Biomedical subjects

Jongsik Chun

Publications and source records attributed to Jongsik Chun.

At least 19 recordsLinked to original sources

PubMed2007

Demequina aestuarii gen. nov., sp. nov., a novel actinomycete of the suborder Micrococcineae, and reclassification of Cellulomonas fermentans Bagnara et al. 1985 as Actinotalea fermentans gen. nov., comb. nov.

An actinobacterial strain containing demethylmenaquinone DMK-9(H(4)) as the diagnostic isoprenoid quinone was isolated from a tidal flat sediment sample, from South Korea. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain JC2054(T) represents a distinct phyletic line within the suborder Micrococcineae of the order Actinomycetales. The closest phylogenetic neighbour was Cellulomonas fermentans, with 94.7 % 16S rRNA gene sequence similarity. The novel isolate was strictly aerobic and slightly halophilic, with optimum growth occurring in 2-4 % (w/v) NaCl. Cells were non-motile, non-sporulating and rod-shaped. The peptidoglycan type was of the A-type of cross-linkage. l-ornithine was the diamino acid and d-glutamate represented the N-terminus of the interpeptide bridge. The predominant fatty acids were anteiso-branched and straight-chain fatty acids. The major polar lipids were phosphatidylinositol, diphosphatidylglycerol and an unknown phospholipid. The menaquinone composition of C. fermentans was determined to be MK-10(H(4)), MK-9(H(4)) and MK-8(H(4)) in the ratio 56 : 2 : 1. On the basis of the polyphasic evidence presented in this study, it is proposed that strain JC2054(T) should be classified as representing a novel genus and species of the suborder Micrococcineae, with the name Demequina aestuarii gen. nov., sp. nov. The type strain is JC2054(T) (=IMSNU 14027(T)=KCTC 9919(T)=JCM 12123(T)). In addition, it was clear from the phylogenetic analysis and chemotaxonomic data that C. fermentans does not belong to the genus Cellulomonas or any other recognized genera. Therefore, C. fermentans should be reclassified as representing a novel genus, for which the name Actinotalea fermentans gen. nov., comb. nov. is proposed, with strain DSM 3133(T) (=ATCC 43279(T)=CFBP 4259(T)=CIP 103003(T)=NBRC 15517(T)=JCM 9966(T)=LMG 16154(T)) as the type strain.

Actinomycetales↗

PubMed2006

Comparative analysis of growth-phase-dependent gene expression in virulent and avirulent Streptococcus pneumoniae using a high-density DNA microarray.

The global pattern of growth-dependent gene expres-sion in Streptococcus pneumoniae strains was evalu-ated using a high-density DNA microarray. Total RNAs obtained from an avirulent S. pneumoniae strain R6 and a virulent strain AMC96-6 were used to compare the expression patterns at seven time points (2.5, 3.5, 4.5, 5.5, 6.0, 6.5, and 8.0 h). The expression profile of strain R6 changed between log and station-ary growth (the Log-Stat switch). There were clear differences between the growth-dependent gene ex-pression profiles of the virulent and avirulent pneumo-coccal strains in 367 of 1,112 genes. Transcripts of genes associated with bacterial competence and capsular polysaccharide formation, as well as clpP and cbpA, were higher in the virulent strain. Our data suggest that late log or early stationary phase may be the most virulent phase of S. pneumoniae.

Gene Expression Profiling↗

PubMed2006

Clostridium ganghwense sp. nov., isolated from tidal flat sediment.

