Metabolic profile of Mycobacterium smegmatis revealed that Mce4 proteins are relevant for the lipid homeostasis

SANTANGELO, MARÍA DE LA PAZ; HEUBERGER, A; KLEPP, LAURA INÉS; BLANCO, FEDERICO CARLOS; FORRELLAD, MARINA ANDREA; NIQUEL, PABLO; JACKSON, MARY; BIGI, FABIANA

Canela, RS

Congreso; VII Meeting of the SLAMTB; 2014

Sociedad Latinoamericana de Tuberculosis y otras Micobacteriosis

Objectives: The Mce proteins are a group of secreted or cell wall proteins encoded in large operons with identical structure in all Mycobacterium species examined. Although the function of the Mce protein family has not been clearly established, it has been hypothesized that they are membrane transporters of lipid. In order to get some insights in this question, we analyzed the impact of the deletion of the Mce proteins in the metabolism of Mycobacterium smegmatis. Methods: Metabolic profile of two mutants lacking the mce4 or the six mce operons of M. smegmatis was performed GC-MC. qRT-PCR and lipid analysis by TLC were used to validate GC-MS results. Results: Metabolomic data were overviewed with a Principal Component Analysis. PC1 separated WT from the mutants, explaining 77,28% of the variation due to de biotype, while the media (PC2) only explained 7,89% of the variation. These results indicate that the deletion of the mce4 operon, the first one deleted in the series, resulted in a unique metabolite profile differing from the WT. We then evaluated transcript variation using qRT-PCR of the main enzymes involved in the metabolic pathways where we found differences. Finally, we performed total lipid analysis by TLC. We found an accumulation of TAG in the mutant strains compared to the WT. Conclusions: The lack of the mce4 operon in M. smegmatis is consistent with an accumulation of the storage lipid TAG in response to stress in vitro, concurrent with decreased fatty acid incorporation into phospholipids and loss of acid-fastness.