Tailed bacteriophages: the order caudovirales

Area of Science:

• Virology
• Molecular Biology
• Evolutionary Biology

Background:

• Tailed bacteriophages, order Caudovirales, possess unique structured tails and exhibit diverse facultative viral features.
• Their evolutionary history, including morphogenesis and lifestyle, shows parallels with herpesviruses, suggesting convergent evolution.
• Lysogeny in tailed phages, exemplified by lambda, Mu, and P1, appears to be a secondary acquisition via horizontal gene transfer.

Purpose of the Study:

• To reconstruct the evolutionary history of tailed bacteriophages.
• To identify key ancestral traits and diversification events in Caudovirales.
• To understand the role of horizontal gene transfer in shaping tailed phage genomes and lifestyles.

Main Methods:

• Analysis of amino acid sequences of key viral proteins (DNA polymerases, integrases, peptidoglycan hydrolases) to infer horizontal gene transfer events.
• Comparative analysis of genomic structure, capsid, and tail protein evolution.
• Reconstruction of ancestral phage characteristics based on conserved features.

Main Results:

• Tailed phages likely originated from a simple precursor virus in the early Precambrian.
• The ancestral tailed phage possessed an icosahedral head, a long non-contractile tail, dsDNA genome, and lacked lipids.
• Diversification involved evolution of tail structures, gene acquisition through horizontal transfer, and acquisition of lysogeny.
• Modern tailed phages are chimeric but retain evidence of monophyletic origin in morphology and replication strategies.

Conclusions:

• Tailed phages exhibit a monophyletic origin despite extensive genetic exchange and diversification.
• Their unique morphology and replication strategies are hallmarks of their ancient lineage.
• Horizontal gene transfer has played a significant role in their adaptation and evolution, leading to their current diversity.