Adaptation des mycobactéries à leur environnement (nouvelles approches par spectrométrie de masse)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Metabolite profiling of pea roots in response to phosphate availability

The arbuscular mycorrhizal (AM) symbiosis is a mutualistic association between soil fungi (Glomeromycota) and roots of most plant species. A recent study showed that high phosphate fertilization could inhibit mycorrhizal colonization at a very early stage, before hyphopodium formation. The authors proposed that inhibiting and/or stimulatory compounds might be present in roots grown under high phosphate or low phosphate, respectively. To further address this question, we performed metabolite profiling analyses of extracts of pea roots grown under low and high phosphate concentrations. Ultra high performance liquid chromatography (UHPLC) was coupled with high resolution (HR) mass spectrometry (Q-TOF) and multivariate statistical analysis. This allowed the detection of 34 ions discriminating the two conditions. A majority (28 ions) were more abundant in roots grown under low phosphate concentration, and among them four were specific of this condition. The results suggest that the regulation of AM symbiosis by phosphate may involve the synthesis or accumulation of stimulatory compounds in roots grown under low phosphate

Dynamic comprehension of lipid metabolism : application of 2H2O and Mass Spectrometry to evaluate functional effects of nutrients and implication of nuclear receptors

National audienc

Mycobacterium tuberculosis phoP mutant: lipoarabinomannan molecular structure.

International audienceMycobacterium tuberculosis encodes two-component signal systems. Recently, it was established that the viability of the M. tuberculosis phoP mutant is attenuated in the mouse, suggesting the requirement of the phoP gene for M. tuberculosis intracellular growth. It is now largely acknowledged that M. tuberculosis mannosylated lipoarabinomannans (ManLAM) play a key role in M. tuberculosis intramacrophagic survival by altering the macrophage functions. So ManLAM were extracted and purified from the M. tuberculosis MT103 wild-type strain and from the M. tuberculosis phoP mutant. Their two major functional domains (i) the mannooligosaccharide caps and (ii) the mannosyl phosphatidylinositol anchor were here investigated. Using capillary electrophoresis, it is demonstrated that both mutant and wild-type M. tuberculosis strains share the same capping motifs: mono-, di- and trimannosyl alpha(1-->2) units, with the same relative abundance. Using two-dimensional NMR spectroscopy, the same acyl forms were found to be shared by both strains. However, their relative abundance was quite different. Indeed, in the phoP mutant a decrease of the triacylated ManLAM and an increase of the monoacylated ManLAM were observed. The difference in the proportion of ManLAM acyl forms and the reduced virulence of the M. tuberculosis phoP mutant are discussed