Etude structurale et métabolique des acides mycoliques de Mycobacterium fortuitum

Authors

  • Charlotte LACAVE,

    1. Centre de Recherche de Biochimie et de Génétique Cellulaires du Centre National de la Recherche Scientifique associéà l'Université Paul-Sabatier, Toulouse
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  • Marie-Antoinette LANÉELLE,

    1. Centre de Recherche de Biochimie et de Génétique Cellulaires du Centre National de la Recherche Scientifique associéà l'Université Paul-Sabatier, Toulouse
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  • Mamadou DAFFÉ,

    1. Centre de Recherche de Biochimie et de Génétique Cellulaires du Centre National de la Recherche Scientifique associéà l'Université Paul-Sabatier, Toulouse
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  • Henri MONTROZIER,

    1. Centre de Recherche de Biochimie et de Génétique Cellulaires du Centre National de la Recherche Scientifique associéà l'Université Paul-Sabatier, Toulouse
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  • Marie-Pierre ROLS,

    1. Centre de Recherche de Biochimie et de Génétique Cellulaires du Centre National de la Recherche Scientifique associéà l'Université Paul-Sabatier, Toulouse
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  • Cécile ASSELINEAU

    Corresponding author
    1. Centre de Recherche de Biochimie et de Génétique Cellulaires du Centre National de la Recherche Scientifique associéà l'Université Paul-Sabatier, Toulouse
      Correspondance à C. Asselineau, Centre de Recherche de Biochimie et de Génétique Cellulaires du CNRS associéè l'Université Paul-Sabatier, 118 Route de Narbonne, F-31062 Toulouse Cedex, France
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  • Les auteurs rermercient Monsieur Jean Roussel, et le service de Spectrométrie de Masse du Centre de Recherche de Biochimie et Génétique Cellulaires du Centre National de la Recherche Scientifique, pour la détermination des masses moléculaires des méromycolates et des mycolates. Ce travail a bénéficié d'une subvention de l'Aide è la Recherche Médicale.

Correspondance à C. Asselineau, Centre de Recherche de Biochimie et de Génétique Cellulaires du CNRS associéè l'Université Paul-Sabatier, 118 Route de Narbonne, F-31062 Toulouse Cedex, France

Abstract

Structural and metabolic studies of the mycolic acids of Mycobacterium fortuitum. The biosynthesis of mycolic acids was studied in whole cells of Mycobacterium fortuitum. At first the structures of the main mycolates produced by the used strain were established as diunsaturated and epoxymycolates. By using [1-14C]acetate as a radiotracer of the lipid synthesis, it was observed that the turnover of the mycolates during the exponential phase of growth of M. fortuitum is fast enough to make very difficult the identification of their precursors.

If the growth of the bacterial cells is stopped or highly diminished, by the removal of a large part of their nutritional medium, mycolate synthesis, in contrast to the synthesis of other fatty acids, is stopped as shown by incubation of the concentrated bacterial culture with [1-14C]acetate. After removal of aliquots of the sedimented bacteria at intervals, during several hours, mycolate synthesis resumes when the cell concentration becomes lighter. In these conditions the sequence of radiolabeling of mycolates and of their potential precursors (tetracosanoate and meromycolates) can be observed. In spite of their low accumulation, tetracosanoate and meromycolates were isolated and purified and their specific radioactivity, after different incubation times, could be measured.

The results are in agreement with the hypothesis that meromycolates are condensed with tetracosanoate to produce mycolates. However, because of the large differences of isotopic dilution of these two precursors inside the mycolate molecule, this hypothesis, generally taken as evidence, has to be modified. A hypothetical pathway of the mycolate synthesis is proposed, taking into account all these observations.

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