Biomedical subjects

Kyoung-Ho Kim

Publications and source records attributed to Kyoung-Ho Kim.

8 recordsLinked to original sources

PubMed2006

Bacteroides fragilis enterotoxin induces cyclooxygenase-2 and fluid secretion in intestinal epithelial cells through NF-kappaB activation.

Bacteroides fragilis produces an approximately 20-kDa heat-labile toxin (B. fragilis enterotoxin, BFT) which is known to be associated with diarrhea. To determine whether cyclooxygenase (COX)-2, via NF-kappaB activation, can contribute to BFT-induced diarrhea, the relationship between COX-2 expression and fluid secretion in BFT-stimulated human intestinal epithelial cells was examined. BFT stimulation increased the expression of COX-2, but not COX-1, in human intestinal epithelial cells. Suppression of the NF-kappaB signal significantly decreased COX-2 expression in response to BFT stimulation. Prostaglandin E2 (PGE2) levels were increased in parallel with COX-2 expression, and, conversely, PGE2 production was significantly inhibited when COX-2 or NF-kappaB activities were suppressed using COX-2 small interfering RNA (siRNA), p65 NF-kappaB subunit siRNA, or a retrovirus encoding the IkappaBalpha superrepressor. In addition, a selective COX-2 inhibitor, NS-398, significantly inhibited the increased cAMP level induced by BFT stimulation. Furthermore, a selective COX-2 inhibitor prevented BFT-induced PGE2 production and ileal fluid secretion in a mouse ileal loop model. These results suggest that the secretory response to BFT stimulation may be mediated by the production of PGE2, through NF-kappaB activation and the up-regulation of COX-2 in intestinal epithelial cells.

Animals↗

PubMed2006

Stappia marina sp. nov., a marine bacterium isolated from the Yellow Sea.

A Gram-negative, aerobic and halophilic bacterium designated strain mano18T was isolated from a tidal flat area of Dae-Chun, Chung-Nam, Korea. This strain was motile by means of polar flagella, occasionally forming rosette-like aggregates, reduced nitrate to nitrite, required sodium ions for growth, exhibited catalase and oxidase activities and contained Q-10 as the major quinone and C(18 : 1)omega7c as the dominant cellular fatty acid. Analysis of the 16S rRNA gene sequence revealed that this strain is affiliated with a cluster within the Alphaproteobacteria. Strain mano18T synthesized bacteriochlorophyll under aerobic conditions. The 16S rRNA gene sequence similarity between strain mano18T and the most closely related species, Stappia aggregata DSM 13394T, was 98.5 %. Levels of DNA-DNA relatedness between strain mano18T and the type strains of S. aggregata and Stappia stellulata were respectively 6.2-11.2 and 3.3-7.6 %. Strain mano18T, like other Stappia strains, possesses carbon monoxide dehydrogenase genes. The results of DNA-DNA hybridization and the polyphasic data confirmed that strain mano18T can be considered to represent a novel taxon in the genus Stappia. The name Stappia marina sp. nov. is proposed for the tidal flat isolate; the type strain is strain mano18T (= KCTC 12288T = DSM 17023T).

Aldehyde Oxidoreductases↗

PubMed2006

Lactobacillus siliginis sp. nov., isolated from wheat sourdough in South Korea.

The taxonomic position of two lactic-acid-producing bacterial strains, isolated from wheat sourdough in South Korea, was studied using a polyphasic approach. Phylogenetic analysis on the basis of 16S rRNA gene sequences and biochemical and physiological characteristics indicated these two strains to be members of the genus Lactobacillus. They had high 16S rRNA gene sequence similarity (98.5 %) with Lactobacillus rossiae DSM 15814(T) and very low (<94.0 %) similarity with any other recognized species of the genus Lactobacillus. These two strains (designated M1-212(T) and M2-236) were heterofermentative, facultatively anaerobic, Gram-positive, non-spore-forming, non-motile, short rod-shaped bacteria. The optimum growth temperature for these strains was 30 degrees C (no growth at 15 or 45 degrees C) and they were able to tolerate 5 % (w/v) NaCl. The G+C content of the genomic DNA of the two strains was 45.5 mol%, within the range of values reported for the genus Lactobacillus (32-53 mol%). The peptidoglycan was of the A3alpha (l-lys-d-glu-l-Ala) type. Physiological, biochemical and genotypic data, as well as results of DNA-DNA hybridization of the genomic DNA with one of the closest phylogenetic relatives, L. rossiae DSM 15814(T), indicated that the strains represent a novel species of the genus Lactobacillus, for which the name Lactobacillus siliginis sp. nov. is proposed. The type strain is M1-212(T) (=KCTC 3985(T)=NBRC 101315(T)).

Base Composition↗

PubMed2006

Sphingobacterium daejeonense sp. nov., isolated from a compost sample.

A Gram-negative, strictly aerobic, rod-shaped, non-motile, non-spore-forming bacterial strain, designated TR6-04(T), was isolated from compost and characterized taxonomically by using a polyphasic approach. The organism grew optimally at 30 degrees Celsius and at pH 6.5-7.0. The isolate was positive for catalase and oxidase tests but negative for gelatinase, indole and H(2)S production. Comparative 16S rRNA gene sequence analysis showed that strain TR6-04(T) fell within the radiation of the cluster comprising Sphingobacterium species and clustered with Sphingobacterium mizutaii ATCC 33299(T) (96.7 % sequence similarity); the similarity to sequences of other species within the family Sphingobacteriaceae was less than 92.0 %. The G+C content of the genomic DNA was 38.7 mol%. The predominant respiratory quinone was MK-7. The major fatty acids were iso-C(15 : 0), iso-C(17 : 0) 3-OH and summed feature 4 (iso-C(15 : 0) 2-OH and/or C(16 : 1)omega7c). These chemotaxonomic data supported the affiliation of strain TR6-04(T) to the genus Sphingobacterium. However, on the basis of its phenotypic properties and phylogenetic distinctiveness, strain TR6-04(T) (=KCTC 12579(T)=LMG 23402(T)=CCUG 52468(T)) should be classified as the type strain of a novel species, for which the name Sphingobacterium daejeonense sp. nov. is proposed.

