Streptomycetes are a rich source of bioactive specialized metabolites, including several examples of the rapidly growing class of ribosomally-biosynthesized and post-translationally-modified peptide (RiPP) natural products. Here we report the discovery from Streptomyces sp. FXJ1.264 of azolemycins A–D, a complex of novel linear azole-containing peptides incorporating a unique oxime functional group. Bioinformatics analysis of the Streptomyces sp. FXJ1.264 draft genome sequence identified a cluster of genes that was hypothesized to be responsible for elaboration of the azolemycins from a ribosomally-biosynthesized precursor. Inactivation of genes within this cluster abolished azolemycin production, consistent with this hypothesis. Moreover, mutants lacking the azmE and azmF genes accumulated azolemycin derivatives lacking the O-methyl groups and an amino group in place of the N-terminal oxime (as well as proteolysed derivatives), respectively. Thus AzmE, a putative S-adenosyl methionine-dependent methyl transferase, is responsible for late-stage O-methylation reactions in azolemycin biosynthesis and AzmF, a putative flavin-dependent monooxygenase, catalyzes oxidation of the N-terminal amino group in an azolemycin precursor to the corresponding oxime. To the best of our knowledge, oxime formation is a hitherto unknown posttranslational modification in RiPP biosynthesis.

The draft genome sequence of marine Streptomyces olivaceus strain FXJ 7.023 contains a cryptic Type III polyketide synthase (type III PKS) gene cluster, which is similar to the Streptomyces coelicolor THN biosynthesis gene cluster. A putative type III PKS (SoRppA) gene and its adjacent gene for cytochrome P450 158A2 (SoCYP158A2) of this gene cluster were cloned by PCR screening through a fosmid genomic library of S. olivaceus FXJ 7.023. Tandem expression of SoRppA and SoCYP158A2 in Escherichia coli strain BL21 (DE3) plysS resulted in obvious biosynthesis of phenol and indole, while heterologous expression of SoRppA or SoCYP158A2 alone did not. The engineered strain sorppAcyp158a2BL21 showed tolerance to phenol concentration up to 0.75 g/L. Continuous biosynthesis of phenol and indole by the immobilized engineered strain on macroporousresin was achieved, and the productivities of phenol and indole in extractant-free culture in 102 h were 0.08 and 1.525 g/L/h, respectively, with the highest production reached 0.67 and 14.48 g/L, respectively. These results suggest that the engineered strain and immobilized continuous fermentation process may provide potential for “green” production of phenol and indole.

A novel endophytic actinomycete, designated strain KLBMP 1483T, was isolated from the stem of the coastal plant Dendranthema indicum (Linn.) Des Moul collected from Nantong, in East China. Phylogenetic analysis showed that strain KLBMP 1483T was affiliated with the genus Glycomyces within the family Glycomycetaceae and shared the highest 16S rRNA gene sequence similarities with the type strains of Glycomyces arizonensis NRRL B-16153T (96.7%) and Glycomyces tenuis IFO 15904T (96.2%), and lower similarities (94.1–95.1%) to the other members of the genus Glycomyces, which distinguished KLBMP 1483T from representatives of the genus Glycomyces. The whole-cell hydrolysates contained meso-diaminopimelic acid, glucose, xylose and galactose. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides, two unknown aminophospholipids, two phosphoglycolipids, two unknown phospholipids and one unknown lipid. MK-10(H4) was the predominant menaquinone. The major fatty acids were iso-C15:0, anteiso-C15:0, iso-C16:0, iso-C16:1 G and anteiso-C17:0. On the basis of the phenotypic and genotypic characteristics presented in this study, strain KLBMP 1483T represents a novel species, for which the name Glycomyces phytohabitans sp. nov. is proposed. The type strain is KLBMP 1483T (NBRC 109116T=DSM 45766T).

The anthrabenzoxocinones (ABXs) are hexacyclic aromatic compounds with various bioactivities. Some ABXs with two stereogenic carbon centers have been isolated from different actinomycetes. However, none of them have an absolute configuration assigned, which precludes further studies on the structure–activity relationship and biosynthetic mechanisms of the ABXs. An ABX compound 1.264-C was isolated from Streptomyces sp. FXJ1.264. The absolute configuration of 1.264-C was characterized by X-ray crystallographic, electronic, and experimental circular dichroism (CD) analyses. Based on the reported CD and specific rotation data, the absolute configurations of several other ABXs were also assigned.(6S,16S)-3,11,13,15-Tetrahydroxy-1,6,9,9-tetramethyl-9,16-dihydro-6H-6,16-epoxyanthra[2,3-e]benzo[b]oxocin-14(7H)-oneC27H24O7[α]D23=+375.4 (c 0.013, CH2Cl2)Source of chirality: natural product from Streptomyces sp. FXJ1.264Absolute configuration: (6S,16S)

