sp. nov. and sp. nov., two novel actinobacteria isolated from rhizosphere soil with broad-spectrum antifungal activity.

Two actinobacterial strains, designated NEAU-383 and NEAU-Y11, exhibiting antifungal activity, were isolated from the rhizosphere soil of plants in Harbin, Heilongjiang Province, and Guangzhou, Guangdong Province, respectively. Both strains formed short, wrinkled, spiral spore chains on aerial hyphae. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strains NEAU-383 and NEAU-Y11 were most closely related to HM 35, NRRL B-5491 and CA1R205. However, digital DNA-DNA hybridization values between the two strains and their close relatives (27.1% between the two strains; 27.5-59.0% for NEAU-383; 27.0-39.8% for NEAU-Y11) fell below the 70% species delineation threshold. The genomic G+C contents were 71.0 mol% for NEAU-383 and 70.5 mol% for NEAU-Y11. Both strains contained glucose and ribose as whole-cell sugars. The predominant menaquinones were MK-9(H) and MK-9(H), with NEAU-Y11 additionally containing MK-9(H). The major fatty acids (>10%) in both strains included iso-C, anteiso-C, iso-C and C, whilst iso-C was also a major component in NEAU-383. Both strains contained phosphatidylethanolamine and hydroxy-phosphatidylethanolamine as polar lipids. Additionally, NEAU-383 also possessed diphosphatidylglycerol, phosphatidylinositol, an unidentified ninhydride-positive lipid and five unidentified lipids, whereas NEAU-Y11 additionally contained two unidentified ninhydride-positive lipids and five unidentified lipids. Genomic analysis revealed that both strains possess abundant secondary metabolite biosynthesis gene clusters, including those for antibiotics, siderophores, polyketides and terpenoids, along with metabolic pathways associated with environmental adaptation. These findings provide insight into the potent antimicrobial activity exhibited by both strains. Based on genotypic, phenotypic and chemotaxonomic analyses, strains NEAU-383 and NEAU-Y11 represent two novel species within the genus , for which the names (type strain NEAU-383=JCM 36736=MCCC 1K08878) and (type strain NEAU-Y11=JCM 36418=MCCC 1K08681) are proposed.