title: FadD is required for utilization of endogenous fatty acids released from membrane lipids.
abstract: FadD is an acyl coenzyme A (CoA) synthetase responsible for the activation of exogenous long-chain fatty acids (LCFA) into acyl-CoAs. Mutation of fadD in the symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti promotes swarming motility and leads to defects in nodulation of alfalfa plants. In this study, we found that S. meliloti fadD mutants accumulated a mixture of free fatty acids during the stationary phase of growth. The composition of the free fatty acid pool and the results obtained after specific labeling of esterified fatty acids with a Δ5-desaturase (Δ5-Des) were in agreement with membrane phospholipids being the origin of the released fatty acids. Escherichia coli fadD mutants also accumulated free fatty acids released from membrane lipids in the stationary phase. This phenomenon did not occur in a mutant of E. coli with a deficient FadL fatty acid transporter, suggesting that the accumulation of fatty acids in fadD mutants occurs inside the cell. Our results indicate that, besides the activation of exogenous LCFA, in bacteria FadD plays a major role in the activation of endogenous fatty acids released from membrane lipids. Furthermore, expression analysis performed with S. meliloti revealed that a functional FadD is required for the upregulation of genes involved in fatty acid degradation and suggested that in the wild-type strain, the fatty acids released from membrane lipids are degraded by β-oxidation in the stationary phase of growth.
authors.affiliation: Programa de Ecología Genómica, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apdo Postal 565-A, Cuernavaca Morelos C.P. 62210, Mexico.
authors.forename: Ángel
authors.initials: Á
authors.lastname: Pech-Canul
authors.forename: Joaquina
authors.initials: J
authors.lastname: Nogales
authors.forename: Alfonso
authors.initials: A
authors.lastname: Miranda-Molina
authors.forename: Laura
authors.initials: L
authors.lastname: Álvarez
authors.forename: Otto
authors.initials: O
authors.lastname: Geiger
authors.forename: María José
authors.initials: MJ
authors.lastname: Soto
authors.forename: Isabel M
authors.initials: IM
authors.lastname: López-Lara
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D003066:Coenzyme A Ligases / Q000235:genetics / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism*; D008563:Membrane Lipids / Q000378:metabolism*; D009154:Mutation; D016962:Sinorhizobium meliloti / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005227:Fatty Acids; D008563:Membrane Lipids; D003066:Coenzyme A Ligases