A novel actinomycete strain, designated TRM 40133T, was isolated from a hypersaline habitat of Tarim basin in Xinjiang Province, north-west China. Its taxonomic status was determined using a polyphasic approach. Phylogenetic analysis based on an almost-complete 16S rRNA gene sequence of the strain showed that it formed a well-seperated sub-branch within the radiation of the genus Saccharopolyspora. The highest levels of 16S rRNA gene sequence similarity was found between the strain TRM 40133T and Saccharopolyspora qijiaojingensis YIM 91168T (96.5%). The chemotaxonomic characteristics of the isolate are typical for the genus Saccharopolyspora. It contained meso-DAP as the diagnostic diamino acid. Whole cell hydrolysate contained arabinose, xylose, ribose and glucose. The diagnostic phospholipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylinositol and two unknown phospholipids. The main menaquinone was MK-9(H6) and MK-9(H4). No mycolic acid was detected. The predominant cellular fatty acids were iso-C16:0 and anteiso-C17:0. The G+C content of the genomic DNA was 68.2 mol%. In addition, the strain TRM 40133T had a phenotypic profile that readily distinguished it from the recognized representatives of the genus Saccharopolyspora. The strain TRM 40133T therefore represents a novel species of the genus Saccharopolyspora, for which the name Saccharopolyspora lacisalsi sp. nov. is proposed. The type strain is TRM 40133T (=KCTC 19987T =CCTCC AA 2010012T).

Systematics can provide a fundamental framework for understanding the relationships and diversification of organisms. Multilocus sequence analysis (MLSA) has shown great promise for an elaborate taxonomic grouping of streptomycete diversity. To evaluate the practical significance of MLSA as a valuable systematic tool for streptomycetes, we examined six endophytic Streptomyces griseus isolates and two S. griseus reference strains possessing obvious antagonistic activities and identical 16S rRNA gene sequences, using both housekeeping genes and secondary metabolic genes. All the eight strains contained PKS-I and NRPS genes, but not PKS-II genes, and showed similar diversity in both the MLSA phylogeny based on five housekeeping genes (atpD, gyrB, recA, rpoB and trpB) and fingerprinting of KS-AT genes. We also inferred a phylogeny based on concatenated amino acid sequences of representative KS-AT genes from the strains, which displayed a topology correlated well with those of housekeeping-gene MLSA and KS-AT fingerprinting. The good congruence observed between phylogenies based on the different datasets verified that the MLSA scheme provided robust resolution at intraspecific level and could predict the overall diversity of secondary metabolic potential within a Streptomyces species, despite somewhat of a discrepancy with antimicrobial data. It is therefore feasible to apply MLSA to dissecting natural diversity of streptomycetes for a better understanding of their evolution and ecology, as well as for facilitating their bioprospecting.

Two Gram-positive, rod-shaped bacterial strains, H101T and H207, were isolated from deep sea water collected from South-West Indian Ocean. Phylogenetic analysis of 16S rRNA gene sequences showed that the two strains were closely related to one another (100% similarity), and had the closest relationship with Microbacterium hominis NBRC 15708T and Microbacterium insulae KCTC 19247T (98.2–98.3% similarities). DNA–DNA hybridization value between strains H101T and H207 was 87.2 ± 3.7%, and the values between the two strains and the closely related type strains were well below 70%. The two strains also shared a number of physiological and biochemical characteristics that were distinct from the closely related species, and grew at 2–37 °C, pH 5–11 and 0–8% (w/v) NaCl. Both strains contained MK-12, MK-13 and MK-11 as the detected menaquinones. The peptidoglycan was of type B1γ with an interpeptide bridge D-Glu(Hyg) → Gly2 → l-Lys. The major cellular fatty acids were anteiso-C15:0, anteiso-C17:0, and iso-C16:0. Based on the genetic and phenotypic properties, it is proposed that strains H101T and H207 be classified as representatives of a novel species of the genus Microbacterium, with the name Microbacterium marinum sp. nov. The type strain is H101T (=CGMCC 4.6941T = DSM 24947T).

