Identification of a developmental chemoattractant in Myxococcus xanthus through metabolic engineering

Fruiting body formation of Myxococcus xanthus requires the ordered migratio n of tens of thousands of cells by using a form of surface motility known a s gliding and chemical signal(s) that have yet to be elucidated. Directed m ovement is regulated by phosphatidyl ethanolamine (PE) purified from M. xan thus cell membranes. Because the purified PE preparation contains a remarka bly diverse mixture of fatty acids, metabolic engineering was used to eluci date the biologically active fatty acid component. The mutational block in an esg mutant, which renders it defective in producing primers for branched -chain fatty acid biosynthesis, was bypassed with one of a series of primer s that enriches for a particular family of branched-chain fatty acids. Each PE enrichment was observed for chemotactic activity by using an excitation assay and for fatty acid content. The excitation activity of a PE preparat ion was generally proportional with the concentration of the fatty acid 16: 1 omega 5c. 1,2-O-Bis[11-(Z)-hexadecenoyl]-sn-glycero-3-phosphoethanolamine (PE-16:1 omega 5c/16:1 omega 5c) was synthesized and elicited an excitatio n peak at 2 ng. This peak activity occurred at a 1,000-fold lower concentra tion than dilauroyl PE (PE-12:0/12:0) and the peak magnitude was 2-fold hig her. PE containing 16:1 omega 5c is likely to play a role in development be cause it is active at physiological concentrations and only under developme ntal conditions.