Abstract
Aromatic polyketides from marine actinomycetes have received increasing attention due to their unusual structures and potent bioactivities. Compared to their terrestrial counterparts, marine aromatic polyketides have been less discovered and their structural and biological diversities are far from being fully investigated. In this study, we employed a PCR-based genome mining method to discover aromatic polyketides in our marine bacteria collection. Five new atypical angucyclinones, fluostatins M–Q (1–5) featuring a unique 6-5-6-6 ring skeleton, were discovered from one “positive” Streptomyces sp. PKU-MA00045. The structures of fluostatins M–Q (1–5) were elucidated based on comprehensive spectroscopic analyses and the crystallographic structure of fluostatin P (4), which contains the most oxidized A-ring, was solved by X-ray diffraction analysis with Cu Kα radiation. Compared to the published 16 fluostatin analogues, fluostatins M–Q (1–5) contained a different methoxy group attached at C-7 and hydroxy group attached at C-4, enriching the structural diversity of aromatic polyketides from marine actinomycetes. Genome sequencing of Streptomyces sp. PKU-MA00045 revealed the biosynthetic gene cluster of fluostatins M–Q (1–5), which contained different genes and gene organizations compared to known fluostatin gene clusters, facilitating the investigation of the biosynthesis of the unique 6-5-6-6 ring skeleton in all fluostatins.
Highlights
Marine actinomycetes distributed in various habitats including sea deposits, sponges, corals, molluscs, seagrasses and mangroves are emerging as important producers of structurally complex and bioactive natural products [1,2,3,4]
We have constructed a marine bacteria library containing strains isolated from sponges, corals
DNAs offrom strains the library as the templates, using the degenerate primers designed from the conserved sequences of we carried out a PCR screening targeting type II PKSs with genomic DNAs of strains in the library as the templates, using the degenerate primers designed from the conserved sequences of KSα s and
Summary
Marine actinomycetes distributed in various habitats including sea deposits, sponges, corals, molluscs, seagrasses and mangroves are emerging as important producers of structurally complex and bioactive natural products [1,2,3,4]. Since the first marine actinomycete, Rhodococcus marinonascens, was taxonomically described [5], new genera and species of marine actinomycetes have been extensively isolated and identified [2,6,7]. The new genus Salinispora, which is the first marine actinomycete characterized by seawater or sea salts-obligate, has become a model organism for natural products discovery [4]. Varied families of natural products from marine actinomycetes with diverse bioactivities have been recently reviewed [2,3,4,8]. In the natural products produced by marine actinomycetes, aromatic polyketides have received increasing attention especially in the.
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