What Is a Bacteriophage Virus?

Phage Viral Host Recognition, Lytic Replication & Lysogeny

Jun 9, 2008

This series of articles explores how viruses that exclusively infect bacterial cells recognize the hosts they parasitize and reproduce once the bacterium is infected.

Did You Know that Bacteria Can Come Down with a Virus?

Bacteriophages (aka phages) are a type of virus that preys upon bacterial cells. The reproduction of these parasitic acellular particles always involves death of the infected bacterium, when the viruses burst out, lysing their prokaryotic host cell.

How Does a Virus Find Its Host?

Whether it is an animal virus or a phage, most viruses infect only a certain type of host. And, since viruses are non-motile (can’t move on their own), coming into contact with the host occurs purely by chance.

Viral specificity is due to the affinity between proteins on the surface of the virus and corresponding glycoproteins on the surface of the host cell. If the virus happens to land on the right type of cell, it can enter and infect.

Bacterophages, which look much like War of the Worlds spaceships, have proteins in their tail fibers that attach to proteins on the surface of the prokaryotic bacterial cell. After recognition and attachment to the host, the phage injects its genetic material (DNA or RNA) into the host cell.

How Does a Virus Reproduce?

Sometimes a phage will immediately take over the cell that it has infected. This is called lytic replication, a cycle which ends when the new phages burst out, killing the host bacterium.

But sometimes the viral genetic material remains hidden and inactive in the bacterial DNA, allowing the host to reproduce. Each time the infected bacterium duplicates its DNA (nucleic acid) and divides, it also creates another copy of the viral nucleic acid; a very sneaky and effective tactic for creating a huge number viruses from one initially infected bacterial cell.

The following three articles explore the world of the bacteriophage in more detail.

Article Series on Viral Reproduction

Phages are a special type of virus that exclusively infects bacterial cells. Here's how they recognize, take over and ultimately kill their host bacteria.

Bacteriophages reproduce by commandeering a bacterium and eventually killing it. But sometimes, through lysogenic replication, the phage bides it time and doesn't immediately take over its host.

Sometimes viral replication results in the death of the bacterium shortly after infection. In other instances the viral DNA lies in wait within the host’s genome. This article explores tactics of the phage.

More Information on Microbes

Sources

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