Summary auto-generated
This polyphasic taxonomic study clarified relationships among thermophilic alkalitolerant streptomycetes isolated from soil. DNA–DNA relatedness studies and 16S rDNA sequencing confirmed that Streptomyces thermodiastaticus, S. thermoviolaceus, and S. thermovulgaris are distinct species. However, the researchers found that S. thermonitrificans represents a later subjective synonym of S. thermovulgaris, based on genotypic and phenotypic evidence. Ten of eleven thermophilic alkalitolerant isolates were classified as S. thermovulgaris. One isolate, strain TA56, merited species status as a novel taxon. The authors propose the name Streptomyces thermoalcalitolerans sp. nov. for this strain. Additionally, a neutrophilic thermophilic isolate, strain NAR85, was identified as S. thermodiastaticus. The study used multiple methods including morphological analysis, chemotaxonomy, DNA–DNA hybridization, 16S rRNA gene sequencing, ribotyping, and degradation tests to establish these taxonomic relationships.
Key findings
- S. thermonitrificans is a later subjective synonym of S. thermovulgaris based on DNA–DNA relatedness values and identical 16S rDNA sequences
- Streptomyces thermoalcalitolerans sp. nov. (strain TA56) is proposed as a new thermophilic alkalitolerant species distinct from existing thermophilic taxa
- S. thermodiastaticus, S. thermoviolaceus, and S. thermovulgaris are confirmed as three separate genomic species despite their close phylogenetic relationships
- Ten of eleven thermophilic alkalitolerant isolates from soil samples belong to S. thermovulgaris, demonstrating its prevalence among naturally occurring thermophilic streptomycetes
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Abstract
A polyphasic taxonomic study was undertaken to clarify relationships within and between representative thermophilic alkalitolerant streptomycetes isolated from soil and appropriate marker strains. The resultant data, notably those from DNA-DNA relatedness studies, support the taxonomic integrity of the validly described species Streptomyces thermodiastaticus, Streptomyces thermoviolaceus and Streptomyces thermonvulgaris. However, the genotypic and phenotypic data clearly show that Streptomyces thermonitrificans Desai and Dhala 1967 and S. thermovulgaris (Henssen 1957) Goodfellow et al. 1987 represent a single species. On the basis of priority, S. thermonitrificans is a later subjective synonym of of S. thermovulgaris. Similarly, 10 out of the 11 representative thermophilic alkalitolerant isolates had a combination of properties consistent with their classification as S. thermovulgaris. The remaining thermophilic alkalitolerant isolate, Streptomyces strain TA56, merited species status. The name Streptomyces thermoalcalitolerans sp. nov. is proposed for this strain. A neutrophilic thermophilic isolate, Streptomyces strain NAR85, was identified as S. thermodiastaticus.