Podo-type tailed virion

The short tail of podo-type virions acts as a molecular machine that ejects the viral DNA from the capsid into the host cell cytoplasm.

The ejection system consists of a central tube, the connector which attaches the tail to the phage capsid and released inner core proteins.

Upon binding to the host cell surface, podoviruses display a tube-like extension of their short tail that penetrates both host membranes. This tail extension comes from the release of viral core proteins with channel forming properties .

The source of the forces that drive viral genome ejection is probably in part due to osmotic pressure imbalance between the virus inside and the host cytoplasm .

Gram(-) hosts:

1. Attachment to a host cell outer membrane (OM) receptor.
2. Ejection proteins in the head form a channel that penetrates the OM. Virion-associated exolysin (if present) hydrolyzes the peptidoglycan layer.
3. Channel extends through the inner membrane (IM). Some viruses may use an IM receptor.
4. Viral DNA translocation into the host cytoplasm.
   
   

Gram(+) hosts:

1. Attachment to a host cell wall receptor.
2. Virion-associated exolysin (if present)hydrolyzes the peptidoglycan layer.
3. ? Channel formation or tunneling of a way through the host cell wall ?
4. Viral DNA translocation into the host cytoplasm.