Streptomyces hygroscopicus and related species are the most well known candidate producers of antibiotics and many other industrially and agronomically important secondary metabolites in the genus Streptomyces. Multilocus sequence analysis (MLSA) has shown to be a powerful and pragmatic molecular method for unraveling streptomycete diversities. In this investigation, a multilocus phylogeny of 58 representatives of the S. hygroscopicus 16S rRNA gene clade including S. violaceusniger and related species was examined. The result demonstrated that the MLSA data were helpful in defining members of the S. hygroscopicus clade, providing further evidence that the MLSA scheme of five housekeeping genes (atpD, gyrB, recA, rpoB and trpB) is a valuable alternative for creating and maintaining operational protocols for the Streptomyces species assignment. DNA–DNA hybridization (DDH) between strains with representative MLSA evolutionary distances, combined with previous data from S. griseus and S. albidoflavus clades, revealed a high correlation between MLSA and DDH, and sustains that the five-gene nucleotide sequence distance of 0.007 could be considered as the species cut-off for the whole genus. This significant correlation thus makes the MLSA scheme applicable to construction of a theory-based taxonomy for both ecology and bioprospecting of streptomycetes. Based on the MLSA and DDH data, as well as phenotypic characteristics, 10 species and three subspecies of the S. hygroscopicus clade are considered to be later heterotypic synonyms of eight genomic species, and Streptomyces glebosus sp. nov., comb. nov. (type strain CGMCC 4.1873T = LMG 19950T = DSM 40823T) and Streptomyces ossamyceticus sp. nov., comb. nov. (type strain CGMCC 4.1866T = LMG 19951T = DSM 40824T) are also proposed.

The Streptomyces albidoflavus 16S rRNA gene clade contains 10 species and subspecies with identical 16S rRNA gene sequences and very similar numerical taxonomic data, including Streptomyces griseus subsp. solvifaciens. Type strains of this clade, as well as three CGMCC strains which were received as Streptomyces galilaeus, Streptomyces sioyaensis and Streptomyces vinaceus, respectively, that shared the same 16S rRNA gene sequences with the clade, were subjected to multilocus sequence analysis (MLSA), DNA–DNA hybridization (DDH) and phenotypic characterization for a comprehensive reevaluation. The 13 strains still formed a distinct, albeit loosely related, clade in the phylogenetic tree based on concatenated sequences of aptD, gyrB, recA, rpoB and trpB genes, supported by a high bootstrap value and different tree-making algorithms, with MLSA evolutionary distances ranging from 0 to 0.003. DDH values among these strains were well above the 70% cut-off point for species delineation. Based on the genotypic data of MLSA and DDH, combined with key phenotypic properties in common, it is proposed that the 10 species and subspecies of the S. albidoflavus clade, namely S. albidoflavus, S. canescens, S. champavatii, S. coelicolor, S. felleus, S. globisporus subsp. caucasicus, S. griseus subsp. solvifaciens, S. limosus, S. odorifer and S. sampsonii, should be merged into a single genomic species, for which the name S. albidoflavus is retained, and that the three strains S. galilaeus CGMCC 4.1320, S. sioyaensis CGMCC 4.1306 and S. vinaceus CGMCC 4.1305 should be assigned to S. albidoflavus as well. The results also indicated that MLSA could be the procedure of choice for distinguishing between species within Streptomyces 16S rRNA gene clades.

Streptomycetes are a rich source of bioactive specialized metabolites, including several examples of the rapidly growing class of ribosomally-biosynthesized and post-translationally-modified peptide (RiPP) natural products. Here we report the discovery from Streptomyces sp. FXJ1.264 of azolemycins A–D, a complex of novel linear azole-containing peptides incorporating a unique oxime functional group. Bioinformatics analysis of the Streptomyces sp. FXJ1.264 draft genome sequence identified a cluster of genes that was hypothesized to be responsible for elaboration of the azolemycins from a ribosomally-biosynthesized precursor. Inactivation of genes within this cluster abolished azolemycin production, consistent with this hypothesis. Moreover, mutants lacking the azmE and azmF genes accumulated azolemycin derivatives lacking the O-methyl groups and an amino group in place of the N-terminal oxime (as well as proteolysed derivatives), respectively. Thus AzmE, a putative S-adenosyl methionine-dependent methyl transferase, is responsible for late-stage O-methylation reactions in azolemycin biosynthesis and AzmF, a putative flavin-dependent monooxygenase, catalyzes oxidation of the N-terminal amino group in an azolemycin precursor to the corresponding oxime. To the best of our knowledge, oxime formation is a hitherto unknown posttranslational modification in RiPP biosynthesis.