The chemical examination of the solid cultures of the deep-sea-derived fungus Penicillium chrysogenum MCCC 3A00292 resulted in the isolation of three new versiol-type analogues, namely peniciversiols A–C (1–3), and two novel lactone derivatives, namely penicilactones A and B (6 and 7), along with 11 known polyketides. The planar structures of the new compounds were determined by the comprehensive analyses of the high-resolution electrospray ionization mass spectroscopy (HRESIMS) and nuclear magnetic resonance (NMR) data, while their absolute configurations were resolved on the basis of comparisons of the experimental electronic circular dichroism (ECD) spectra with the calculated ECD data. Compound 1 is the second example of versiols featuring a 2,3-dihydropyran-4-one ring. Additionally, compounds 6 and 7 are the first representatives of γ-lactone derivatives constructed by a 1,3-dihydroxy-5-methylbenzene unit esterifying with the α-methyl-γ-hydroxy-γ-acetic acid α,β-unsaturated-γ-lactone moiety and α-hydroxy-γ-methyl-γ-acetic acid α,β-unsaturated-γ-lactone unit, respectively. All of the isolated compounds were evaluated for their cytotoxic activities against five human cancer cell lines of BIU-87, ECA109, BEL-7402, PANC-1, and Hela-S3. Compound 1 exhibited a selective inhibitory effect against the BIU-87 cell line (IC₅₀ = 10.21 μM), while compounds 4, 5, 8, and 12–16 showed inhibitory activities against the ECA109, BIU-87, and BEL-7402 cell lines with the IC₅₀ values ranging from 7.70 to > 20 μM.

Griseoviridin (GV) and viridogrisein (VG, also referred as etamycin), both biosynthesized by a distinct 105 kb biosynthetic gene cluster (BGC) in Streptomyces griseoviridis NRRL 2427, are a pair of synergistic streptogramin antibiotics and very important in treating infections of many multi-drug resistant microorganisms. Three transporter genes, sgvT1–T3 have been discovered within the 105 kb GV/VG BGC, but the function of these efflux transporters have not been identified. In the present study, we have identified the different roles of these three transporters, SgvT1, SgvT2 and SgvT3. SgvT1 is a major facilitator superfamily (MFS) transporter whereas SgvT2 appears to serve as the sole ATP-binding cassette (ABC) transporter within the GV/VG BGC. Both proteins are necessary for efficient GV/VG biosynthesis although SgvT1 plays an especially critical role by averting undesired intracellular GV/VG accumulation during biosynthesis. SgvT3 is an alternative MFS-based transporter that appears to serve as a compensatory transporter in GV/VG biosynthesis. We also have identified the γ-butyrolactone (GBL) signaling pathway as a central regulator of sgvT1–T3 expression. Above all, overexpression of sgvT1 and sgvT2 enhances transmembrane transport leading to steady production of GV/VG in titers ≈ 3-fold greater than seen for the wild-type producer and without any notable disturbances to GV/VG biosynthetic gene expression or antibiotic control. Our results shows that SgvT1–T2 are essential and useful in GV/VG biosynthesis and our effort highlight a new and effective strategy by which to better exploit streptogramin-based natural products of which GV and VG are prime examples with clinical potential.

Background: Activation of silent biosynthetic gene clusters (BGCs) in marine-derived actinomycete strains is a feasible strategy to discover bioactive natural products. Actinoalloteichus sp. AHMU CJ021, isolated from the seashore, was shown to contain an intact but silent caerulomycin A (CRM A) BGC-cam in its genome. Thus, a genome mining work was preformed to activate the strain’s production of CRM A, an immunosuppressive drug lead with diverse bioactivities. Results: To well activate the expression of cam, ribosome engineering was adopted to treat the wild type Actinoalloteichus sp. AHMU CJ021. The initial mutant strain XC-11G with gentamycin resistance and CRM A production titer of 42.51 ± 4.22 mg/L was selected from all generated mutant strains by gene expression comparison of the essential biosynthetic gene-camE. The titer of CRM A production was then improved by two strain breeding methods via UV mutagenesis and cofactor engineering-directed increase of intracellular riboflavin, which finally generated the optimal mutant strain XC-11GUR with a CRM A production titer of 113.91 ± 7.58 mg/L. Subsequently, this titer of strain XC-11GUR was improved to 618.61 ± 16.29 mg/L through medium optimization together with further adjustment derived from response surface methodology. In terms of this 14.6 folds increase in the titer of CRM A compared to the initial value, strain XC-GUR could be a well alternative strain for CRM A development. Conclusions: Our results had constructed an ideal CRM A producer. More importantly, our efforts also had demonstrated the effectiveness of abovementioned combinatorial strategies, which is applicable to the genome mining of bioactive natural products from abundant actinomycetes strains.

Chemically investigating the marine-derived Streptomyces parvus 1268 led to the isolation of a new compound of carpatamide I (1). Subsequent genomic analysis identified its candidate biosynthetic gene cluster ctd of approximately 44 kb. In order to obtain more carpatamide derivatives, we conducted the upregulation of Ctd14, which is a positive regulator, and obtained improvement of carpatamide I and four new compounds of carpatamides J–M (2–5). The structures of the aforementioned five new isolates were identified by a combination of ESI-HRMS as well as one-dimensional (1D) and two-dimensional (2D) spectral NMR datasets. Bioassay results showed that compounds 1–5 displayed anti-inflammatory activity and weak cytotoxicity against cell lines of A549, HT-29, and HepG2.