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Biomedical subjects

Jang-Cheon Cho

Publications and source records attributed to Jang-Cheon Cho.

12 recordsLinked to original sources

Microbial metagenomes from Lake Soyang, the largest freshwater reservoir in South Korea.

Lake ecosystems play a fundamental role in the global biogeochemical cycling of essential elements such as carbon, nitrogen, and phosphorus. Microorganisms within these ecosystems mediate key processes that regulate these cycles. Metagenomic analyses provide valuable insights into the taxonomic and functional diversity of microbial communities in various environments, including freshwater habitats. Here, we present a comprehensive metagenomic dataset derived from Lake Soyang, the largest freshwater reservoir in South Korea. A total of 28 metagenomes were generated from water samples collected across two distinct sampling periods: the first set (n = 8) was obtained between April 2014 and January 2015 from two depths (1 m and 50 m) in four different seasons, while the second set (n = 20) was collected between January 2019 and November 2019 from five depths (1, 10, 20, 40, and 90 m) over four seasons. Metagenomic sequencing yielded 9.3-21.8 Gbp per sample. This dataset provides a valuable resource for future studies exploring the ecophysiological characteristics of microbial communities in pelagic freshwater environments.

Republic of Korea↗

Pelagibaca bermudensis gen. nov., sp. nov., a novel marine bacterium within the Roseobacter clade in the order Rhodobacterales.

A Gram-negative, chemoheterotrophic, facultatively anaerobic, slightly halophilic, oval-shaped marine bacterium, designated HTCC2601T, was isolated from the western Sargasso Sea by high-throughput culturing involving dilution to extinction. Although the 16S rRNA gene sequence similarity between the isolate and Salipiger mucosus was 96.5 %, phylogenetic analyses using different treeing algorithms clearly indicated that the strain forms a distinct lineage within a clade containing the recently classified genera Salipiger and Palleronia in the order Rhodobacterales of the Alphaproteobacteria. The DNA-DNA relatedness between strain HTCC2601T and S. mucosus was 26.3 %. Strain HTCC2601T utilized a wide range of carbohydrates, including hexose monomers, sugar alcohols, organic acids and amino acids, as sole carbon sources. The DNA G+C content of strain HTCC2601T was 65.4 mol%, and the predominant constituents of the cellular fatty acids were 18 : 1omega7c (79.7 %) and 11-methyl 18 : 1omega7c (7.5 %). The strain differed from members of the closely related genera Salipiger and Palleronia in its morphological, biochemical and ecological characteristics. On the basis of the taxonomic data obtained in this study, a novel genus and species, Pelagibaca bermudensis gen. nov., sp. nov., is proposed; HTCC2601T (=KCTC 12554T = JCM 13377T) is the type strain of Pelagibaca bermudensis.

Molecular Sequence Data↗

Proteorhodopsin in the ubiquitous marine bacterium SAR11.

Proteorhodopsins are light-dependent proton pumps that are predicted to have an important role in the ecology of the oceans by supplying energy for microbial metabolism. Proteorhodopsin genes were first discovered through the cloning and sequencing of large genomic DNA fragments from seawater. They were later shown to be widely distributed, phylogenetically diverse, and active in the oceans. Proteorhodopsin genes have not been found in cultured bacteria, and on the basis of environmental sequence data, it has not yet been possible to reconstruct the genomes of uncultured bacterial strains that have proteorhodopsin genes. Although the metabolic effect of proteorhodopsins is uncertain, they are thought to function in cells for which the primary mode of metabolism is the heterotrophic assimilation of dissolved organic carbon. Here we report that SAR11 strain HTCC1062 ('Pelagibacter ubique'), the first cultivated member of the extraordinarily abundant SAR11 clade, expresses a proteorhodopsin gene when cultured in autoclaved seawater and in its natural environment, the ocean. The Pelagibacter proteorhodopsin functions as a light-dependent proton pump. The gene is expressed by cells grown in either diurnal light or in darkness, and there is no difference between the growth rates or cell yields of cultures grown in light or darkness.

Alphaproteobacteria↗

A novel continuous toxicity test system using a luminously modified freshwater bacterium.