Bacterial Typing Techniques↗

PubMed2005

Mitogen-activated protein kinase and activator protein-1 dependent signals are essential for Bacteroides fragilis enterotoxin-induced enteritis.

The approximately 20-kDa heat-labile toxin produced by enterotoxigenic Bacteroides fragilis is known to be associated with the development of enteritis. However, the molecular mechanism involved is not yet fully understood. In this study, we assessed whether B. fragilis enterotoxin (BFT)-induced enteritis is related to mitogen-activated protein kinase (MAPK) signaling pathways. In human colon epithelial cells, BFT activated three major MAPK cascades. The activation of p38 was sustained for a relatively long period, while the stimulation of extracellular signal-regulated kinases (ERK) and c-Jun N-terminal kinase (JNK) was transient. BFT stimulation also activated AP-1 signals composed of c-Jun/c-Fos heterodimers. The p38 inhibitor SB203580 and the ERK inhibitor U0126 reduced not only AP-1 activity, but also decreased IL-8 and MCP-1 expression. In addition, the overexpression of superrepressors for c-Jun and Ras induced by BFT stimulation decreased the levels of IL-8 and MCP-1 production. Furthermore, SB203580 prevented BFT-induced colitis in the mouse ileum, as evidenced by significant decreases in villous destruction, neutrophil infiltration, and mucosal congestion. These results suggest that a pathway, including Ras, MAPK, and subsequent AP-1 activation, is required for IL-8 and MCP-1 expression in intestinal epithelial cells exposed to BFT, and can be involved in the development of enteritis.

Animals↗

PubMed2004

Hydrogeochemistry of alluvial groundwaters in an agricultural area: an implication for groundwater contamination susceptibility.

Alluvial groundwaters in the area where intensive agricultural activity takes place were geochemically investigated to evaluate factors regulating groundwater quality of alluvial aquifers. For this study, 55 groundwater samples were taken from the uniformly distributed irrigation wells and were classified into three distinct groups according to their geochemical characteristics. This study reveals that the groundwater quality and the geochemical characteristics of the clustered groups are consistent with the geology of the area. The samples collected from the area where a thick silt bed overlies the sand aquifer are clustered into Group II and show water quality that is only slightly affected by the contaminants originating from the land surface. However, groundwaters of this group are very high in Fe and Mn levels due to strong anoxic condition caused by the thick silt bed. In contrast, Group I shows water quality largely influenced by agricultural activities (i.e., fertilization, liming) and occurs in the area adjacent to the river where the silt bed is not observed and the sand aquifer is covered with sandy soils. Group III mostly occurs in the upgradient of Group I where a thin, silty soil covers the sand aquifer. In overall, the results show that the clustered groups closely reflect the groundwater susceptibility to the contaminants originated from the land surface. This suggests that groundwater clustering based on water chemistry could be applied to the contamination susceptibility assessment for groundwaters in the agricultural area.

Agriculture↗

PubMed2003

Isolation and characterization of bacteria capable of degrading phenol and reducing nitrate under low-oxygen conditions.

Nitrate-reducing bacteria capable of degrading phenol were isolated from natural and contaminated environments under low-oxygen conditions with nitrate-containing media, using phenol as a sole carbon and energy source. A total of 27 bacteria able to degrade phenol and reduce nitrate under low-oxygen conditions were isolated from all of the inoculum samples, regardless of previous phenol contamination. For all of these bacteria, oxygen was an essential requirement for phenol degradation. Nitrate reduction by 19 of the strains was insensitive to 10 mM sodium azide, and these strains were placed into the alpha- and beta-subclasses of Proteobacteria and two were Gram-positive bacteria. To date, the order of Rhizobiales has hardly been reported to have an ability to degrade aromatic compounds. Interestingly, our study showed that all isolates that were placed into the alpha-subclass of Proteobacteria are in the order of Rhizobiales. Furthermore, the genus Agrobacterium was isolated from most inoculum samples and one genus of Gram-positive bacteria, Staphylococcus, was also isolated. In the case of the remaining eight strains, nitrate reduction was inhibited by 10 mM sodium azide. Of these strains, seven were placed into the gamma-subclass of Proteobacteria.

Alphaproteobacteria↗

PubMed2003

Enhancement of sulfate reduction activity using granular sludge in anaerobic treatment of acid mine drainage.

Three laboratory-scale, upflow anaerobic reactors were operated for about 250 d to determine the effect of activated granular sludge with high density of sulfate reducing bacteria in the treatment of artificial acid mine drainage. Sulfate reducing bacteria in the granular sludge taken from the upflow anaerobic sludge blanket reactor were 1-2 x 10(6) c.f.u. g(-1), which is at least 10 times higher than that of organic substrates such as cow manure and oak compost. The reactors with granular sludge effectively removed over 99% of heavy metals, such as Fe, Al, Cu, and Cd during the experiment. This result suggests a feasibility of the application of granular sludge as a source of sulfate reducing bacteria for the treatment of acid mine drainage.

Anaerobiosis↗