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PLoS Pathog. 2014 Feb 20;10(2):e1003928. doi: 10.1371/journal.ppat.1003928. eCollection 2014 Feb.

Mycobacterium tuberculosis exploits asparagine to assimilate nitrogen and resist acid stress during infection.

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Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France ; Université de Toulouse, Université Paul Sabatier, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France.
Mycobacterial Research Division, MRC National Institute for Medical Research, London, United Kingdom.
Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Pisa, Italy.
Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America.
Centre d'Immunologie de Marseille-Luminy (CIML), Inserm UMR 1104, CNRS UMR 7280, Aix-Marseille University UM 2, Marseille, France.
Institut Curie, Laboratoire de Microscopie Ionique, Orsay, France ; INSERM U759, Orsay, France.
Institut Pasteur, Unité de Pathogénomique Mycobactérienne Intégrée, Paris, France.


Mycobacterium tuberculosis is an intracellular pathogen. Within macrophages, M. tuberculosis thrives in a specialized membrane-bound vacuole, the phagosome, whose pH is slightly acidic, and where access to nutrients is limited. Understanding how the bacillus extracts and incorporates nutrients from its host may help develop novel strategies to combat tuberculosis. Here we show that M. tuberculosis employs the asparagine transporter AnsP2 and the secreted asparaginase AnsA to assimilate nitrogen and resist acid stress through asparagine hydrolysis and ammonia release. While the role of AnsP2 is partially spared by yet to be identified transporter(s), that of AnsA is crucial in both phagosome acidification arrest and intracellular replication, as an M. tuberculosis mutant lacking this asparaginase is ultimately attenuated in macrophages and in mice. Our study provides yet another example of the intimate link between physiology and virulence in the tubercle bacillus, and identifies a novel pathway to be targeted for therapeutic purposes.

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