IBR   13079
INSTITUTO DE BIOLOGIA MOLECULAR Y CELULAR DE ROSARIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Regulation of unsaturated fatty acids in Mycobacterium
Autor/es:
DOPRADO MARIANA; RICARDO MORBIDONI; LARISA CYBULSKI
Lugar:
San miguel de Tucuman
Reunión:
Congreso; VII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL SAMIGE DEL BICENTENARIO; 2011
Institución organizadora:
Sociedad Argentina de Microbiología General
Resumen:
Unsaturated fatty
acids (UFAS) are present in membrane phospholipids, mycolic acids, lypoglycans
and triglycerides of Mycobacteria. Double bonds are also substrate of
cyclopropane, metoxy and ketoacids synthesis, which are all present in mycolic
acids. Despite the relevance that double bonds have in Mycobacteria physiology,
biosynthetic pathways and regulatory mechanisms controlling desaturase
expression are extremely scarce.
Here we employed
thin-layer chromatography and gas chromatography-mass sprectrometry to compare
levels of UFAs of M. smegmatis
grown at different temperatures. We found that palmitoleic and oleic acids
increase at low temperatures. M.
smegmatis genome holds at least 7 desaturases. We selected three genes
homologous to desA1, desA2 and desA3 genes of M. tuberculosis to perform regulatory
tests. Promoters corresponding to desA1(5777),
desA2 (3333) and desA3(9999) genes were cloned
upstream of the beta- galactosidase reporter gene.
Transcription of these genes seems not to increase with lowering temperatures.
To confirm this finding Northern blots were performed. Both results suggest
that either other enzyme is involved in UFA increase at low temperature or that
UFA increase is due to a post-transcriptional control of desaturase activity.
Accordingly, when the desA3-1211 promoter was cloned and analyzed it showed a
temperature-sensitive expression profile. We also analyzed if desA3-1886 transcription was
regulated by end-product by adding oleic acid to the growth medium. We found
that expression of this gene was repressed upon oleic acid addition.
Strikingly, an inverted repeat was located upstream of the desA3-1886 gene, as well as upstream
of the oxido-reductase 1885 gene, and this pattern is conserved in M. tuberculosis. We are now studying
the role of these putative regulatory sequences.