Stephen W. Ayer

Conditions for the production of jadomycin B by Streptomyces venezuelae ISP5230: effects of heat shock, ethanol treatment and phage infection

SummaryThe novel benzoxazolophenanthridine antibiotic, jadomycin B, is produced byStreptomyces venezuelae ISP5230 following a 42 °C heat shock or exposure to ethanol. To further characterize these unusual culture conditions, studies were carried out using different media, varying nutrient concentrations, initial pH, and time of application of heat or ethanol stress. Highest titers of jadomycin B accumulated 48 h afterS. venezuelae ISP5230 was inoculated into ad-galactose-l-isoleucine production medium (pH 7.5) which was supplemented with ethanol (6%, v/v) between 6 and 13 h. Cultures supplemented with ethanol later than 17 h post inoculation into the production medium produced little or no jadomycin B. Among other heat-shock inducing treatments examined, infection with phage SV1 was associated with increased jadomycin B production. Although jadomycin B titers showed little change with variations in the concentration of phosphate in the production medium, the nature of the nitrogen source was found to be important. Different colored pigments, presumed to be jadomycin B analogs, were formed when other amino acids replacedl-isoleucine in the medium as the sole nitrogen source. Increased jadomycin B titers accompanied increasedl-isoleucine andd-galactose concentrations in the production medium.

Jadomycin, a novel 8H-benz[b]oxazolo[3,2-f]phenanthridine antibiotic from from streptomyces venezuelae ISP5230.☆

In a galactose-isoleucine medium at 37 °C, Streptomyces venezuelae ISP5230 produces jadomycin (1), the first 8H-benz[b]oxazolo[3,2]phenanthridine derivative to be isolated from natural sources. The structure of 1 was assigned by interpretation of the spectral data.

Sulfoquinovosyl diacylglycerols from the alga Heterosigma carterae

An extract of the chloromonad Heterosigma carterae (Raphidophyceae), cultivated in natural seawater, contained a complex mixture of sulfoquinovosyl diacylglycerols. Palmitoyl (16:0), three isomers of hexadecenoyl (16:1 cis Δ9, Δ11, Δ13), and eicosapentenoyl (20:5) were found to be the main fatty acyl substituents. Exact double-bond sites were determined by mass spectrometry analysis of the corresponding nicotinyl derivatives. Four major sulfoquinovosyl diacylglycerol components were partially purified and identified as 1–4 by interpretation of their nuclear magnetic resonance and mass spectral data. In addition, complete analysis of the H. carterae sulfoquinovosyl diacylglycerols was performed using high-performance liquid chromatography combined with electrospray tandem mass spectrometry.

The use of nicotinates and sulfoquinovosyl monoacylglycerols in the analysis of monounsaturated n-3 fatty acids by mass spectrometry.

Fatty acyl groups (16∶1 and 16∶0) liberated from purified sulfoquinovosyl diacylglycerols produced by the unicellular marine microalga,Heterosigma carterae (formerlyH. akashiwo), were converted to either the corresponding alcohols or methyl esters. Nicotinate derivatives of the alcohols were examined by combined gas chromatography/mass spectrometry, and the methyl esters were examined by nuclear magnetic resonance (NMR) spectroscopy after separation by high-performance liquid chromatography. Three different hexadecenoyl fatty acyl groups were identified, one of which wascis 13-hexadecenoyl (16∶1n−3). Both the configuration and the n−3 position of the double bond in thecis 13-hexadecenoyl moiety were unequivocally established by NMR analysis of the corresponding methyl ester. The nicotinate derived from the alcohol of the 16∶1n−3 fatty acyl moiety gave a characteristic fragmentation series in the electron impact msss spectrum which, by careful interpretation, was consistent with, but not unambiguous for, the assigned location of the double bond. Tandem mass spectrometry experiments on a sulfoquinovosyl monoacylglycerol containing thecis 13-hexadecenoyl group in thesn-2 position, using negative-ion liquid secondary ion mass spectrometry, also gave a fragmentation pattern which was consistent with the positional assignment of the double bond.

Microorganisms: A Remarkable Source of Diverse Chemical Structures for Herbicide Discovery

The success of any high throughput chemical screening program is largely dependent upon the quality and structural diversity of the compounds tested. The exceptional biosynthetic capabilities of microorganisms suggest that the search for novel microbial metabolites possessing activity against plant diseases, insects, and weeds could be a particularly valuable addition to a classical synthetic chemical screen.1 This approach has been validated by the commercial introduction of weed control products based upon the streptomycete metabolite phosphinothricylalanylalanine2 and by the introduction of insect control products based upon the streptomycete metabolite avermectin.3