Choong-Hwan Lee

Isolation and Characterization of a Novel Lipase from a Metagenomic Library of Tidal Flat Sediments: Evidence for a New Family of Bacterial Lipases

ABSTRACT We cloned lipG, which encoded a lipolytic enzyme, from a Korean tidal flat metagenomic library. LipG was related to six putative lipases previously identified only in bacterial genome sequences. These enzymes comprise a new family. We partially characterized LipG, providing the first experimental data for a member of this family.

Nocardioides dubius sp. nov., isolated from an alkaline soil

A Gram-positive, rod- or coccus-shaped bacterial strain, KSL-104(T), was isolated from an alkaline soil from Korea and its taxonomic position was investigated by a polyphasic approach. Strain KSL-104(T) grew optimally at pH 7.0-8.0 and 30 degrees C. It was characterized chemotaxonomically as having a cell-wall peptidoglycan type based on ll-2,6-diaminopimelic acid with MK-8(H(4)) as the predominant menaquinone. The major fatty acid was iso-C(16:0) and the major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol. The DNA G+C content was 70.6 mol%. A neighbour-joining phylogenetic tree based on 16S rRNA gene sequences revealed that strain KSL-104(T) joined the cluster comprising Nocardioides jensenii and Marmoricola aurantiacus. The cellular fatty acid profile of strain KSL-104(T) was different from that of M. aurantiacus. Strain KSL-104(T) and the type strain of N. jensenii exhibited a 16S rRNA gene sequence similarity value of 97.1% and a mean DNA-DNA relatedness value of 13%. Levels of 16S rRNA gene sequence similarity between strain KSL-104(T) and the type strains of other Nocardioides species were in the range 94.0-96.5%. On the basis of phenotypic, phylogenetic and genetic data, strain KSL-104(T) (=KCTC 9992(T)=JCM 13008(T)) represents a novel species of the genus Nocardioides, for which the name Nocardioides dubius sp. nov. is proposed.

Metabolomics-Based Chemotaxonomic Classification of Streptomyces spp. and Its Correlation with Antibacterial Activity.

Secondary metabolite-based chemotaxonomic classification of Streptomyces (8 species, 14 strains) was performed using ultraperformance liquid chromatography-quadrupole-time-offlight- mass spectrometry with multivariate statistical analysis. Most strains were generally well separated by grouping under each species. In particular, S. rimosus was discriminated from t he r emaining s ev en s pecies ( S. coelicolor, S. griseus, S. indigoferus, S. peucetius, S. rubrolavendulae, S. scabiei, and S. virginiae) in partial least squares discriminant analysis, and oxytetracycline and rimocidin were identified as S. rimosus-specific metabolites. S. rimosus also showed high antibacterial activity against Xanthomonas oryzae pv. oryzae , the pathogen responsible for rice bacterial blight. This study demonstrated that metabolite-based chemotaxonomic classification is an effective tool for distinguishing Streptomyces spp. and for determining their species-specific metabolites.