Saccharopolyspora antibiotica sp. nov. and Micromonospora mangrovicola sp. nov., the new actinomycetes isolated from mangrove sediments

Two novel actinomycetes, designated strains MS10ᵀ and MS34ᵀ, were isolated from marine sediment collected at the Nature Education Center for Mangrove Conservation and Ecotourism, Chonburi Province, Thailand. Strain MS10ᵀ exhibited 98.8% 16S rRNA gene sequence similarity to <i>Saccharopolyspora gloriosae</i> YIM 60513ᵀ, while strain MS34ᵀ shared 99.3% similarity with <i>Micromonospora narathiwatensis</i> DSM 45248ᵀ. MS10ᵀ showed morphological and chemotaxonomic features consistent with the genus <i>Saccharopolyspora</i>, including aerial mycelia with chains of cylindrical spores, <i>meso</i>-diaminopimelic acid in the cell wall and whole-cell sugars included ribose, arabinose, glucose and galactose. Its major menaquinones were MK-9(H₄), MK-9(H₆) and MK-9(H₁₀); the fatty acid profile was dominated by C_₁₆:₀, anteiso-C_₁₇:₀ and C_₁₇:₀ 10-methyl. MS34ᵀ exhibited typical characteristics of <i>Micromonospora</i>, forming monomeric spores on substrate mycelia without aerial structures. Its chemotaxonomic profile included <i>meso</i>-diaminopimelic acid; whole-cell sugars included rhamnose, ribose, xylose, arabinose and glucose; and menaquinones MK-9(H₄), MK-9(H₆) and MK-9(H₁₀). The major fatty acids were anteiso-C_₁₅:₀, iso-C_₁₅:₀ and C_₁₇:₀ 10-methyl. Genome-based comparisons revealed digital DNA-DNA hybridization and average nucleotide identity values below the accepted thresholds for species delineation relative to the closest type strains. These results support the conclusion that strains MS10ᵀ and MS34ᵀ represent two novel species. The names <i>Saccharopolyspora antibiotica</i> sp. nov. (type strain=TBRC 19727ᵀ=NBRC 117248ᵀ) and <i>Micromonospora mangrovicola</i> sp. nov. (type strain=TBRC 19729ᵀ=NBRC 117249ᵀ) are proposed.