• Journal of Microbiology and Biotechnology
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• v.27 no.1
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• pp.57-66
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• 2017

Aflatoxins are classified as Group 1 (carcinogenic to humans) by the International Agency for Research on Cancer. In this study, a total of 134 fungal strains were isolated from 65 meju samples, and two fungal isolates were selected as potential aflatoxin $B_1$ ($AFB_1$)-biodetoxification fungi. These fungi were identified as Aspergillus oryzae MAO103 and A. oryzae MAO104 by sequencing the beta-tubulin gene. The two A. oryzae strains were able to degrade more than 90% of $AFB_1$ (initial concentration: $40{\mu}g/l$) in a culture broth in 14 days. The mutagenic effects of $AFB_1$ treated with A. oryzae MAO103 and MAO104 significantly decreased to 5.7% and 6.4%, respectively, in the frame-shift mutation of Ames tests using Salmonella typhimurium TA98. The base-substituting mutagenicity of $AFB_1$ was also decreased by the two fungi. Moreover, $AFB_1$ production by Aspergillus flavus was significantly decreased by the two A. oryzae strains on soybean-based agar plates. Our data suggest that the two $AFB_1$-detoxifying A. oryzae strains have potential application to control $AFB_1$ in foods and feeds.

• Korean Journal of Environmental Biology
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• v.21 no.1
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• pp.45-51
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• 2003

Genetic diversity of local populations among geologically isolated groups of Rana amurensis was refined by sequence comparison of the mitochondrial (mt) 165 rDNA genes. Each 401 base pairs of DNA sequences, which was determined from four local populations of Rana amurensis, two local populations of R. nigromacutata, and three species of the genus Rana were used in this analysis. Despite morphological similarity of Rana amurensis, Korean populations were well distinguished from the other groups on the basis of 105 rDNA gene difference. Further analyses for additional local populations belonging to R. amurensis will be necessary to clarify the taxonomic status.

• Journal of Microbiology and Biotechnology
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• v.11 no.6
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• pp.1046-1054
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• 2001

Bioleaching is the process in which insoluble metal sulfide is oxidized by specialized iron- and/or sulfur-oxidizing lithotrophic bacteria in acidic, metal-rich environments. Most of these processes are carried out by the genus Thiobacillus. Three novel Thiobacillus strains (Thiobacillus thiooxidans AZ11, Thiobacillus thiooxidans MET, and thiobacillus thiooxidans TAS) associated with bioleaching have been isolated from soil and sludge (Korean patent No. 1999-0073060 for T. thiooxidans AZ11, Korean patent No. 1999-0005798 for T. thiooxidans MET, and Korean patent No. 1999-0073059 for T. thiooxidans TAS). A partial sequence of 16S ribosomal RNA gene (16S rDNA) and the entire sequence of 16S/23S intergenic spacer region (ISR) were determined in the three above novel strains and in Thiobacillus ferrooxidans ATCC19859 as a reference strain. When phylogenetic analysis was performed based on G+C contents and sequence alignments, T. ferroxidans ATCC19859 was found to be closely related to previously registered T. ferrooxidans strains in a monophyletic manner, while the three novel T. thiooxidans strains were classified in a paraphyletic manner. Close examination on the base composition of 16S/23S ISR revealed that the 5\` part (nucleotide residues 21-200) was specific for the genus Thiobacillus. On the other end, the 3\` part (nucleotide residues 201-520) showed specificity in T. ferrooxidans strains, but not in T. thiooxidans strains. These results suggest that the proximal and distal halves of 16S/23S could be used as a genetic marker for the identification of the genus Thiobacillus and the species T. ferrooxidans, respectively.

