AEROBIC PATHWAY FOR UNSATURATED FATTY ACID SYNTHESIS IN PEANUT NODULATING RHIZOBIA

PAULUCCI N; MEDEOT D; WOELKE M; DARDANELLI M; GARCÍA M DE LEMA

San Luis

Congreso; SAIB; 2011

SAIB

In Bradyrhizobium sp.TAL1000 and Ensinfer meliloti 1021, unsaturated fatty acids (UFA) play an important role in maintaining the fluidity of the membrane against a change in environmental conditions. In certain bacteria the synthesis of UFA occurs by an aerobic mechanism, mediated by desaturase enzymes (Shanklin et al., 1998). In the present work, we have succeeded in cloning a gene encoding a putative desaturase from B. TAL1000 and E. meliloti 1021 and have determined its function by expression in E. coli. The putative desaturase genes from B. TAL1000 and E. meliloti 1021 were amplified by PCR and cloned into plasmid pET17b. These construct were used to transform E. coli. After addition of IPTG, the cultures of transformed E. coli strains were collected and their FA compositions were analyzed by GC. Desaturase activity was analyzed by addition of radioactive FA to the culture. The levels of 16:0 and 18:0 decreased, while 16:1 Δ9 and 18:1 (Δ11+Δ9) levels were enhanced in both transformed strains compared to the control. E.coli strains overexpressing each of the putative desaturase genes were able to desaturate [1-14C] 16:0 and [1-14C] 18:0 to monounsaturated FA. These results indicate that Bradyrhizobium sp.TAL1000 and Ensinfer meliloti 1021 contain in their genomes a gene of a single sequence encoding a FA desaturase.