Potential antibiotic production of Streptomyces justiciae sp. nov., isolated from the root of Justicia subcoriacea

Endophytic actinobacterial strain 3R004 T was isolated from a root of Justicia subcoriacea collected in Thailand. In this report, the taxonomic position of this strain is described using a polyphasic approach. Based on the morphological characteristics and chemical composition of its cells, strain 3R004 T was identified as a member of the genus Streptomyces . It produced a long chain of cylindrical spores on aerial mycelia. ll -Diaminopimelic acid was detected in the cell wall peptidoglycan. The menaquinones were MK-9(H 4 ), MK-9(H 6 ) and MK-9(H 8 ). C 16 : 0 , iso-C 16 : 0 , anteiso-C 15 : 0 and iso-C 15 : 0 were detected as the major cellular fatty acids. Polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and one unidentified lipid. Strain 3R004 T showed the highest 16S rRNA gene similarity of 99.45 % to Streptomyces cyaneochromogenes MK-45 T . The phylogenomic results indicated that strain 3R004 T was close to Streptomyces aquilus GGCR-6 T and Streptomyces antibioticus DSM 40234 T . The DNA–DNA hybridization and average nucleotide identity values among strain 3R004 T and closely related Streptomyces species were 35.5–63.1 % and 82.7–94.3 %, respectively. The type strain produced actinomycin D antibiotic as the major secondary metabolite. The maximum productivity of the actinomycin D (378 mg l −1 ) was observed when the strain was grown in 301 broth at 30 °C, 180 r.p.m. for 12 days. On the basis of phenotypic and genotypic evidence, strain 3R004 T represents a novel species of the genus Streptomyces , for which the name Streptomyces justiciae is proposed. The type strain is 3R004 T (=LMG 32138 T =TBRC 13128 T =NBRC 115065 T ).