RESUMEN

The dearth of new antibiotics in the face of widespread antimicrobial resistance makes developing innovative strategies for discovering new antibiotics critical for the future management of infectious disease. Understanding the genetics and evolution of antibiotic producers will help guide the discovery and bioengineering of novel antibiotics. We discovered an isolate in Alaskan boreal forest soil that had broad antimicrobial activity. We elucidated the corresponding antimicrobial natural products and sequenced the genome of this isolate, designated Streptomyces sp. 2AW. This strain illustrates the chemical virtuosity typical of the Streptomyces genus, producing cycloheximide as well as two other biosynthetically unrelated antibiotics, neutramycin, and hygromycin A. Combining bioinformatic and chemical analyses, we identified the gene clusters responsible for antibiotic production. Interestingly, 2AW appears dissimilar from other cycloheximide producers in that the gene encoding the polyketide synthase resides on a separate part of the chromosome from the genes responsible for tailoring cycloheximide-specific modifications. This gene arrangement and our phylogenetic analyses of the gene products suggest that 2AW holds an evolutionarily ancestral lineage of the cycloheximide pathway. Our analyses support the hypothesis that the 2AW glutaramide gene cluster is basal to the lineage wherein cycloheximide production diverged from other glutarimide antibiotics. This study illustrates the power of combining modern biochemical and genomic analyses to gain insight into the evolution of antibiotic-producing microorganisms.

RESUMEN

Endophytes isolated from tropical plants represent a largely untapped reservoir of bioactive secondary metabolites. We screened a library of fungal endophyte extracts for inhibition of the plant pathogen, Pythium ultimum, and purified an active compound using bioassay-guided fractionation. A new nonenolide, (4S,7S,8S,9R)-4-O-succinyl-7,8-dihydroxy-9-heptyl-nonen-9-olide, was isolated and named xyolide. The structure was elucidated by a combination of 1D and 2D NMR methods and the absolute configuration was determined by exciton-coupled circular dichroism. The MIC of xyolide against P. ultimum was 425 µM.

RESUMEN

We report a concise synthesis of A-factor, the prototypical γ-butyrolactone signalling compound of Streptomyces bacteria. In analogy to enzymatic reactions in A-factor biosynthesis, our synthesis features a tandem esterification-Knoevenagel condensation yielding a 2-acyl butenolide and a surprising, chemoselective conjugate reduction of this α,ß-unsaturated carbonyl compound using sodium cyanoborohydride.

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RESUMEN

The pimaricin-inducing (PI) factor, produced by Streptomyces natalensis is a proposed pheromone with a peculiar vicinal diamine structure. The first synthesis of this molecule is reported. It features oxidative dimerization of an aci-nitro anion derived from tris(hydroxymethyl)nitromethane and disproportionation catalyst-facilitated hydrogenation of the resulting vicinal tertiary dinitro compound. As the synthesis requires only four steps with no chromatographic separations, it provides a convenient route to prepare PI factor for biological studies and industrial applications.

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