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Bacteriophages: Structure

  1. Ana Cuervo,
  2. José L Carrascosa

Published Online: 15 JUN 2012

DOI: 10.1002/9780470015902.a0024053



How to Cite

Cuervo, A. and Carrascosa, J. L. 2012. Bacteriophages: Structure. eLS. .

Author Information

  1. Centro Nacional de Biotecnología (CNB-CSIC). Darwin 3. Campus de Cantoblanco, Madrid, Spain

Publication History

  1. Published Online: 15 JUN 2012


Bacterial viruses, or bacteriophages, are ubiquitous organisms spanning very different ecological niches. Although genome comparison fails to show extensive relationship among bacteriophages, recent structural studies reveal a high degree of similarities. Most bacteriophages present an icosahedral proteinaceous head, which contains the nucleic acid, either deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). Exceptions to this rule are few cases where a lipid envelope forms part of the head, and those other cases where the head presents a filamentous geometry. The way bacteriophages infect the host cell is the basis of a main difference among them: one group (Caudovirales) has a specialised structure (the tail) that is responsible for the recognition of the host cell and the viral genome delivery, whereas those bacteriophages without tail present a variety of infecting strategies. In this study we will deal with the main common characteristics of bacteriophage heads and tails supporting their common evolutionary origin.

Key Concepts:

  • Bacteriophages share extended structural and functional similarities.

  • Bacteriophages are excellent examples of optimisation of genetic information to carry out complex functions.

  • Most bacteriophages enclose their nucleic acid in a protein container (built by multiple copies of one (or a few) proteins), and in a few cases they may include lipid envelopes.

  • The most conserved geometry in bacteriophage heads is icosahedral.

  • Double stranded DNA icosahedral bacteriophages follow a common assembly pathway.

  • The Caudovirales group (bacteriophages with icosahedral heads, dsDNA and a tail) are the most abundant virus type.

  • The packaging of dsDNA inside Caudovirales requires energy conversion (ATP hydrolysis) into mechanical translocation, and it is carried out by a dedicated viral machinery.

  • The maturation of icosahedral proheads into viral heads involves drastic reorganisations of the capsid components leading to more stable particles.

  • The tail of Caudovirales is a sophisticated machinery involved in cell recognition and nucleic acids delivery.

  • There are three main architectural designs of bacteriophage tails, each one adapting to different host interaction strategies.


  • bacteriophage;
  • structure;
  • phage assembly;
  • bacterial virus;
  • maturation