Metabolism of phytane by Mycobacterium ratisbonense under nitrogen-limiting conditions

SILVA RA,; GROSSI V,; ALVAREZ, H. M.

Orlando, Florida, USA

Congreso; 106th General Meeting of the American Society for Microbiology (ASM); 2006

ASM

Actinomycetes possess wide metabolic capabilities for biodegradation of diverse compounds and are able to accumulate storage lipids, such as triacylglycerols (TAG) and wax esters, from diverse substrates. Here we report on the accumulation of storage lipids by Mycobacterium ratisbonense strain SD4 during growth on 2,6,10,14-tretramethylhexadecane (phytane) under nitrogen-limiting conditions. In some cultures, triclosan (3 ìg/ml) was used as an inhibitor of the de novo fatty acid biosynthesis pathway. Cellular lipids were extracted and then separated by thin layer chromatography. The structural characterization of the storage lipids was done using gas chromatography-mass spectrometry. Strain SD4 was able to produce significant amounts of TAG during cultivation on gluconate and hexadecane, respectively. Surprisingly, during growth on phytane, cells produced wax esters but no TAG. Those lipids consisted in a mixture of isoprenoid wax esters, with 2,6,10,14-tetramethyl-hexadecan-1-ol and 3,7,11,15-tetramethylhexadecan-2-ol as alcohol moieties, and 2,6,10,14-tetramethyl-C16; 3,7,11,15-tetramethyl-C16; 4,8,12-trimethyl-C14; 2,6,10-trimethyl-C12 and 4,8-dimethyl-C10 as acidic moieties. During growth in the presence of triclosan, wax esters containing isoprenoid alcohols esterified to linear fatty acids (C14:0; C15:0, C18:0 and C18:1) were produced, in addition to the aforementioned isoprenoid waxes. Thus, strain SD4 oxidizes phytane both at the isopropyl side of the molecule and at the sub-terminal carbon of the ethyl-terminus. Oxidation of phytane to the isoprenoid acids and subsequent beta-oxidation was also demonstrated. Oxidation products were used for synthesis of waxes, but not TAG. The presence of triclosan in the medium altered the composition of the accumulated lipids. The composition of storage lipids may be controlled precisely according the metabolic background of cells regarding the availability of intermediates.