A desA3 knock-out Mycobacterium smegmatis mutant is unable to synthesize palmitoleic acid

DOPRADO MARIANA; CYBULSKI LARISA; RICARDO MORBIDONI

Potrero de los Funes, San Luis

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Bioquímica y Biología Molecular; 2011

Sociedad Argentina de Bioquímica y Biol Mol

Fatty acid desaturases are enzymes that introduce double bonds into saturated fatty acids to yield unsaturated fatty acids (UFAs). In mycobacteria UFAs are essential for growth. Oleic (C18:1) and palmitoleic (C16:1) acids are present in membrane phospholipids, mycolic acids, lypoglycans and triglycerides. Despite the importance of UFAs in the mycobacterial physiology, little is known about the mechanisms of their synthesis and regulation. DesA3 is the only stearoyl-desaturase from Mycobacterium tuberculosis, whereas at least five homologous genes are encoded in the genome of M. smegmatis (MSMEG_1886, MSMEG_1211, MSMEG_1743, MSMEG_6835 and MSMEG_3333). We generated knock-out mutants of MSMEG_1886 and MSMEG_1211 on the basis of their high homology to DesA3: we evaluated the growth of M.smegmatis D1886 in liquid and solid media and the lipid profile by TLC and GC/MS in presence/absence of oleic acid at 25, 37 and 42°C. The mutant grown in the absence of oleic acid displayed an altered colony morphology and could grow (albeit at slower rate) at 37 and 42°C, but was unable to grow at 25°C. Fatty acid analysis revealed that C18:1 was severely reduced and C16:1 was absent. These data suggest that MSMEG_1886 could be a fatty acid desaturase, with specificity for palmitic acid.