An automated continuous toxicity test system was developed using a recombinant bioluminescent freshwater bacterium. The groundwater-borne bacterium, Janthinobacterium lividum YH9-RC, was modified with luxAB and optimized for toxicity tests using different kinds of organic carbon compounds and heavy metals. luxAB-marked YH9-RC cells were much more sensitive (average 7.3-8.6 times) to chemicals used for toxicity detection than marine Vibrio fischeri cells used in the Microtox assay. Toxicity tests for wastewater samples using the YH9-RC-based toxicity assay showed that EC50-5 min values in an untreated raw wastewater sample (23.9 +/- 12.8%) were the lowest, while those in an effluent sample (76.7 +/- 14.9%) were the highest. Lyophilization conditions were optimized in 384-multiwell plates containing bioluminescent bacteria that were pre-incubated for 15 min in 0.16 M of trehalose prior to freeze-drying, increasing the recovery of bioluminescence and viability by 50%. Luminously modified cells exposed to continuous phenol or wastewater stream showed a rapid decrease in bioluminescence, which fell below detectable range within 1 min. An advanced toxicity test system, featuring automated real-time toxicity monitoring and alerting functions, was designed and finely tuned. This novel continuous toxicity test system can be used for real-time biomonitoring of water toxicity, and can potentially be used as a biological early warning system.

Biological Assay↗

Oceanicola granulosus gen. nov., sp. nov. and Oceanicola batsensis sp. nov., poly-beta-hydroxybutyrate-producing marine bacteria in the order 'Rhodobacterales'.

Three Gram-negative, chemoheterotrophic, non-motile, rod-shaped bacterial strains that accumulate poly-beta-hydroxybutyrate granules were isolated from the Bermuda Atlantic Time-series Study site by high-throughput culturing methods and characterized by polyphasic approaches. DNA-DNA hybridization, DNA G+C content and phylogenetic analyses based on 16S rRNA gene sequences divided the three isolates into two distinct genospecies that were clearly differentiated by fatty acid profiles, carbon source utilization patterns, antibiotic susceptibility and biochemical characteristics. The strains utilized a wide range of substrates, including pentoses, hexoses, oligosaccharides, sugar alcohols, organic acids and amino acids. DNA G+C contents were 71.5, 70.9 and 67.3 mol% for strains HTCC2516T, HTCC2523 and HTCC2597T, respectively. The most dominant fatty acid was 18 : 1omega7c in strains HTCC2516T and HTCC2523, and cyclo 19 : 0 in strain HTCC2597T. The type strains HTCC2516T and HTCC2597T were clearly differentiated by the presence or absence of 12 : 0, 12 : 1omega11c, 14 : 0, 15 : 0 and methyl 18 : 1. Phylogenetic analyses indicated that the strains formed a distinct monophyletic lineage within the Roseobacter clade in the order 'Rhodobacterales' of the Alphaproteobacteria, and which did not associate with any of the described genera. Genotypic and phenotypic differences of the isolates from the previously described genera support the description of Oceanicola granulosus gen. nov., sp. nov. with the type strain HTCC2516T (=ATCC BAA-861T=DSM 15982T=KCTC 12143T) and of Oceanicola batsensis sp. nov. with the type strain HTCC2597T (=ATCC BAA-863T=DSM 15984T=KCTC 12145T).

Acids↗

Robiginitalea biformata gen. nov., sp. nov., a novel marine bacterium in the family Flavobacteriaceae with a higher G+C content.

Two Gram-negative, chemoheterotrophic, non-motile, rust-coloured, marine strains were isolated from the western Sargasso Sea by high-throughput culturing. Characterization of the two strains by polyphasic approaches indicated that they are members of the same species. Phylogenetic analyses based on 16S rRNA gene sequences using three treeing algorithms revealed that the strains formed a coherent and novel genus-level lineage within the family Flavobacteriaceae. The dominant fatty acids were branched or hydroxy acids, i15 : 0, i15 : 1 and 3-OH i17 : 0 being the most abundant. The higher DNA G+C content of the strains (55-56 mol%) clearly differentiated them from other genera of the family Flavobacteriaceae (27-44 mol%). It is proposed, from the polyphasic evidence, that the strains be placed into a novel genus and a novel species named Robiginitalea biformata gen. nov., sp. nov., with strain HTCC2501T (=ATCC BAA-864T=KCTC 12146T) as the type strain.

Atlantic Ocean↗

Lentisphaera araneosa gen. nov., sp. nov, a transparent exopolymer producing marine bacterium, and the description of a novel bacterial phylum, Lentisphaerae.

