Malic enzyme is involved in triacylglycerol metabolism in Rhodococcus.

HERNANDEZ MA; ROST E; ALVAREZ, H. M.

Tucumán

Congreso; VII Congreso Argentino de Microbiologia General (SAMIGE); 2011

Sociedad Argentina de Microbiología General (SAMIGE)

Rhodococcus bacteria, which belong to the non-sporulating and mycolic acid-containing actinomycetes, are able to accumulate variable amounts of triacylglycerols (TAG) as main storage lipids. In a previous transcriptome study, the ro11316 gene was significantly up-regulated during cultivation of Rhodococcus jostii RHA1cells with benzoate under nitrogen-limiting conditions. This condition promotes triacylglycerols (TAG) accumulation by cells of Rhodococcus members. The ro11316 gene, which occurs in the megaplasmid pRHL3 of R. jostii RHA1, codes for a putative malic enzyme. This enzyme may contribute with the NADPH pool generation necessary for TAG biosynthesis in Rhodococcus members. In order to confirm this hypothesis, we analyzed in the model oleaginous bacterium Rhodococus opacus PD630 the in vivo effect of different concentrations (0, 1.5, 5 and 10 mM) of sesamol, an inhibitor of malic enzyme activity. TLC and GC analyses of cells cultivated in N-limiting mineral media (MSM0.1) with gluconate as sole carbon source showed a proportional decrease in TAG cellular content in the presence of different inhibitor concentrations (60, 42.8, 33.4 and 15.0 % w/w of TAG, respectively). No changes in fatty acid profiles of TAG were observed after cultivation of cells with sesamol. In the other hand, the ro11316 gene of R. jostii RHA1 was cloned and expressed under a strong acetamidase promoter in R. opacus PD630. An increase of approximately 15% (w/w) of TAG content was observed in recombinant cells in comparison with wild type cells during cultivation in MSM0.1 with glucose as sole carbon source. The biomass production by recombinant cells was also increased. The results suggested that the product of ro011316 gene and probably their orthologs may be involved in NADPH generation for the de novo fatty acid and TAG biosynthesis in Rhodococcus members.