Soil bacteria expand antibiotic arsenal

Screening of natural product extracts has unearthed a new antibiotic that could help in the fight against drug-resistant bacteria. Jun Wang, Sheo B. Singh, and colleagues at Merck discovered the antibiotic, which they named platencin (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0700746104). The compound is produced by a strain of Streptomyces platensis that was found in a soil sample collected in Spain. Platencin (shown) resembles the antibiotic platensimycin, which is produced by a different strain of S. platensis that was found in a South African soil sample. The Merck team discovered platensimycin last year by screening a library of 250,000 natural product extracts (C&EN, May 22, 2006, page 7). Both compounds work by striking at the fatty acid synthesis pathway in bacteria. The new antibiotic inhibits two enzymes in that pathway, whereas platensimycin targets just one enzyme. The Merck researchers report that platencin combats a broad range of bacteria, including drug-resistant strains of Staphylococcus aureus. It also has shown potent efficacy in mice without any observed toxicity.