Sattahipmycin, a Hexacyclic Xanthone Produced by a Marine-Derived Streptomyces.

Sattahipmycin was isolated from the mycelium of marine-derived Streptomyces sp. GKU 257-1 by following the antibiofilm activity against E. coli NBRC 3972 throughout the purification steps. The structure of sattahipmycin was determined to be a new polycyclic xanthone related to xantholipin but lacking a dioxymethylene and a chlorinated carbon. This compound showed activity toward Gram-positive bacteria and Plasmodium falciparum, antibiofilm formation of Escherichia coli, and cytotoxicity to human cancer cell lines. Using genome sequence data, a biosynthetic pathway leading to sattahipmycin has been proposed involving an uncharacterized type II polyketide synthase biosynthetic gene cluster.

Microbispora clausenae sp. nov., an endophytic actinobacterium isolated from the surface-sterilized stem of a Thai medicinal plant, Clausena excavala Burm. f.

An endophytic actinobacterium, strain CLES2T, was discovered from the surface-sterilized stem of a Thai medicinal plant, Clausena excavala Burm. f., collected from the Phujong-Nayoa National Park, Ubon Ratchathani Province, Thailand. The results of a polyphasic taxonomic study identified this strain as a member of the genus Microbispora and a Gram-stain-positive, aerobic actinobacterium. It had well-developed substrate mycelia, which were non-motile and possessed paired spores. A phylogenetic evaluation based on 16S rRNA gene sequence analysis placed this strain in the family Streptosporangiaceae, being most closely related to Microbispora bryophytorum NEAU-TX2-2T (99.4 %), Microbispora camponoti 2C-HV3T (99.2 %), Microbispora catharanthi CR1-09T (99.2 %) and Microbispora amethystogenes JCM 3021T and Microbispora fusca NEAU-HEGS1-5T (both at 99.1 %). The major cellular fatty acid of this strain was iso-C16 : 0 and major menaquinone was MK-9(H4). The polar lipid profile of strain CLES2T contained diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylinositol and phosphatidylinositol dimannosides. These chemotaxonomic data confirmed the affiliation of strain CLES2T to the genus Microbispora. The DNA G+C content of this strain was 70 mol%. Digital DNA-DNA hybridization and average nucleotide identity blast values between strain CLES2T and M. catharanthi CR1-09T were 62.4 and 94.0 %, respectively. The results of the polyphasic study allowed the genotypic and phenotypic differentiation of strain CLES2T from its closest species with valid names. The name proposed for the new species is Microbispora clausenae sp. nov. The type strain is CLES2T (=DSM 101759T=NRRL B-65340T).

Fodinicola acaciae sp. nov., an Endophytic Actinomycete Isolated from the Roots of Acacia mangium Willd. and Its Genome Analysis.

A novel endophytic actinomycete strain GKU 173T isolated from the roots of Acacia mangium Willd. showed potential plant growth promoting (PGP) activity. Phylogenetic analysis, based on 16S rRNA gene, indicated that strain GKU 173T was the most closely related to Fodinicola feengrottensis HKI 0501T-the only species in the genus Fodinicola. Morphology and chemotaxonomy of strain GKU 173T indicated that it belongs to the genus Fodinicola by having meso-diaminopimelic acid in the cell wall and xylose as the characteristic cell-wall sugars. The cellular fatty acid profile mainly comprised iso-C16:0, anteiso-C17:0, iso-C18:0, and iso-C17:0. The major menaquinones were MK-9(H4), MK-9(H6), and MK-9(H8). The main polar phospholipids contained diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), and phosphatidylinositol (PI). Genome analysis signified DNA G+C content of 67.81 mol%. The level of digital DNA-DNA relatedness between strain GKU 173T and the type strain was 21.30%. On the basis of polyphasic characteristics, strain GKU 173T clearly represents a novel species of the genus Fodinicola, for which the name Fodinicola acaciae sp. nov. (= TBRC 10620T = NBRC 114213T) is proposed. Furthermore, genome analysis of both strains suggested that members of the genus Fodinicola are promising sources of beneficial PGP-actinomycetes and novel secondary metabolites.

Sarpeptins A and B, Lipopeptides Produced by Streptomyces sp. KO-7888 Overexpressing a Specific SARP Regulator.

Whole genome analysis of Streptomyces sp. KO-7888 has revealed various pathway-specific transcriptional regulatory genes associated with silent biosynthetic gene clusters. A Streptomyces antibiotic regulatory protein gene, speR, located adjacent to a novel nonribosomal peptide synthetase (NRPS) gene cluster, was overexpressed in the wild-type strain. The resulting recombinant strain of Streptomyces sp. KO-7888 produced two new lipopeptides, sarpeptins A and B. Their structures were elucidated by high-resolution electrospray ionization mass spectrometry, NMR analysis, and the advanced Marfey's method. The distinct modular sections of the corresponding NRPS biosynthetic gene cluster were characterized, and the assembly line for production of the lipopeptide chain was proposed.

Bisoxazolomycin A: a new natural product from 'Streptomyces subflavus subsp. irumaensis' AM-3603.

Bisoxazolomycin (1), oxazolomycin A2 (2) and oxazolomycin A (3) were identified by physicochemical screening approach from a culture broth of 'Streptomyces subflavus subsp. irumaensis' AM-3603. Compound 2 is a hydrolyzed analog of 3 at the ß-lactone ring, and 1 is a new dimeric analog of 2. Compounds 1 and 2 exhibited less potent antibacterial activity and cytotoxicity than 3, which might be due to lack of the ß-lactone ring.