A Gram-negative, strictly anaerobic, halophilic, motile, sporulating and rod-shaped bacterium, designated strain HY-42-06T, was isolated from tidal flat sediment from Ganghwa Island in South Korea. The isolate produced glycerol, ethanol and CO2 as fermentation end-products from glucose. Strain HY-42-06T grew optimally at 35 degrees C, pH 7.5 and 3 % (w/v) artificial sea salts. No growth was observed in the absence of sea salts. In phylogenetic analyses based on 16S rRNA gene sequence, strain HY-42-06T showed a distinct phyletic line within the members of cluster I of the order Clostridiales. The closest phylogenetic neighbour to strain HY-42-06T was Clostridium novyi ATCC 17861T (94.91 % 16S rRNA gene sequence similarity). Several phenotypic characters readily differentiate the tidal flat isolate from phylogenetically related clostridia. On the basis of polyphasic evidence, strain HY-42-06T should be classified as a representative of a novel species, for which the name Clostridium ganghwense sp. nov. is proposed. The type strain is HY-42-06T (=IMSNU 40127T = KCTC 5146T = JCM 13193T).

Clostridium↗

PubMed2006

Pseudomonas segetis sp. nov., isolated from soil.

A Gram-negative, aerobic bacterium, designated strain FR1439T, was isolated from the soil of Dokdo in the Republic of Korea. The cells of strain FR1439T were catalase- and oxidase-positive, motile and rod-shaped. Phylogenetic analysis of the 16S rRNA gene sequence revealed that it represents a distinct line of descent within the genus Pseudomonas. The levels of DNA-DNA relatedness between strain FR1439T and type strains of phylogenetically related species, namely Pseudomonas flavescens, Pseudomonas mendocina, Pseudomonas pseudoalcaligenes and Pseudomonas straminea, ranged from 28 to 37%. Several phenotypic characteristics, together with the cellular fatty acid composition, can be used to differentiate strain FR1439T from related pseudomonads. On the basis of the polyphasic taxonomic evidence presented in this study, strain FR1439T represents a novel species, for which the name Pseudomonas segetis sp. nov. is proposed. The type strain is FR1439T (=IMSNU 14101T=CIP 108523T=KCTC 12331T).

Bacterial Typing Techniques↗

PubMed2006

Photobacterium ganghwense sp. nov., a halophilic bacterium isolated from sea water.

A marine bacterial strain, designated FR1311T, was isolated from a sea-water sample from Ganghwa Island, South Korea. Cells were Gram-negative, facultatively anaerobic, catalase- and oxidase-positive, motile, oval or rod-shaped and halophilic (optimum sea-salt concentration for growth of 5-6 %). Phylogenetic analysis of its 16S rRNA gene sequence revealed that it represented a distinct line of descent within the genus Photobacterium. The major fatty acids were straight-chain saturated (C(16 : 0)) and monounsaturated fatty acids (C(16 : 1)omega7c and C(18 : 1)omega7c). The predominant respiratory lipoquinone was Q-8. The DNA G+C content was 44 mol%. The phenotypic features of strain FR1199T were similar to those of Photobacterium damselae subsp. damselae and Photobacterium damselae subsp. piscicida, but several physiological and chemotaxonomic properties readily distinguish the new isolate from them. On the basis of the polyphasic results revealed in this study, FR1311T is considered to be the type strain of a novel species, for which the name Photobacterium ganghwense sp. nov. is proposed. The type strain is FR1311T (=IMSNU 60287T = KCTC 12328T = JCM 12487T).

DNA, Bacterial↗

PubMed2006

Jannaschia seosinensis sp. nov., isolated from hypersaline water of a solar saltern in Korea.

A slightly halophilic alphaproteobacterium, designated CL-SP26T, was isolated from hypersaline water of a solar saltern located in Seosin, Korea. 16S rRNA gene sequence analysis revealed an affiliation with the genus Jannaschia. Sequence similarities between CL-SP26T and type strains of members of the genus Jannaschia were 94.9-97.2 %. Cells were rod-shaped and motile with one or more monopolar flagella. Strain CL-SP26T grew on solid media as circular red colonies. It was able to grow in 3-10 % sea salt; however, no growth occurred in media containing NaCl as the only salt. Strain CL-SP26T grew at 5-35 degrees C and pH 7-10. The major fatty acids were 18 : 1omega7c (64 %) and 18 : 0 (12.0 %). Three fatty acids, 3-OH 14 : 0/iso 16 : 1 (3.6 %), 18 : 3omega6c (2.2 %) and 10-methyl 19 : 0 (1.9 %), found in minor quantities in CL-SP26(T), are unique among Jannaschia species. The DNA G+C content was 63 mol%. According to physiological data, fatty acid composition and 16S rRNA gene sequence analysis, CL-SP26T was assigned to the genus Jannaschia, but could be distinguished from recognized species of the genus. Strain CL-SP26T (= KCCM 42114T = JCM 13035T) therefore represents a novel species, for which the name Jannaschia seosinensis sp. nov. is proposed.