• Journal of Microbiology and Biotechnology
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• v.12 no.3
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• pp.437-443
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• 2002

A number of soil and wastewater samples were collected from the vicinity of an effluent treatment plant for the chemical industry. Several microorganisms were screened fur their ability to decolorize the triphenylmethane group of dyes. As a result, a novel crystal violet dye-degrading strain LK-24 was isolated. Taxonomic identification including 16S rDNA sequencing and phylogenetic analysis indicated that the isolate had a $99.5\%$ homology in its 16S rDNA base sequence with Stenotrophomonas maltophilia. The triphenylmethane dye, crystal violet, was degraded extensively by growing cells of Stenotrophomonas maltophilia LK-24 in agitated liquid cultures, although their growth was strongly inhibited in the initial stage of incubation. This group of dyes is toxic, depending on the concentration used. The dye was significantly degraded at a relatively lower concentration, below $100{\mu}g\;ml^-1$, yet the growth of the cells was totally suppressed at a dye concentration of $250{\mu}g\;ml^-1$. The degradation products of crystal violet were identified as 4,4'-bis(dimethylamino)-benzophenone and ${\rho}$-dimethylaminophenol by Gas chromatography-Mass spectrometry. The 4,4'-bis(dimethylamino)-benzophenone was easily obtained in a reasonable yield, as it was not metabolized further by S. maltophilia LK-24; however, the ${\rho}$-dimethylaminophenol was not easily identifiable, as it was further metabolized.

• Journal of Microbiology and Biotechnology
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• v.25 no.11
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• pp.1801-1809
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• 2015

A phytoene synthase gene, crtB, was isolated from Kocuria gwangalliensis. The crtB with 1,092 bp full-length has a coding sequence of 948 bp and encodes a 316-amino-acids protein. The deduced amino acid sequence showed a 70.9% identity with a putative phytoene synthase from K. rhizophila. An expression plasmid, pCcrtB, containing the crtB gene was constructed, and E. coli cells containing this plasmid produced the recombinant protein of approximately 34kDa , corresponding to the molecular mass of phytoene synthase. Biosynthesis of lycopene was confirmed when the plasmid pCcrtB was co-transformed into E. coli containing pRScrtEI carrying the crtE and crtI genes encoding lycopene biosynthetic pathway enzymes. The results obtained from this study will provide a base of knowledge about the phytoene synthase of K. gwangalliensis and can be applied to the production of carotenoids in a non-carotenoidproducing host.

• Journal of Microbiology and Biotechnology
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• v.19 no.3
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• pp.250-256
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• 2009

Acinetobacter strain $KNF2022^T$ was isolated from tobacco plant roots during the screening of antiviral substances having inhibitory effects on Tobacco mosaic virus (TMV) and examined by phenotypic, chemotaxonomic, and genetic characterization. It was a nonmotile, Gram-negative bacterium. This strain contained Q-9 as the main respiratory quinone. The major cellular fatty acids of the isolate were 16:0, 18:1 w9c, and 16:1 w7c/15 iso 2OH. The DNA base composition was 44 mol%. Phylogenetic analysis based on the 16S rRNA sequence revealed that the isolate formed an evolutionary lineage distinct from other Acinetobacter species. Based on the evaluation of morphologic, physiologic, and chemotaxonomic characteristics, DNA-DNA hybridization values, and 16S rRNA sequence comparison, we propose the new species Acinetobacter antiviralis sp. nov., the type strain of which is $KNF2022^T$ (=KCTC $0699BP^T$).

• Journal of Microbiology and Biotechnology
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• v.21 no.8
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• pp.777-790
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• 2011

To elucidate the biodiversity of plant growth-promoting rhizobacteria (PGPR) in Korea, 7,638 bacteria isolated from the rhizosphere of plant species growing in many different regions were screened. A large number of PGPR were identified by testing the ability of each isolate to promote the growth of cucumber seedlings. After redundant rhizobacteria were removed via amplified rDNA restriction analysis, 90 strains were finally selected as PGPR. On the basis of 16S ribosomal RNA sequences, 68 Gram-positive (76%) and 22 Gram-negative (24%) isolates were assigned to 21 genera and 47 species. Of these genera, Bacillus (32 species) made up the largest complement, followed by Paenibacillus (19) and Pseudomonas (11). Phylogenetic analysis showed that most of the Grampositive PGPR fell into two categories: low- and high- G+C (Actinobacteria) strains. The Gram-negative PGPR were distributed in three categories: ${\alpha}$-proteobacteria, ${\beta}$- proteobacteria, and ${\gamma}$-proteobacteria. To our knowledge, this is the largest screening study designed to isolate diverse PGPR. The enlarged understanding of PGPR genetic diversity provided herein will expand the knowledge base regarding beneficial plant-microbe interactions. The outcome of this research may have a practical effect on crop production methodologies.

