Summary auto-generated
Researchers isolated a novel actinomycete bacterium from soil collected in a gold mine cave near Kongju, Republic of Korea. Through 16S ribosomal DNA sequence analysis and chemotaxonomic characterization, they determined this isolate belonged to the genus Pseudonocardia. The organism possessed characteristic features including type IV cell wall with meso-diaminopimelic acid, arabinose and galactose; MK-8(H4) as the major menaquinone; phospholipid type PIII pattern; and 71 mol% DNA G-C content. Phylogenetically, the strain branched between two existing Pseudonocardia species clusters with 99% bootstrap support. The isolate differed from known Pseudonocardia species in specific phospholipids, fatty acid profiles, and physiological properties including weak acid production from fructose and glycerol, and distinctive substrate mycelium coloration. DNA-DNA hybridization showed low relatedness to closest relatives (14-32%), confirming it represented a distinct species. The combination of unique physiological, cellular, and genetic characteristics distinguished this organism from all validly published Pseudonocardia species.
Key findings
- A new Pseudonocardia species, P. kongjuensis, was isolated from a Korean gold mine cave and characterized using 16S rDNA sequencing and chemotaxonomic analysis.
- The strain possessed type IV cell wall chemistry, MK-8(H4) menaquinone, and phospholipid type PIII pattern characteristic of the genus Pseudonocardia with 71 mol% DNA G-C content.
- The isolate demonstrated unique combinations of phospholipids and fatty acids, including presence of phosphatidylethanolamine and specific branched fatty acids absent in related species.
- DNA-DNA hybridization revealed low relatedness (14-32%) to phylogenetically closest species P. compacta and P. autotrophica, supporting species status.
- Physiological testing differentiated the new species by distinctive acid production patterns, particularly weak reactions with fructose and glycerol compared to related Pseudonocardia species.
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Abstract
The taxonomic position of an isolate that was recovered from a gold mine cave near Kongju, Republic of Korea, was determined by 16S rDNA sequence studies and chemotaxonomic characterization. Comparative studies of 16S rDNA sequences indicated that this organism was phylogenetically related to members of the genus Pseudonocardia, branching outside a cluster encompassing Pseudonocardia autotrophica and Pseudonocardia compacta. The affiliation to the genus was also supported by the cell chemistry, which was represented by a type IV cell wall, MK-8(H(4)) as the major menaquinone, a phospholipid type PIII pattern (phosphatidylcholine as a diagnostic phospholipid) and a DNA G+C content of 71 mol%. The fatty acid profile contained saturated, unsaturated and 10-methyl branched fatty acids, but tuberculostearic acid and hydroxy fatty acids were not present. The isolate differed from its phylogenetic neighbours in the presence of phosphatidylethanolamine, dodecanoate, 16-methylheptadecenoate and 16-methylheptadecanoate and the absence of phosphatidylinositol mannoside and phosphatidylmethylethanolamine. The unique combination of physiological properties, the cellular fatty acid profile and DNA--DNA hybridization data indicates that this organism is readily differentiated from the type strains of all of the validly published species of the genus Pseudonocardia. The name Pseudonocardia kongjuensis sp. nov. is proposed for the type strain, LM 157(T) (=IMSNU 50583(T)=KCTC 9990(T)=DSM 44525(T)).