemical characteristics and molecular phylogenetic relationships. The seven strains showed typical characteristics of four Edwardsiella species, E. anguillarum, E. ictaluri, E. piscicida and E. tarda, by biochemical analyses of Gram staining, indole and hydrogen sulfide (H2S) production, and API (Analytic Profile Index) 20E test. Molecular phylogenetic analyses inferred from DNA sequence data of both 16S ribosomal RNA (rRNA) and DNA gyrase subunit B (gyrB) genes were congruent with the biochemical characteristics. As a result, both biochemical and molecular phylogenetic analyses identified four strains isolated from three Anguilla species as E. anguillarum, E. piscicida and E. tarda, two strains from Pelteobagrus fulvidraco and Silurus asotus as E. ictaluri, and one strain from Moroco oxycephalus as E. piscicida. In this study, we isolated and successfully identified recently newly erected species, E. anguillarum and E. piscicida in addition to historically notorious pathogenic species, E. ictaluri and E. tarda. In the future study, systematic and comprehensive monitoring of the four Edwardsiella species are required for studying differences in pathogenicity among freshwater fishes.