Evaluation of the Synthetic Potential of an AHBA Knockout Mutant of the Rifamycin Producer Amycolatopsis mediterranei

Abstract

Supplementing an AHBA(-) mutant strain of Amycolatopsis mediterranei, the rifamycin producer, with a series of benzoic acid derivatives yielded new tetraketides containing different phenyl groups. These mutasynthetic studies revealed unique reductive properties of A. mediterranei towards nitro- and azidoarenes, leading to the corresponding anilines. In selected cases, the yields of mutaproducts (fermentation products isolated after feeding bacteria with chemically prepared analogs of natural building blocks) obtained are in a range (up to 118 mg L(-1)) that renders them useful as chiral building blocks for further synthetic endeavors. The configuration of the stereogenic centers at C6 and C7 was determined to be 6R,7S for one representative tetraketide. Importantly, processing beyond the tetraketide stage is not always blocked when the formation of the bicyclic naphthalene precursor cannot occur. This was proven by formation of a bromo undecaketide, an observation that has implications regarding the evolutionary development of rifamycin biosynthesis.

Natural Products Produced in Culture by Biosynthetically Talented Salinispora arenicola Strains Isolated from Northeastern and South Pacific Marine Sediments

“…The natural product 3 has the same constitution as a compound produced by a mutated rifamycin producer A. mediterranei S699 (-AHBA synthase) that had been fed 3,5-dihydroxybenzoic acid [ 8 ]. Our discovery of 3 in extracts of S. arenicola strain RJA3005 cultures is the first report of 3 as a natural product from a wild-type bacterial culture, and indeed as an entirely biosynthesized molecule.…”

“…A compound isolated from cultures of a rifamycin producer A. mediterranei S699 that was subjected to mutations was assigned the constitution of 4 solely based on HPLC MS data. Two of the A. mediterranei S699 mutations involved the loss of a 21kb DNA fragment [ 8 , 9 ] of the rifamycin gene cluster’s post-PKS modification genes [ 10 ] and a mutation involving a rifF deletion [ 9 ]. The samples of 4 identified from cultures of the mutant strains were never fully characterized by NMR analysis and, to the best of our knowledge, 4 has not been reported as a natural product from cultures of a wild-type bacterium.…”

“…Both 3 and 4 had been previously reported as metabolic products of laboratory mutated and/or engineered rifamycin-producing bacteria, but not as natural products. In particular, 3 was the product of a mutasynthetic study where an -AHBA mutant was fed various synthetically derived starting units [ 8 ]. The structural similarity of both compounds to a mutasynthesized compound (for 3 ) [ 8 ] and an engineered compound (for 4 ) [ 9 ] from a rifamycin producer strongly support that 3 and 4 are the products of the rifamycin gene cluster.…”

“…However, as part of this exercise, we discovered the very minor metabolites salinorcinol ( 3 ) and salinacetamide ( 4 ). Compound 3 has been reported as the product of feeding an engineered Amycolatopsis mediterranei S699 strain (-AHBA synthase) with synthetic aromatic precursors [ 8 ], and compound 4 has been reported as a shunt product of an engineered A. mediterranei S699 strain [ 9 ], but neither 3 nor 4 has been reported as a natural product produced by a wild-type bacteria in culture. Investigation of very minor metabolites with unusual UV spectra in the organic extract of cultures of S. arenicola strain RJA4486 resulted in the isolation of the aminoquinone salinisporamine ( 5 ).…”

Anticancer activity and toxicity of new quaternary ammonium geldanamycin derivative salts and their mixtures with potentiators

“…These analogues showed attractive activities against the cancer cell lines, such as human breast adenocarcinoma (SKBR-3, MCF-7, and MDA-MB-231), ovarian adenocarcinoma (SKOV-3), lung adenocarcinoma (A-549), and prostate adenocarcinoma (PC-3). 2,4,[14][15][16][17][18][19][20] Moreover, modifications at the ansa-macrolide correlated to the preparation of conjugates with biotin, foliate, or within corporated triazole bridge, that gained molecular probe features of improved biocompatibility. [21][22][23][24] Overall, the ansa-bridge modifications of GDM led to a less effective anticancer potency than those performed at the rigid benzene or benzoquinone cores.…”