Alphaproteobacteria↗

PubMed2006

Tenacibaculum litoreum sp. nov., isolated from tidal flat sediment.

A rod-shaped bacterium, designated CL-TF13T, was isolated from a tidal flat in Ganghwa, Korea. Analysis of the 16S rRNA gene sequence revealed an affiliation with the genus Tenacibaculum. The sequence similarities between CL-TF13T and type strains of members of the genus Tenacibaculum were from 94.2 to 97.4%. Cells were motile by means of gliding. Strain CL-TF13T grew on solid medium as pale-yellow colonies with an irregular spreading edge. The strain was able to grow in NaCl at a range of 3-5%. They grew within a temperature range of 5-40 degrees C and at pH range of 6-10. The major fatty acids were summed feature 3 (C(16:1)omega7c and/or iso-C(15:0) 2-OH, 19.6%), iso-C(15:0) (18.8%) and iso-C(17:0) 3-OH (13.6%). Fatty acids such as C(18:3)omega6c (6,9,12) (1.5%) and summed feature 4 (iso I- and/or anteiso B-C(17:1), 1.3%) were uniquely found in minor quantities in CL-TF13T among Tenacibaculum species. The DNA G + C content was 30 mol%. According to physiological data, fatty-acid composition and 16S rRNA gene sequence, CL-TF13T could be assigned to the genus Tenacibaculum but distinguished from the recognized species of the genus. Therefore, strain CL-TF13T (= KCCM 42115T = JCM 13039T) represents a novel species, for which the name Tenacibaculum litoreum sp. nov. is proposed.

DNA, Ribosomal↗

PubMed2006

Flavobacterium weaverense sp. nov. and Flavobacterium segetis sp. nov., novel psychrophiles isolated from the Antarctic.

Two psychrophilic flavobacteria, designated AT1042(T) and AT1048(T), were isolated from terrestrial samples from the Antarctic. Results of 16S rRNA gene sequence analyses indicated a close relationship of these isolates to Flavobacterium flevense (96.9 % similarity for strain AT1042(T)) and Flavobacterium psychrolimnae (97.0 % for strain AT1048(T)). Cells were non-motile and non-gliding. Flexirubin-type pigments were absent. Both isolates were psychrophilic, with an optimum and maximum growth temperature of about 15 and 20 degrees C, respectively. The major isoprenoid quinone, predominant cellular fatty acids and DNA G+C contents (35-37 mol%) were consistent with the placement of the Antarctic isolates in the genus Flavobacterium. Phylogeny based on 16S rRNA gene sequences and several phenotypic characteristics could be used to differentiate these isolates from recognized Flavobacterium species. Despite high 16S rRNA gene sequence similarity (98.9 %) between strains AT1042(T) and AT1048(T), they represented two distinct species as demonstrated by low genomic relatedness (34 %) and a number of differential phenotypic characters. The polyphasic data presented in this study indicated that the new isolates should be classified within two novel species in the genus Flavobacterium. The names Flavobacterium weaverense sp. nov. (type strain AT1042(T) = IMSNU 14048(T) = KCTC 12223(T) = JCM 12384(T)) and Flavobacterium segetis sp. nov. (type strain AT1048(T) = IMSNU 14050(T) = KCTC 12224(T) = JCM 12385(T)) are proposed for these Antarctic isolates.

Antarctic Regions↗

PubMed2006

Hymenobacter rigui sp. nov., isolated from wetland freshwater.

