Summary auto-generated
This study examined neutrotolerant acidophilic actinomycetes isolated from soil using polyphasic taxonomy. Two representative strains—JL164 from UK podsol soil and CN732T from Korean forest soil—were analyzed using morphological, chemotaxonomic, and molecular methods including 16S rRNA gene sequencing. Both strains were assigned to the genus Streptomyces based on their characteristics: extensively branched mycelia, arthrospore chains, LL-diaminopimelic acid in cell walls, and menaquinones with nine isoprene units. Strain JL164 clustered closely with Streptomyces mirabilis (99.6% 16S rRNA similarity), while CN732T formed a distinct phyletic line, sharing only 97.1-97.2% similarity with its nearest relatives. The study proposes CN732T and related cluster 13 members as a novel species, Streptomyces yeochonensis sp. nov., isolated from acidic soil in Yeochon, Korea. The organism grows at pH 4.3-7.3 and utilizes various organic compounds. Findings demonstrate that neutrotolerant acidophilic actinomycetes are taxonomically diverse within the genus Streptomyces, distinct from strictly acidophilic members classified in Streptacidiphilus.
Key findings
- Two neutrotolerant acidophilic actinomycete strains were reclassified within genus Streptomyces using 16S rRNA gene sequencing and polyphasic taxonomy.
- Strain CN732T forms a distinct phyletic line in the Streptomyces tree with only 97.1% 16S rRNA similarity to nearest relatives, warranting description as a novel species.
- Streptomyces yeochonensis sp. nov. is proposed for CN732T and related cluster 13 members, isolated from acidic Korean forest soil.
- Strain JL164 shows 99.6% 16S rRNA gene similarity to S. mirabilis type strain, indicating close relationship with existing species.
- Neutrotolerant acidophilic actinomycetes represent a taxonomically heterogeneous group distinct from strictly acidophilic Streptacidiphilus species.
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Abstract
Acidophilic actinomycete strains that represent the two major neutrotolerant clusters defined by numerical taxonomy (Seong, 1992) were the subject of a polyphasic taxonomic study. The centrotypes of each cluster, designated as strain JL164 (=KCTC 9924) of cluster 21 and strain CN732T (=KCTC 9926T=IMSNU 50114T=NRRL B-24245T) of cluster 13, were assigned initially to the genus Streptomyces on the basis of morphological and chemotaxonomic characteristics; this assignation was confirmed by 16S rRNA gene sequence data. Strain CN732T formed a distinct phyletic line within the Streptomyces tree, whereas strain JL164 was related closely to the type strain of Streptomyces mirabilis. It is evident from the present and previous studies that neutrotolerant acidophilic actinomycetes comprise taxonomically diverse groups within the variation encompassed by the genus Streptomyces. It is also apparent that strain CN732T and other members of cluster 13 merit recognition as a novel species, for which the name Streptomyces yeochonensis sp. nov. is proposed.