Two phylogenetically distinct marine strains producing transparent exopolymers (TEP), designated HTCC2155(T) and HTCC2160, were cultivated from Oregon coast seawater by dilution to extinction in a high throughput culturing format. When cultured in low-nutrient seawater media, these strains copiously produced Alcian Blue-stainable viscous TEP. Growing cells were attached to each other by the TEP in a three dimensional network. Polymerase chain reaction employing 16S rDNA primers specific for the novel isolates indicated that they are indigenous to the water column of the Atlantic and Pacific oceans. The abundance of the isolates as determined by 16S rRNA dot blots, however, indicated that they are less than 1% of the total bacterial community. In phylogenetic analyses, the strains consistently formed a new phylum-level lineage within the domain Bacteria, together with members of the candidate phylum VadinBE97, which consists of Victivallis, the first cultured genus in the candidate phylum, and 16S rRNA gene clones from DNA extracted from marine or anaerobic terrestrial habitats. Five putative subgroups were delineated within this phylum-level lineage, including a marine group and an anaerobic group. The isolates are Gram negative, strictly aerobic, chemoheterotrophic, and facultatively oligotrophic sphere-shaped bacteria. The DNA G+C content of strain HTCC2155(T) was 48.3 mol% and the genome size was 2.9 mb. It is proposed from these observations that the strains be placed into a new genus and a new species named Lentisphaera araneosa (type strain HTCC2155(T) = ATCC BAA-859(T) = KCTC 12141(T)) gen. nov., sp. nov., the cultured marine representative of the Lentisphaerae phyl. nov., and the phylum be divided into two novel orders named the Lentisphaerales ord. nov. and the Victivallales ord. nov.

Bacteria↗

Cultivation and growth characteristics of a diverse group of oligotrophic marine Gammaproteobacteria.

Forty-four novel strains of Gammaproteobacteria were cultivated from coastal and pelagic regions of the Pacific Ocean using high-throughput culturing methods that rely on dilution to extinction in very low nutrient media. Phylogenetic analysis showed that the isolates fell into five rRNA clades, all of which contained rRNA gene sequences reported previously from seawater environmental gene clone libraries (SAR92, OM60, OM182, BD1-7, and KI89A). Bootstrap analyses of phylogenetic reliability did not support collapsing these five clades into a single clade, and they were therefore named the oligotrophic marine Gammaproteobacteria (OMG) group. Twelve cultures chosen to represent the five clades were successively purified in liquid culture, and their growth characteristics were determined at different temperatures and dissolved organic carbon concentrations. The isolates in the OMG group were physiologically diverse heterotrophs, and their physiological properties generally followed their phylogenetic relationships. None of the isolates in the OMG group formed colonies on low- or high-nutrient agar upon their first isolation from seawater, while 7 of 12 isolates that were propagated for laboratory testing eventually produced colonies on 1/10 R2A agar. The isolates grew relatively slowly in natural seawater media (1.23 to 2.63 day(-1)), and none of them grew in high-nutrient media (>351 mg of C liter(-1)). The isolates were psychro- to mesophilic and obligately oligotrophic; many of them were of ultramicrobial size (<0.1 micro m(3)). This cultivation study revealed that sporadically detected Gammaproteobacteria gene clones from seawater are part of a phylogenetically diverse constellation of organisms mainly composed of oligotrophic and ultramicrobial lineages that are culturable under specific cultivation conditions.

Bacteriological Techniques↗

Proteomic analysis of novel marine bacteria using MALDI and ESI mass spectrometry.

The objective of this study was to develop a mass spectrometric protocol to search for proteins related to phototrophy in marine bacteria. The genes that produce proteins involved in conversion of light into energy have been detected by cloning-sequencing from some of these bacteria, but it was previously unknown if these proteins were actually expressed. Attaining this study's goal was complicated by the fact that the samples consisted of miniscule cell pellets, which yielded small amounts of very complex mixtures of proteins. Sample preparation and analysis were tailored to optimize the probability of detecting the proteins of interest. It has been reported that using both matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) to analyze a mixture of peptides leads to the identification of more peptides that either technique alone. In order to exploit this complementarity between ESI and MALDI for proteomic analysis, samples were analyzed using both ionization techniques. With correct choices in sample preparation and ionization process, biologically relevant proteins can be identified out of small samples containing whole proteomes.

Alphaproteobacteria↗

Croceibacter atlanticus gen. nov., sp. nov., a novel marine bacterium in the family Flavobacteriaceae.