A non-motile, rod-shaped and pinkish-red-pigmented bacterium, designated strain WPCB131(T), was isolated from freshwater of Woopo wetland, Republic of Korea. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that this isolate represents a novel member of the genus Hymenobacter with sequence similarities of 93.2-95.5 % to known Hymenobacter species. No other taxa in the phylum Bacteroidetes showed more than 90 % sequence similarity to the isolate. Cells were Gram-negative, oxidase-negative and catalase-positive. Optimum growth was observed at pH 6 and 30 degrees C. The major fatty acids were iso-C(15 : 0) (34.8 %), C(16 : 1)omega5c (15.0 %), anteiso-C(17 : 1) B/iso-C(17 : 1) I (14.4 %) and C(16 : 1)omega7c/iso-C(15 : 0) 2-OH (13.8 %). The DNA G+C content of strain WPCB131(T) was 65 mol%. The isolate could be readily distinguished from other Hymenobacter species using a combination of phenotypic characters. On the basis of the polyphasic evidence presented in this study, it is proposed that strain WPCB131(T) (=IMSNU 14116(T)=KCTC 12533(T)=NBRC 101118(T)) represents a novel species, Hymenobacter rigui sp. nov.

Bacterial Typing Techniques↗

PubMed2006

Glaciecola nitratireducens sp. nov., isolated from seawater.

A marine bacterial strain, FR1064(T), was isolated from a surface seawater sample collected off Jeju Island, South Korea. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate belonged to the Gammaproteobacteria and was related to the genus Glaciecola with 97.6 % sequence similarity to Glaciecola pallidula, its nearest phylogenetic neighbour. DNA-DNA relatedness between strain FR1064(T) and G. pallidula ACAM 615(T) was 55 %. Cells of the novel isolate were Gram-negative, aerobic, rod-shaped, motile and halophilic, with an optimum sea salts concentration of 4-7 %. The major fatty acids were straight-chain saturated (C(16 : 0)), summed feature 3 and monounsaturated fatty acid C(18 : 1). The DNA G+C content was 44 mol%. Several phenotypic characteristics differentiated the novel isolate from all previously described members of the genus Glaciecola. The polyphasic data obtained in this study clearly demonstrate that strain FR1064(T) represents a novel species of the genus Glaciecola. The name Glaciecola nitratireducens sp. nov. is therefore proposed, with strain FR1064(T) (=KCTC 12276(T)=JCM 12485(T)) as the type strain.

Alteromonadaceae↗

PubMed2006

Multilocus sequence typing (MLST) analysis of Vibrio cholerae O1 El Tor isolates from Mozambique that harbour the classical CTX prophage.

Vibrio cholerae O1 isolates belonging to the Ogawa serotype, El Tor biotype, harbouring the classical CTX prophage were first isolated in Mozambique in 2004. Multilocus sequence typing (MLST) analysis using nine genetic loci showed that the Mozambique isolates have the same sequence type (ST) as O1 El Tor N16961, a representative of the current seventh cholera pandemic. Analysis of the CTX prophage in the Mozambique isolates indicated that there is one type of rstR in these isolates: the classical CTX prophage. It was also found that the ctxB-rstR-rstA-rstB-phs-cep fragment was PCR-amplified from these isolates, which indicates the presence of a tandem repeat of the classical CTX prophage in the genome of the Mozambique isolates. The possible origin of these isolates and the presence of the tandem repeat of the classical prophage in them implicate the presence of the classical CTX phage.

Bacterial Proteins↗

PubMed2006

Isolation of Salmonella enterica subspecies enterica serovar Paratyphi B dT+, or Salmonella Java, from Indonesia and alteration of the d-tartrate fermentation phenotype by disrupting the ORF STM 3356.

