Streptomonospora alba sp. nov., a novel halophilic actinomycete, and emended description of the genus Streptomonospora Cui et al. 2001

Researchers isolated a novel halophilic actinomycete, strain YIM 90003T, from hypersaline soil in Xinjiang Province, China. The organism was cultured on starch-casein agar supplemented with 20% salt. Microscopic examination revealed white aerial mycelium forming short spore chains with wrinkled, non-motile spores, and well-developed substrate mycelium. Chemical analysis identified meso-diaminopimelic acid in the peptidoglycan, with galactose and arabinose as cell-wall sugars. Menaquinone composition varied with growth medium, consisting primarily of MK-9 and MK-10 variants. The strain contained complex phospholipids and had a DNA G+C content of 74.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing showed 99.3% similarity to Streptomonospora salina, but DNA-DNA hybridization yielded only 18% relatedness, confirming genomic distinctness. The organism differed from S. salina in oxidase negativity, melanin non-production, and physiological characteristics. Based on these findings, strain YIM 90003T was designated as Streptomonospora alba sp. nov. Additionally, the genus description of Streptomonospora was amended to clarify that peptidoglycan contains exclusively meso-diaminopimelic acid as the diagnostic diamino acid.

Key findings

• Streptomonospora alba sp. nov. is a novel halophilic actinomycete isolated from hypersaline soil in western China, representing a new species within the genus Streptomonospora
• DNA-DNA hybridization showed only 18% relatedness between the new strain and the phylogenetically similar S. salina (99.3% 16S rRNA similarity), confirming species distinctness
• The genus Streptomonospora description was emended to specify that peptidoglycan contains exclusively meso-diaminopimelic acid, correcting previous descriptions that listed additional amino acids later determined to be contaminating proteins
• Menaquinone composition varies with growth medium, with MK-9(H4) predominating in glucose-yeast extract medium and MK-10(H2), MK-9(H8), and MK-10(H4) in vitamin-enriched medium
• The new species differs from S. salina in oxidase activity, melanin production, and starch hydrolysis capability