title: A conditional mutant of the fatty acid synthase unveils unexpected cross talks in mycobacterial lipid metabolism.
abstract: Unlike most bacteria, mycobacteria rely on the multi-domain enzyme eukaryote-like fatty acid synthase I (FAS I) to make fatty acids de novo. These metabolites are precursors of the biosynthesis of most of the lipids present both in the complex mycobacteria cell wall and in the storage lipids inside the cell. In order to study the role of the type I FAS system inMycobacteriumlipid metabolismin vivo, we constructed a conditional mutant in thefas-acpSoperon ofMycobacterium smegmatisand analysed in detail the impact of reduced de novo fatty acid biosynthesis on the global architecture of the cell envelope. As expected, the mutant exhibited growth defect in the non-permissive condition that correlated well with the lower expression offas-acpSand the concomitant reduction of FAS I, confirming that FAS I is essential for survival. The reduction observed in FAS I provoked an accumulation of its substrates, acetyl-CoA and malonyl-CoA, and a strong reduction of C12to C18acyl-CoAs, but not of long-chain acyl-CoAs (C19to C24). The most intriguing result was the ability of the mutant to keep synthesizing mycolic acids when fatty acid biosynthesis was impaired. A detailed comparative lipidomic analysis showed that although reduced FAS I levels had a strong impact on fatty acid and phospholipid biosynthesis, mycolic acids were still being synthesized in the mutant, although with a different relative species distribution. However, when triacylglycerol degradation was inhibited, mycolic acid biosynthesis was significantly reduced, suggesting that storage lipids could be an intracellular reservoir of fatty acids for the biosynthesis of complex lipids in mycobacteria. Understanding the interaction between FAS I and the metabolic pathways that rely on FAS I products is a key step to better understand how lipid homeostasis is regulated in this microorganism and how this regulation could play a role during infection in pathogenic mycobacteria.
authors.affiliation: Laboratory of Physiology and Genetics of Actinomycetes, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.
authors.forename: Matías
authors.initials: M
authors.lastname: Cabruja
authors.affiliation: Laboratory of Physiology and Genetics of Actinomycetes, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.
authors.forename: Sonia
authors.initials: S
authors.lastname: Mondino
authors.affiliation: Laboratory of Physiology and Genetics of Actinomycetes, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.
authors.forename: Yi Ting
authors.initials: YT
authors.lastname: Tsai
authors.affiliation: Laboratory of Physiology and Genetics of Actinomycetes, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.
authors.forename: Julia
authors.initials: J
authors.lastname: Lara
authors.affiliation: Laboratory of Physiology and Genetics of Actinomycetes, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina gramajo@ibr-conicet.gov.ar.
authors.forename: Hugo
authors.initials: H
authors.lastname: Gramajo
authors.affiliation: Laboratory of Physiology and Genetics of Actinomycetes, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina gago@ibr-conicet.gov.ar.
authors.forename: Gabriela
authors.identifier: 0000-0001-7668-0119
authors.initials: G
authors.lastname: Gago
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D064429:Fatty Acid Synthases / Q000235:genetics* / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis; D015964:Gene Expression Regulation, Bacterial; D050356:Lipid Metabolism; D009154:Mutation; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000254:growth & development*; D009876:Operon
chemical_list: D001426:Bacterial Proteins; D005227:Fatty Acids; D064429:Fatty Acid Synthases
keywords: fatty acid synthase I; mycolic acids; tuberculosis