Summary auto-generated
Researchers isolated two novel actinobacterial strains from soil in Reed Flute Cave in China. Both strains (HKI 0119T and HKI 0120T) were Gram-positive, non-motile rod-shaped cells exhibiting a distinctive rod-to-coccus growth cycle. They shared similar cell wall chemistry, including meso-diaminopimelic acid in their peptidoglycan and MK-8(H4) as their major respiratory quinone, with DNA G+C content of 68-69 mol%. Phylogenetic analysis of 16S rDNA sequences positioned these isolates between the genera Janibacter and Tetrasphaera but showed significant differences in morphology, physiology, and chemotaxonomy from both neighboring genera. DNA-DNA hybridization revealed only 29.2% relatedness between the two strains, supporting their classification as separate species. Based on these findings, the researchers established a new genus, Knoellia, containing two species: Knoellia sinensis and Knoellia subterranea, each represented by single type strains from the cave environment.
Key findings
- Two novel actinobacterial species were isolated from cave soil in China and placed in a new genus Knoellia based on phylogenetic and chemotaxonomic analysis
- The isolates exhibited a unique rod-coccus growth cycle and possessed meso-diaminopimelic acid peptidoglycan and MK-8(H4) menaquinone, but differed significantly from phylogenetically related genera Janibacter and Tetrasphaera
- DNA-DNA hybridization showed only 29.2% relatedness between the two strains, justifying their classification as two distinct species: K. sinensis and K. subterranea
- The two Knoellia species showed distinguishing physiological differences including temperature tolerance, antibiotic susceptibility, and substrate utilization patterns
- K. sinensis cannot grow at 37°C while K. subterranea tolerates this temperature, and they differ in their ability to decompose various organic compounds and utilize specific carbon sources
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Abstract
Two novel strains of the class Actinobacteria were isolated from a cave in China. Cells of both strains were Gram-positive, non-motile, non-spore-forming and not acid-fast and exhibited a rod/coccus growth cycle. Both isolates grew well on complex organic media under aerobic conditions. Their cell wall peptidoglycan contained meso-diaminopimelic acid as diagnostic diamino acid. The acyl type of the glycan chain of peptidoglycan was acetyl. The major respiratory quinone was MK-8(H(4)). The cellular fatty acid profile was characterized by the predominance of 13-methyltetradecanoic (i-C(15:0)), 15-methylhexadecanoic (i-C(17:0)), 14-methylpentadecanoic (i-C(16:0)) and 14-methylhexadecanoic (ai-C(17:0)) acids. The major polar lipids were phosphatidylethanolamine, phosphatidylinositol and diphosphatidylglycerol. Mycolic acids were absent. The DNA G+C composition was 68--69 mol%. 16S rDNA-based phylogenetic analysis revealed an intermediate phylogenetic position of the cave isolates between the genera Janibacter and Tetrasphaera, which did not permit their unambiguous affiliation to either genus. Differences in morphological, physiological and chemotaxonomic properties between the two isolates and their closest phylogenetic neighbours support the proposal of a new genus and two novel species, Knoellia sinensis gen. nov., sp. nov. and Knoellia subterranea sp. nov. The type and only strains of the species are respectively HKI 0119(T) (=DSM 12331(T)=CIP 106775(T)) and HKI 0120(T) (=DSM 12332(T)=CIP 106776(T)).