Different Biosynthetic Pathways to Fosfomycin in Pseudomonas syringae and Streptomyces Species

Abstract

ABSTRACTFosfomycin is a wide-spectrum antibiotic that is used clinically to treat acute cystitis in the United States. The compound is produced by several strains of streptomycetes and pseudomonads. We sequenced the biosynthetic gene cluster responsible for fosfomycin production inPseudomonas syringaePB-5123. Surprisingly, the biosynthetic pathway in this organism is very different from that inStreptomyces fradiaeandStreptomyces wedmorensis. The pathways share the first and last steps, involving conversion of phosphoenolpyruvate to phosphonopyruvate (PnPy) and 2-hydroxypropylphosphonate (2-HPP) to fosfomycin, respectively, but the enzymes converting PnPy to 2-HPP are different. The genome ofP. syringaePB-5123 lacks a gene encoding the PnPy decarboxylase found in theStreptomycesstrains. Instead, it contains a gene coding for a citrate synthase-like enzyme, Psf2, homologous to the proteins that add an acetyl group to PnPy in the biosynthesis of FR-900098 and phosphinothricin. Heterologous expression and purification of Psf2 followed by activity assays confirmed the proposed activity of Psf2. Furthermore, heterologous production of fosfomycin inPseudomonas aeruginosafrom a fosmid encoding the fosfomycin biosynthetic cluster fromP. syringaePB-5123 confirmed that the gene cluster is functional. Therefore, two different pathways have evolved to produce this highly potent antimicrobial agent.