Salmonella enterica subspecies enterica serovar Paratyphi B [O1,4,(5),12 : Hb : 1,2] can cause either an enteric fever (paratyphoid fever) or self-limiting gastroenteritis in humans. The d-tartrate non-fermenting variant S. enterica subsp. enterica serovar Paratyphi B dT- (S. Paratyphi B) is the causative agent of paratyphoid fever, and the d-tartrate fermenting variant S. enterica subsp. enterica serovar Paratyphi B dT+ (S. Paratyphi B dT+; formerly called Salmonella Java) causes gastroenteritis. S. Java is currently recognized as an emerging problem worldwide. Twelve dT+ S. Java isolates were collected in Indonesia between 2000 and 2002. One-third of them contained Salmonella genomic island 1 (SGI1), which gives the multidrug-resistant phenotype to the bacteria. In this study, a PCR-based method to detect a single nucleotide difference responsible for the inability to ferment d-tartrate, reported elsewhere, was validated. The d-tartrate fermenting phenotype of S. Java was converted to the non-fermenting phenotype by the disruption of the ORF STM 3356, and the d-tartrate non-fermenting phenotype of the ORF STM 3356-disrupted strain and the dT- reference strain was changed to the dT+ phenotype by complementing ORF STM 3356 in trans. The results show that the dT+ phenotype requires a functional product encoded by STM 3356, and support the use of the PCR-based discrimination method for S. Paratyphi B and S. Java as the standard differentiation method.

Anti-Bacterial Agents↗

PubMed2006

Thalassobius aestuarii sp. nov., isolated from tidal flat sediment.

A strictly aerobic, non-motile, ovoid-shaped Alphaproteobacteria, designated strain JC2049(T), was isolated from a tidal flat sediment sample. The results of 16S rRNA gene sequence analysis indicated that this isolate belonged to the genus Thalassobius, with a sequence similarity of 96.9-97.3% to other valid Thalassobius spp. The cells required 1-7% NaCl for growth (optimum 2%) and accumulated poly-beta-hydroxybutyrate. Nitrite was reduced to nitrogen, but nitrate was not reduced to nitrite. No genetic potential for aerobic anoxygenic photosynthesis was detected. The primary isoprenoid quinone (Ubiquinone-10), predominant cellular fatty acids (C(18:1)omega7c, 11 methyl C(18:1)omega7c and C(16:0)) and DNA G+C content (61 mol%) were all consistent with the assignment of this isolate to the genus Thalassobius. Several phenotypic characteristics clearly distinguished our isolate from other Thalassobius species. The degree of genomic relatedness between strain JC2049(T) and other Thalassobius species was in a range of 20-43%. The polyphasic data presented in this study indicates that our isolate should be classified as a novel species within the genus Thalassobius. The name Thalassobius aestuarii sp. nov. is therefore proposed for this isolate; the type strain is JC2049(T) (= IMSNU 14011(T) = KCTC 12049(T) = DSM 15283(T)).

Fatty Acids↗

PubMed2005

Characterization of biofilm structure and its effect on membrane permeability in MBR for dye wastewater treatment.

Two membrane bioreactors were operated at aerobic (DO=6.0mg/L) and anoxic (DO<0.3mg/L) conditions for the treatment of synthetic dye wastewater to determine the effect of dissolved oxygen on membrane filterability. The rate of membrane fouling for the anoxic MBR was five times faster than that for the aerobic MBR. Differences in the nature of the biofilm that was formed on the membrane surface as the result of different DO level was the main factor in the different fouling rates. The biofilm structure was characterized using digital image analysis techniques. Biofilm images were obtained using confocal laser scanning microscopy (CLSM) at various operation points. Structural parameters were then computed from these images using an image analysis software (ISA-2). The structural parameters indicated that the anoxic biofilm was thinner than the aerobic biofilm but the anoxic biofilm was spread out on the membrane surface more uniformly and densely, resulting in the higher membrane fouling. Based on the extracellular polymeric substances (EPS) visualization and quantification, it was also found that EPS, key membrane foulants were spread out more uniformly in the anoxic biofilm in spite of lower amount of EPS compared to that in the aerobic biofilm.

Biofilms↗

PubMed2005

Bacterial community structure in kimchi, a Korean fermented vegetable food, as revealed by 16S rRNA gene analysis.

