Geon-Hyoung Lee

Strombidinopsis jeokjo n. sp. (ciliophora: choreotrichida) from the coastal waters off western Korea: morphology and small subunit ribosomal DNA gene sequence.

Abstract The planktonic ciliate Strombidinopsis jeokjo n. sp. is described from Quantitative Protargol-Stained (QPS) preparations, and the sequence of the small subunit rDNA (SSU rDNA) from cultured cells is reported. This species is ovoid and bluntly tapered towards the posterior. The ranges (and mean ± standard deviation, n = 31) of cell length, cell width, and oral diameter of the QPS-stained specimens were 100–190 μm (149 ± 25), 60–105 μm (79 ± 13), and 55–80 μm (64 ± 5), respectively. Fifteen to seventeen external oral polykinetids had oral membranelle cilia 20–35 μm long. Twenty-six to twenty-eight somatic kineties were equally spaced around the cell body and extended from the oral to the posterior regions with 23–44 dikinetids per kinety. Both kinetosomes of each kinetid bore cilia 3–7 μm long. Strombidinopsis jeokjo had two ovoid macronuclei of 25–38 μm × 12–15 μm. When properly aligned, the sequence of the SSU rDNA of S. jeokjo (GenBank Accession No. AJ628250) was approximately 2% different from that of an unidentified Strombidinopsis species (GenBank Accession No. AF399132-AF399135), the closest species in the SSU rDNA sequence.

Alkaline stress‐induced autophagy is mediated by mTORC1 inactivation

The activation of autophagic pathway by alkaline stress was investigated. Various types of mammalian cells were subjected to alkaline stress by incubation in bicarbonate buffered media in humidified air containing atmospheric 0.04% CO2. The induction of autophagy following alkaline stress was evaluated by assessing the conversion of cytosolic LC3‐I into lipidated LC3‐II, the accumulation of autophagosomes, and the formation of autolysosomes. Colocalization of GFP‐LC3 with endolysosomal marker in HeLa GFP‐LC3 cells undergoing autophagic process by alkaline stress further demonstrates that autophagosomes triggered by alkaline stress matures into autolysosomes for the lysosome dependent degradation. We found that the inactivation of mTORC1 is important for the pathway leading to the induction of autophagy by alkaline stress since the expression of RhebQ64L, a constitutive activator of mTORC1, downregulates the induction of autophagy after alkaline stress in transfected human 293T cells. These results imply that activation of autophagic pathway following the inactivation of mTORC1 is important cellular events governing alkaline stress‐induced cytotoxicity and clinical symptoms associated with alkalosis. J. Cell. Biochem. 112: 2566–2573, 2011.

Annual Population Variation and Identification of Antibiotic-Resistant Bacteria in the Lower Lake Geumgang

This study was conducted to evaluate the annual population variation and identification of antibiotic-resistant bacteria in the lower artificial Lake Geumgang from January to December, 2002. Samples were taken from the surface waters at 3 stations near the estuarine barrage. The results were as follows; the population densities of heterotrophic bacteria varied from 4.1±1.0×10² to 6.7±1.1×10³ cfu ml/sup -1/ during the investigation periods. The population densities of antibiotic-resistant bacteria ranged from 1.5±0.7×10 to 4.3±0.3×10³ cfu ml/sup -1/ for ampicillin; from 0 to 6.4±0.4× 10² cfu ml/sup -1/ for chloramphenicol; from 0 to 2.8±0.3×10³ cfu ml/sup -1/ for gentamicin; from 0 to 4.5±1.0×10³ cfu ml/sup -1/ for kanamycin; and from 1.0±0.4 × 10 to 2.3±0.5×10³ cfu ml/sup -1/ for streptomycin, respectively. Of the sixty isolates, 90% were Gram negative. Dominant genera by 16S rDNA analysis were identified Aeromonas spp. (14 strains), Bacillus spp. (6 strains), Enterobacter spp. (4 strains), and Stenotrophomonas spp. (6 strains). These strains were clustered into 12 groups based on relatedness by average linkage method. Of the 60 isolates, 85% had the resistance to ampicilin and 32% were shown resistance to more than 2 kinds of antibiotics.

Paenibacillus insulae sp. nov., isolated from soil.

A Gram-stain-positive, motile, endospore-forming, and strictly aerobic rod-shaped bacterium designated DS80T was isolated from an island soil. The strain DS80T grew at temperatures between 15 and 40°C (optimum = 30°C) and at pH values ranging from 5.0 to 9.0 (optimum = 7.0). The phylogenetic analysis based on the comparisons of the 16S rRNA gene sequences showed that the isolate was affiliated to the genus Paenibacillus and was mostly related to Paenibacillus assamensis GPTSA11T (with the sequence similarity of 96.33%) and Paenibacillus urinalis 5402403T(95.48%). The G+C content of the genomic DNA was 44.0 mol% and the major fatty acids were anteiso-C15:0, iso-C15:0, iso-C16:0, and C16:1ω11c. Strain DS80T contained MK-7 as the major menaquinone, and phosphatidylglycerol, phosphatidylethanolamine, and diphosphatidylglycerol as the major polar lipids. The peptidoglycan contained a major amount of meso-diaminopimelic acid. The chemotaxonomic profile of strain DS80T was consistent with that of Paenibacillus. However, the phenotypic properties clearly separated the strain from other species of the genus. Accordingly, a new species, Paenibacillus insulae sp. nov., is proposed (type strain =DS80T =JCM 17278T =KCTC 13833T).

Bacterial Diversity in the Rhizosphere of Halophyte Suaeda japonica in Western and Southern Mudflats of Korea

This study was carried out to investigate the population densities, R/S ratios, and identification of heterotrophic bacteria on the rhizosphere soil of halophyte Suaeda japonica found on the western and southern mudflats of Korea. The population densities of aerobic and anaerobic heterotrophic bacteria on the rhizosphere soil of Suaeda japonica were in the range of , respectively. In case of physiologically specific bacteria, population densities of amylolytic bacteria on the rhizosphere soil of Suaeda japonica were in the range of , those of cellulolytic bacteria were from , and those of proteolytic bacteria were from , respectively. The R/S ratios were ranged from 2.33 to 2.39. Among eleven isolates from the roots of halophyte Suaeda japonica of Goheung bay by using 16S rDNA analysis, five clones were closely related to group and six clones were closely related to group. Among four isolates from Suncheon bay, two strains were related to group and another two were related to Actinobacteria and Bacilli group, respectively.

Characteristics of Heterotrophic Bacterial Population in the Artificial Lake Geumgang Near Estuary Barrage

The monthly variations of physico-chemical and microbiological water quality were investigate in the artificial Lake Geumgang near estuary barrage. Sixty heterotrophic bacteria were isolated and identified by amplification and sequencing of 16S rDNA. Water temperature, pH, and inorganic nutrients(-N, -N, -N, -P) were measured. Concentrations of DO, BOD, and inorganic nutrients were lower than in the middle-stream of Geum river The population densities of heterotrophic bacteria and total coliforms varied from to , and 0 to , respectively. Among the measured numbers of physiological groups of bacteria, cellulolytic bacteria showed higher population densities than those of other physiological groups. Bacterial community structure was analysed based on 16S rDNA partial sequencing. Among 60 isolates, dominant genus was Pseudomones (20 strains).