Biological production of 5-methylthioribose

Abstract

Production of methylthioribose by Escherichia coli was investigated under various growth conditions using sulfate as the exogenous source of sulfur. Methylthioribose was shown by tracer and chromatographic methods to be a normal biosynthetic product secreted into the medium and accumulated there. Production of [35S]-methylthioribose decreased by dilution of the radioactivity as total inorganic sulfate increased in a dense suspension of cells preincubated in sulfate-limiting medium. Variations in initial inoculum size had little effect on yield of this product.Formation of methylthioribose increased with decreasing levels of nitrogen under a sulfur deficiency, with decreasing levels of sulfur under a nitrogen deficiency, and with decreasing levels of phosphorus under a combined deficiency of sulfur and nitrogen. Methylthioribose increased in the alcohol-soluble, sulfur-containing fraction on prolonged incubation in phosphate-deficient, sulfate-deficient, and phosphate–sulfate deficient media. In the last two systems methylthioribose made up nearly 100% of the total fraction.In a survey of microorganisms using sulfate as the major source of sulfur, Escherichia coli produced methylthioribose to the greatest extent. Aerobacter aerogenes, Clostridium pasteurianum, and Saccharomyces cerevisiae produced only 2–3% as much. Bacillus subtilis, Staphylococcus aureus, Lactobacillus acidophilus, and Pseudomonas aeruginosa did not form detectable amounts of methylthioribose under conditions of this study.