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A cyclodipeptide synthase-containing gene cluster ( pcm ) was identified in Streptomyces chrestomyceticus NA4264 through genome mining. Heterologous expression of the cryptic pcm gene cluster in Streptomyces albus led to the production of a new highly modified cyclodipeptide named purincyclamide ( 1 ). Bioinformatic analysis and gene knockout experiments revealed the biosynthetic pathway. The production of 1 was achieved through a one-pot enzymatic reaction.

Three new phenazine-type compounds, named phenazines SA-SC (1-3), together with four new natural products (4-7), were isolated from the fermentation broth of an earwig-associated Streptomyces sp. NA04227. The structures of these compounds were determined by extensive analyses of NMR, high resolution mass spectroscopic data, as well as single-crystal X-ray diffraction measurement. Sequencing and analysis of the genome data allowed us to identify the gene cluster (spz) and propose a biosynthetic pathway for these phenazine-type compounds. Additionally, compounds 1-5 exhibited moderate inhibitory activity against acetylcholinesterase (AChE), and compound 3 showed antimicrobial activities against Micrococcus luteus., (Copyright © 2019 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.)

Genome mining of the marine Streptomyces seoulensis A01 enabled the identification of a giant type I polyketide synthase gene cluster ( asm). Heterologous expression of the cryptic asm cluster using a bacterial artificial chromosome vector in heterologous host led to the production of ansaseomycins A (1) and B (2). A plausible biosynthetic pathway was also proposed. Additionally, compounds 1 and 2 are active against K562 cell lines with IC 50 values of 13.3 and 18.1 μM, respectively.

Mayamycin B, a new antibacterial type II polyketide, together with its known congener mayamycin A, were isolated from Streptomyces sp. 120454. The structure of new compound was elucidated by extensive spectroscopic analysis and comparison with literature data. Sequencing and bioinformatics analysis revealed the biosynthetic gene cluster for mayamycins A and B.

Two new alkaloids, strepchazolins A ( 1 ) and B ( 2 ), together with a previously reported compound, streptazolin ( 3 ), were isolated from a marine actinomycete, Streptomyces chartreusis NA02069, collected in the Coast of Hainan Island, China. The structures of new compounds were determined by extensive NMR, mass spectroscopic and X-ray crystallographic analysis, as well as modified Mosher's method. Compound 1 showed weak anti- Bacillus subtilis activity with the MIC value of 64.0 μM, and weak inhibitory activity against acetylcholinesterase (AChE) in vitro with IC 50 value of 50.6 μM, while its diastereoisomer, Compound 2 , is almost inactive., Competing Interests: The authors declare no conflict of interest.

The conversion from triene- to diene-typed ansamycins is clarified step by step in Streptomyces seoulensis IFB-A01. Such an intertype convertibility is adopted to establish for the first time the simultaneous mutasynthesis of both types of C17-benzene ansamycins (C17BAs). Three of the newly generated unnatural compounds showed potent cytotoxicity.

A new alkaloid was isolated from the ethyl acetate extract of the culture of a termite-associated Streptomyces koyangensis BY-4. The structure of 1 was elucidated by using MS, NMR, electronic circular dichroism data, and computational approaches. Compound 1 showed weak antimicrobial activities against a panel of test microbes.

Most eubacteria contain highly conservative gene clusters in the adjacent regions of oriC. According to this principle, a 1.4 kb DNA fragment containing parts of dnaA and dnaN genes of Streptomyces avermitilis was cloned by degenerate PCR. Sequence analysis of this fragment indicated that it encoded two partial genes in the order dnaA (the putative initiator protein) and dnaN (the beta subunit of DNA polymerase III). The intergenic non-coding region between dnaA and dnaN was found to contain 19 putative DnaA boxes, i.e. 9 nt long DnaA protein recognition sequences. It was confirmed that the location, orientation and spacing of DnaA boxes in this intergenic region are conserved among Streptomyces. The consensus sequence of DnaA box identified is (T/C)(T/C)(G/A/C)TCCACA (preferred bases in italic). When this fragment was cloned into Escherichia coli plasmid pQC156, which is otherwise non-replicative in Streptomyces, it exhibited autonomous replication activity in Streptomyces lividans, a closely related Streptomyces strain. Different parts of the oriC contribute unequally to the stability and transformation efficiency. The 3' region of oriC may contain features that support stable autonomous replication. The implications of these results for the understanding of the S. avermitilis oriC replication initiation process and its future application are discussed.

• Murayaquinones B-E (1 – 4) were isolated from an insect derived actinobacterium. • Structures of new compounds were elucidated by analysis their spectroscopic data. • Murayaquinone D exhibited cytotoxic activities against six cancer cell lines. Chemical study of the insect-derived bacterium, Streptomyces sp. NA4286, led to the discovery of four new polyketides, murayaquinones B-E (1 – 4), together with a known compound, murayaquinone (5). The structures of new compounds (1 – 4) were determined by extensive analysis of their NMR and HRESIMS data. The absolute configuration of (+)- 1 and (−)- 1 was assigned through comparison of experimental and calculated ECD spectra. Murayaquinone D (3) exhibited potent cytotoxic activities against six human cancer cell lines with IC 50 values ranging from 1.03 to 9.99 μM. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • New borrelidin-type macrolactones were isolated from an endophyte. • The structures of new compounds were elucidated by spectroscopic data. • Borrelidin A showed potent activity against M. luteus with MIC value of 1.0 μM. Abstract Three new borrelidin-type macrolactones, designated as borrelidins J−L (4 – 6), together with borrelidin A (1), borrelidin E (2), and 12-desnitrile-12-carboxyl-borrelidin (3) were isolated from a plant endophytic Streptomyces sp. NA06554. Their structures were determined by extensive spectroscopic analysis including HRESIMS, 1D and 2D NMR data. The antibacterial activities for compounds 1 – 6 were examined. Borrelidins A (1) and L (6) showed potent and moderate antibacterial activity against Micrococcus luteus , respectively, whereas other derivatives (2 – 5) are almost inactive, which allows us to propose a plausible structure-activity relationship. [ABSTRACT FROM AUTHOR]

[Display omitted] Salinopyridins A and B, two novel polyethers containing a rare pyridine moiety, were isolated from an earwig symbiotic Streptomyces sp. NA4227. Their structures were determined by extensive spectroscopic analysis. Based on the structure, bioinformatics analysis and gene mutation experiments, we proposed that salinopyridins share the same biosynthetic pathway with salinomycin, and the formation of pyridine moiety is assembled through a nonenzymatic process. Salinopyridins A and B exhibited potent activity against several Gram-positive bacteria. [ABSTRACT FROM AUTHOR]