Fatty acids desaturase in Bradyrhizobium peanut nodulant

PAULUCCI, NS; MEDEOT, D.B.; DARDANELLI, MS; BUENO, MA; GARCÍA, MB

Congreso; XLIV Reunión Anual SAIB; 2008

Desaturases (Des) of fatty acids (FA) have been described in eukaryotic as well as procariotic organisms. These introduce double bounds in fatty acids of the membrane phospholipids; their activity is regulated so that the fluidity of the bilayer stays constant, mainly when some changes on the environment happen. In this work we identified a possible desaturase gene in a nodulant peanut rizobio strain and verified the presence ?in vivo?, of a desaturation system of stearic acid (18:0).DNA from Bradyrhizobium TAL 1000 and Ensinfer meliloti (control strain) were extracted and submitted to PCR amplification employing primers of gene des sequence from E. meliloti. The PCR product was sequenced. The enzymatic activity was measured in B. TAL 1000 using 18:0[1-14C] as substrate after 24 h of growth at 28ºC. Lipids were extracted and fatty acids methyl esters were obtained and separated by AgNO3-TLC.A fragment of 1 kb, having a high identity with predicted des gene of E. meliloti and related bacteria, was amplified by PCR. When Des activity was measured, 35% of the radioactivity from stearic acid was recovered in monounsaturated FA fraction. The above results are indicative that B. TAL 1000 would own a desaturation system to generate monounsaturated FA, which would be complementary of the anaerobic system of unsaturated FA formation.