A bright, saffron-colored marine bacterium HTCC2559T was isolated from the Bermuda Atlantic Time Series station in the western Sargasso Sea, Atlantic Ocean by high throughput culturing methods and characterized by polyphasic approaches. Phenotypic data and phylogenetic analyses showed that the strain is a member of the family Flavobacteriaceae. The strain was gram-negative, non-motile, chemoheterotrophic, strictly aerobic, NaCl-requiring, rod-shaped cells that contain carotenoid pigments but not flexirubin. Several kinds of macromolecules (gelatin, DNA, starch, casein, and elastin) were degraded and carbohydrates, sugar alcohols, organic acids, and amino acids were utilized as sole carbon sources. The dominant fatty acids were branched or hydroxy acids, and 3-OH i17:0, i15:0, i15:1, and i17:1 omega9c were abundant. The DNA G+C content of the strain is 34.8 mol%. Phylogenetic analyses using three treeing algorithms based on 16S rRNA gene sequences revealed that the strain formed a very distinct lineage that is allied closely with several seawater environmental clones in the family Flavobacteriaceae. Therefore, it is proposed from the polyphasic studies that strain HTCC2559T (=ATCC BAA-628T = KCTC 12090T) belongs to a new genus and species named Croceibacter atlanticus gen. nov., sp. nov.

Biodegradation, Environmental↗

Parvularcula bermudensis gen. nov., sp. nov., a marine bacterium that forms a deep branch in the alpha-Proteobacteria.

Two bacterial strains, HTCC2503T and HTCC2517, were isolated from the Bermuda Atlantic Time Series Station in the western Sargasso Sea, Atlantic Ocean, by new high-throughput culture methods that rely on dilution to extinction in very-low-nutrient media. Characterization of the two strains by polyphasic approaches revealed that they belonged to the same species. These isolates are gram-negative, strictly aerobic, chemoheterotrophic, slightly motile short rods with a single flagellum. The temperature, pH and NaCl concentration ranges for growth were 10-37 degrees C, 6.0-9.0 and 0.75-20% (w/v), respectively. Colonies on marine agar were very small (0.3-0.8 mm in diameter), yellowish-brown and very hard. Carotenoid pigments were synthesized but bacteriochlorophyll a was not. Several kinds of pentose, hexose, sugar alcohol, oligosaccharide and amino acid were utilized as sole carbon sources. Oxidase was produced, but catalase was not. All cellular fatty acids were even-numbered monounsaturated or saturated fatty acids and the major fatty acid was cis-7-octadecenoic acid (73.3%). The DNA G + C content of strain HTCC2503T was 60.8 mol%. Phylogenetic analyses of 16S rRNA gene sequences clearly indicated that the strains formed a distinct lineage, allied with activated sludge environmental clone H9, in the alpha-Proteobacteria. The clade containing strains HTCC2503T and HTCC2517 and clone H9 could not be phylogenetically associated with any of the six known orders of the alpha-Proteobacteria. From this polyphasic evidence, it is proposed that the novel strains should be classified as Parvularcula bermudensis gen. nov., sp. nov. The type strain is HTCC2503T (= ATCC BAA-594T = KCTC 12087T) and the reference strain is HTCC2517.

Alphaproteobacteria↗

Fulvimarina pelagi gen. nov., sp. nov., a marine bacterium that forms a deep evolutionary lineage of descent in the order "Rhizobiales".

Three brownish-yellow bacterial strains were isolated from the western Sargasso Sea by high-throughput culturing methods and characterized by polyphasic approaches. All isolates were Gram-negative, strictly aerobic, chemoheterotrophic, non-motile short rods that contained carotenoid pigments. Phylogenetic analyses based on 16S rRNA gene sequences, DNA-DNA hybridization and DNA G+C content, along with phenotypic characteristics, revealed that they belonged to the same species. The strains utilized a wide range of substrates, including pentoses, hexoses, oligosaccharides, sugar alcohols, organic acids and amino acids, as sole carbon sources. The DNA G+C content of the isolates ranged from 57.6 to 59.9 mol%. The predominant cellular fatty acid constituent was C(18 : 1)omega7c, whilst C(16 : 0), C(18 : 0) and C(19 : 0)omega8c cyclo were also abundant. The organism related most closely to these strains, as determined by 16S rDNA sequence comparison, was the recently described species Aurantimonas coralicida (93.3-93.8 % similarity). Phylogenetic analyses indicated that the strains formed a distinct and deep evolutionary lineage of descent, together with A. coralicida, within the order "Rhizobiales" of the alpha-Proteobacteria. This lineage could not be associated with any of the ten known families in the order "Rhizobiales". From polyphasic evidence, it is proposed that the strains be placed into a novel genus and species, Fulvimarina pelagi gen. nov., sp. nov. (type strain, HTCC2506(T)=ATCC BAA-666(T)=KCTC 12091(T)=DSM 15513(T)).

Microbial Sensitivity Tests↗