Toxin–antitoxin vapBC locus participates in formation of the dormant state in Mycobacterium smegmatis

Authors

  • Oksana I. Demidenok,

    Corresponding author
    1. Laboratory of Biochemistry of Stresses in Microorganisms, A.N. Bach Institute of Biochemistry Russian Academy of Sciences, Moscow, Russia
    • Correspondence: Oksana I. Demidenok, Laboratory of Biochemistry of Stresses in Microorganisms, A.N. Bach Institute of Biochemistry Russian Academy of Sciences, Leninsky prospekt 33, build. 2, 119071 Moscow, Russia. Tel.: +7 495 954 40 47; fax: +7 495 954 27 32;

      e-mail: demidenoksana@gmail.com

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  • Arseny S. Kaprelyants,

    1. Laboratory of Biochemistry of Stresses in Microorganisms, A.N. Bach Institute of Biochemistry Russian Academy of Sciences, Moscow, Russia
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  • Anna V. Goncharenko

    1. Laboratory of Biochemistry of Stresses in Microorganisms, A.N. Bach Institute of Biochemistry Russian Academy of Sciences, Moscow, Russia
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Abstract

Toxin–antitoxin (TA) loci are widely spread in bacterial plasmids and chromosomes. Toxins affect important functions of bacterial cells such as translation, replication and cell-wall synthesis, whereas antitoxins are toxin inhibitors. Participation in formation of the dormant state in bacteria is suggested to be a possible function of toxins. Here we show that overexpression of VapC toxin in Mycobacterium smegmatis results in development of morphologically distinct ovoid cells. The ovoid cells were nonreplicating and revealed a low level of uracil incorporation and respiration that indicated their dormant status. To validate the role of VapBC in dormancy formation, we used a model of dormant, ‘nonculturable' (NC) M. smegmatis cells obtained in potassium-limited conditions. Overexpression of VapB antitoxin prevented transition to dormancy, presumably due to a decreased level of the free VapC protein. Indeed, this effect of the VapB was neutralized by coexpression of the cognate VapC as a part of the vapBC operon. In summary, these findings reveal participation of vapBC products in formation of the dormant state in M. smegmatis.

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