The crucial role of trehalose and structurally related oligosaccharides in the biosynthesis and transfer of mycolic acids in Corynebacterineae.
Trehalose (alpha-D-glucopyranosyl-alpha'-D-glucopyranoside) is essential for the growth of the human pathogen Mycobacterium tuberculosis but not for the viability of the phylogenetically related corynebacteria. To determine the role of trehalose in the physiology of these bacteria, the so-called Corynebacterineae, mutant strains of Corynebacterium glutamicum unable to synthesize trehalose due to the knock-out of the genes of the three pathways of trehalose biosynthesis, were biochemically analyzed. We demonstrated that the synthesis of trehalose under standard conditions is a prerequisite for the production of mycolates, major and structurally important constituents of the cell envelope of Corynebacterineae. Consistently, the trehalose-less cells also lack the cell wall fracture plane that typifies mycolate-containing bacteria. Importantly, however, the mutants were able to synthesize mycolates when grown on glucose, maltose, and maltotriose but not on other carbon sources known to be used for the production of internal glucose phosphate such as fructose, acetate, and pyruvate. The mycoloyl residues synthesized by the mutants grown on alpha-D-glucopyranosyl-containing oligosaccharides were transferred both onto the cell wall and free sugar acceptors. A combination of chemical analytical approaches showed that the newly synthesized glycolipids consisted of 1 mol of mycolate located on carbon 6 of the non reducing glucopyranosyl unit. Additionally, experiments with radioactively labeled trehalose showed that the transfer of mycoloyl residues onto sugars occurs outside the plasma membrane. Finally, and in contradiction to published data, we demonstrated that trehalose 6-phosphate has no impact on mycolate synthesis in vivo.
Tropis
Marielle
M
Department of Molecular Mechanisms of Mycobacterial Infections, Institut de Pharmacologie et Biologie Structurale (UMR 5089 du CNRS et de l'Université Paul Sabatier) 205, route de Narbonne, 31077 Toulouse cedex 04, France.
Meniche
Xavier
X
Wolf
Andreas
A
Gebhardt
Henrike
H
Strelkov
Sergey
S
Chami
Mohamed
M
Schomburg
Dietmar
D
Krämer
Reinhard
R
Morbach
Susanne
S
Daffé
Mamadou
M
D001622:Betaine / Q000737:chemistry; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism; D002474:Cell-Free System / Q000378:metabolism; D002855:Chromatography, Thin Layer; D003001:Cloning, Molecular; D048230:Corynebacterium glutamicum / Q000378:metabolism*; D003470:Culture Media / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005614:Freeze Fracturing; D005947:Glucose / Q000378:metabolism; D006017:Glycolipids / Q000737:chemistry; D008055:Lipids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008854:Microscopy, Electron; D008954:Models, Biological; D008956:Models, Chemical; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000378:metabolism; D009171:Mycolic Acids / Q000737:chemistry*; D009844:Oligosaccharides / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013403:Sugar Phosphates / Q000737:chemistry; D014199:Trehalose / Q000031:analogs & derivatives / Q000737:chemistry / Q000502:physiology*
D003470:Culture Media; D005227:Fatty Acids; D006017:Glycolipids; D008055:Lipids; D009171:Mycolic Acids; D009844:Oligosaccharides; D013403:Sugar Phosphates; C013898:corynomycolic acid; D001622:Betaine; C082722:trehalose-6-phosphate; D014199:Trehalose; D005947:Glucose