Siphoviridae

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Siphoviridae
Kingdom:	Caudoviricetes
Phylum:
Class:
Order:
Family:	'Siphoviridae'

Siphoviridae is a family of bacteriophages, which are viruses that infect bacteria. This family is characterized by its long, non-contractile tails and icosahedral heads. Siphoviridae is one of the most diverse and abundant families of bacteriophages, playing a significant role in bacterial ecology and evolution.

Structure

Siphoviridae phages have a distinctive morphology. They possess an icosahedral head, typically about 60 nm in diameter, which contains the viral genome. The genome is usually double-stranded DNA, ranging from 40 to 60 kilobase pairs in length. The tail is long and flexible, measuring approximately 100 to 200 nm, and is non-contractile, distinguishing them from other bacteriophage families such as Myoviridae.

Life Cycle

The life cycle of Siphoviridae phages involves several key stages:

• Attachment: The phage attaches to the bacterial cell surface using its tail fibers, which recognize specific receptors on the host cell.
• Penetration: The phage injects its DNA into the host cell through the tail tube.
• Replication: The phage DNA is replicated using the host's cellular machinery. This process can follow either a lytic or lysogenic cycle.
• Assembly: New phage particles are assembled within the host cell.
• Release: In the lytic cycle, the host cell is lysed, releasing new phage particles to infect other cells. In the lysogenic cycle, the phage DNA integrates into the host genome and replicates along with it until conditions favor the lytic cycle.

Ecological Role

Siphoviridae phages are ubiquitous in nature and play a crucial role in regulating bacterial populations in various environments, including soil, water, and the human gut. They contribute to horizontal gene transfer among bacteria, influencing bacterial evolution and diversity.

Applications

Siphoviridae phages have potential applications in phage therapy, which involves using bacteriophages to treat bacterial infections, especially those resistant to antibiotics. They are also used in molecular biology as tools for genetic engineering and cloning.

Also see

• Bacteriophage
• Myoviridae
• Podoviridae
• Phage therapy
• Viral replication