3-Methylpseudouridine as a fermentation product.

3-Methylpseudouridine (beta isomer) has been identified in fermentation broths of Nocardia lactamdurans. It accumulates at quite high levels following the accumulation of extracellular uracil in strains exhibiting increased levels of de novo pyrimidine biosynthetic enzymes. It is labeled by exogenous uracil, and appears to result from an irreversible modification of one of the components of the elevated pyrimidine pool. Its methyl group is labeled efficiently by [methyl-14C]methionine.

A resting cell system for efrotomycin biosynthesis.

Efrotomycin, a modified polyketide antibiotic with utility as a growth permittant in the animal industry, is produced by Nocardia lactamdurans. A resting cell system has been developed to facilitate biosynthetic studies. Washed cells harvested from oil-based medium at 64 hours and resuspended in buffer produce up to 700 mg/ml efrotomycin in 60 hours when supplemented with a carbon source, optimally glucose. No evidence of carbon or nitrogen repression was observed. Productivity declines progressively with cell age but becomes less dependent on ongoing protein synthesis. The protein synthesis dependent and independent systems were used to study carbon utilization, incorporation of labeled precursors and to examine inhibitors of efrotomycin biosynthesis. A system derived from an efrotomycin non-producer was used to examine the glycosylation of the aglycone, aurodox, to efrotomycin through a monosaccharide form, 6'-deoxyallosyl aurodox.

Studies on antibiotics BN-227 and BN-227-F, new antibiotics. I. Taxonomy, isolation and characterization.

The two new antibiotics, BN-227 and BN-227-F, were isolated from the fermentation broth of Pseudomonas sp. BN-227. BN-227 has a molecular formula C7H9NO3, and melts at 115 degrees C. BN-227-F has a molecular formula C21H24N3O9Fe, and melts at 156 degrees C. BN-227-F is a chelate compound consisting of three similar ligands (antibiotic BN-227) and ferric ion. The two antibiotics have antimicrobial activity against Gram-positive and Gram-negative bacteria.

Use of 13C in biosynthetic studies. The labelling pattern in tenellin enriched from isotope-labelled acetate, methionine, and phenylalanine.

The biogenetic origin of the carbon atoms in tenellin has been established by adding 13C-enriched compounds to cultures of Beauveria bassiana, and determining the isotopic distribution in the metabolite by 13C nuclear magnetic resonance spectrometry. Tenellin is formed by condensation of an acetate-derived polyketide chain with a phenylpropanoid unit that may be phenylalanine. Alternate carbon atoms of the polyketide chain were labelled with sodium [1(-13C)]- and [2-(13C]-acetate; sodium [1,2-(13C)]acetate was incorporated as intact two-carbon units, the presence of which in tenellin was apparent from coupling between adjacent 13C-enriched carbons. Substituent methyl groups of the polyketide-derived alkenyl chain were labelled with L-[Me-13C]methionine. The labelling patterns from DL-[carboxy-13C]phenylalanine and DL-[alpha-13C]phenylalanine indicated a rearrangement of the propanoid component at some stage in the synthesis. The mass spectrum of tenellin from cultures administered L-[15N]phenylalanine showed isotopic enrichment similar to that obtained with 13C- or 14C-labelled phenylalanine. During incorporation of L-[carboxy-14C, beta-3H]phenylalanine 96% of the tritium label was lost, discounting the possibility of a 1,2-hydride shift during biosynthesis of the metabolite.