Kimchi is a traditional Korean food fermented from a variety of vegetables. We elucidated the microbial community structure of five commercially produced kimchis made from Chinese cabbage by examining culture-independent 16S rRNA gene clone libraries. Most of the clones (347 out of 348) belonged to lactic acid bacteria and included several species of the genera Lactobacillus, Leuconostoc and Weissella. Weissella koreensis was found in all the samples and predominated in three of them (42.6-82%). Leuconostoc gelidum, Leuconostoc gasicomitatum and Lactobacillus sakei were common in the remaining kimchi clone libraries (>34%). The composition of bacterial phylotypes in kimchi varied between samples. Our approach revealed different community structures from those reported in previous culture-dependent studies based on phenotypic identification methods. The culture-independent method used here proved to be efficient and accurate and showed that the bacterial communities in kimchi differ from those in other fermented vegetable foods.

Base Sequence↗

PubMed2005

Identification of essential genes in Streptococcus pneumoniae by allelic replacement mutagenesis.

To find potential targets of novel antimicrobial agents, we identified essential genes of Streptococcus pneumoniae using comparative genomics and allelic replacement mutagenesis. We compared the genome of S. pneumoniae R6 with those of Bacillus subtilis, Enterococcus faecalis, Escherichia coli, and Staphylococcus aureus, and selected 693 candidate target genes with > 40% amino acid sequence identity to the corresponding genes in at least two of the other species. The 693 genes were disrupted and 133 were found to be essential for growth. Of these, 32 encoded proteins of unknown function, and we were able to identify orthologues of 22 of these genes by genomic comparisons. The experimental method used in this study is easy to perform, rapid and efficient for identifying essential genes of bacterial pathogens.

Genes, Bacterial↗

PubMed2005

jPHYDIT: a JAVA-based integrated environment for molecular phylogeny of ribosomal RNA sequences.

jPHYDIT is a Java application designed to furnish a visual and integrated environment for molecular phylogeny. The program can be used to visualize intra-strand base-pairing information in secondary and tertiary structures of ribosomal RNA (rRNA) sequences. A function for the semi-automated alignment was included to facilitate handling of the database containing a large number of multiple-aligned rRNA sequences. Integration of nucleotide sequence editing, pairwise alignment, multiple alignment and phylogenetic treeing functions provide an easy and efficient way of analyzing rRNA sequences for molecular evolution, systematics, epidemiology and ecology.

Algorithms↗

PubMed2005

Sejongia antarctica gen. nov., sp. nov. and Sejongia jeonii sp. nov., isolated from the Antarctic.

Two yellow-pigmented, Gram-negative and aerobic bacterial strains, designated AT1013T and AT1047T, were isolated from terrestrial samples of the Antarctic. On the basis of 16S rRNA gene sequence analyses, the two Antarctic strains shared 97.7 % sequence similarity and showed moderate relationships to the genera Chryseobacterium (92.5-95.3 %), Riemerella (92.3-93.5 %), Bergeyella (92.5-92.6 %) and Kaistella (92.5-93.3 %). In phylogenetic analyses, the two isolates formed a robust monophyletic clade and represented a distinct phyletic line that equated to novel generic status. Cells were non-motile, non-gliding and psychrotolerant with an optimum growth temperature of about 20 degrees C. Flexirubins were absent. The major isoprenoid quinone was MK-6. The predominant cellular fatty acids were 15 : 0 iso, 15 : 0 anteiso and 17 : 1 iso omega9c. DNA G+C contents were 34-36 mol%. The two isolates shared low genomic relatedness (27 %) and were differentiated from each other by several phenotypic characteristics. The polyphasic data presented in this study indicated that these isolates should be recognized as two separate novel species in a novel genus within the family Flavobacteriaceae. The name Sejongia gen. nov. is therefore proposed for the Antarctic isolates, with the type species Sejongia antarctica sp. nov. (type strain AT1013T=IMSNU 14040T=KCTC 12225T=JCM 12381T) and Sejongia jeonii sp. nov. (type strain AT1047T=IMSNU 14049T=KCTC 12226T=JCM 12382T).

Antarctic Regions↗