• Journal of Microbiology and Biotechnology
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• v.10 no.2
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• pp.258-263
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• 2000

2-Hydroxy-6-oxo-6phenylhexa-2,4-dienoate (HOPDA) hydrolase catalyzes the hydrolytic cleavage of HOPDA to bemzpate and 2-hydroxypenta-2, 4-dienoate (HPD) during microbial catabolism of biphenyl and polychlorinated biphenyls. A HOPDA hydrolase gene (pcbD) was isolated from the genomic library of Pseudomonas sp. P20 and designated as pCNUO1201; a 7.5-kb XbaI DNA fragment from Pseudomonas sp. P20 was inserted into the pBluescript SK(+) XbaI site. E. coli HB101 harboring pCNU1201 exhibited HOPDA hydrolase activity. The open reading frame (ORF) corresponding to the pcbD gene consisted of 855 base pairs with an ATG initiation codon and a TGA termination codon. The ORF was preceded by a rebosome-binding sequence of 5'-TGGAGC-3' and its G+C content was 55 mol%. The pcbD gene of Pseudomonas sp. P20 was located immedeately downstream of the pcbC gene encoding 2,3- dihydroxybiphenyl 1,2-dioxygenase, and approximately 4-kb upstream of the pcbE gene encoding HPD hydratase. The pcbK gene was able to encode a polypeptide with a molecular weight of 31,732 containing 284 amino acid residues. The deduced amino acid sequence of the HOPDA hydrolase of Pseudomonas sp. P20 exhibited high identity (62%) with those of the HOPDA hydrolases of P. putida KF715, P. pseudoalcaligenes KF707, and Burkholderia cepacia LB400, and also significant homology with those of other hydrolytic enzymes including esterase, transferase, and peptidase.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.11
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• pp.4589-4592
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• 2015

Background: Missense and frame-shift mutations within the dimer forming domain of the caspase 8 gene have been identified in several cancers. However, the genetic status of this region in precancerous lesions, like oral submucous fibrosis (OSMF), and well differentiated oral squamous cell carcinomas (OSCCs) in patients from southern region of India is not known, and hence the present study was designed to address this issue. Materials and Methods: Genomic DNA isolated from biopsy tissues of thirty one oral submucous fibrosis and twenty five OSCC samples were subjected to PCR amplification with intronic primers flanking exon 7 of the caspase 8 gene. The PCR amplicons were subsequently subjected to direct sequencing to elucidate the status of mutation. Results: Sequence analysis identified a frame-shift and a novel missense mutation in two out of twenty five OSCC samples. The frame-shift mutation was due to a two base pair deletion (c.1225_1226delTG), while the missense mutation was due to substitution of wild type cysteine residue with phenylalanine at codon 426 (C426F). The missense mutation, however, was found to be heterozygous as the wild type C426C codon was also present. None of the OSMF samples carried mutations. Conclusions: The identification of mutations in OSCC lesions but not OSMF suggests that dimer forming domain mutations in caspase 8 may be limited to malignant lesions. The absence of mutations in OSMF also suggests that the samples analyzed in the present study may not have acquired transforming potential. To the best of our knowledge this is the first study to have explored and identified frame-shift and novel missense mutations in OSCC tissue samples.

• Journal of fish pathology
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• v.7 no.2
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• pp.105-112
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• 1994

A new bacterial infection occurred among the cultured Korean catfish, Silurus asotus, in Chunbuk prefecture, Korea, 1993. This disease produced about 30% mortality in the fish for 4 months. The diseased fish was swimming listless at the water surface with head up and tail down, sometimes spinnig in circles. The most outstanding clinical sign was ulceration on the skull and at the base of the pectoral fins. The causative organism was isolated from the brain, kidney, spleen and liver of diseased fish, and identified as Edwardsiella icaluri by the biochemical and biophysical characteristics. After intraperitoneal innoculaton of the isolate, the pathogenicity was proved positive for Korean catfish, S. asotus, and channel catfish, Ictalurus punctatus, but negative for carp, Cyprinus carpio.