The episodic evolution of fibritin: traces of ancient global environmental alterations may remain in the genomes of T4-like phages

Authors

  • A. V. Letarov,

    Corresponding author
    1. Laboratoire de Microbiologie et Génétique Moléculaires, Centre National de la Recherche Scientifique UMR 5100 Université Paul Sabatier-Toulouse III, Toulouse, Cedex 09, France
    2. Moscow Institute of Physics and Technology State University, Moscow Region, Russia
    • Winogradsky Institute of Microbiology Russian Academy of Science, Moscow, Russia
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  • H. M. Krisch

    1. Laboratoire de Microbiologie et Génétique Moléculaires, Centre National de la Recherche Scientifique UMR 5100 Université Paul Sabatier-Toulouse III, Toulouse, Cedex 09, France
    Current affiliation:
    1. Avenue Général Guisan 38, Sierre (VS), Switzerland
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Correspondence

A. V. Letarov, Winogradsky Institute of Microbiology Russian Academy of Science, 117312, pr. 60-letiya Oktyabrya 7, building 2, Moscow, Russia. Tel: +7-499-135-72-64; Fax: +7-499-135-65-31; E-mail: Letarov@gmail.com

Abstract

The evolutionary adaptation of bacteriophages to their environment is achieved by alterations of their genomes involving a combination of both point mutations and lateral gene transfer. A phylogenetic analysis of a large set of collar fiber protein (fibritin) loci from diverse T4-like phages indicates that nearly all the modular swapping involving the C-terminal domain of this gene occurred in the distant past and has since ceased. In phage T4, this fibritin domain encodes the sequence that mediates both the attachment of the long tail fibers to the virion and also controls, in an environmentally sensitive way, the phage's ability to infect its host bacteria. Subsequent to its distant period of modular exchange, the evolution of fibritin has proceeded primarily by the slow vertical divergence mechanism. We suggest that ancient and sudden changes in the environment forced the T4-like phages to alter fibritin's mode of action or function. The genome's response to such episodes of rapid environmental change could presumably only be achieved quickly enough by employing the modular evolution mechanism. A phylogenetic analysis of the fibritin locus reveals the possible traces of such events within the T4 superfamily's genomes.

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