Yeah man, I feel you. You know bacteriophages? Yeah they sound scary, right? They look scary, too, here:
When I first saw that, I was like nah, I do not want these biological entities in my body, look at dem legs and how spider-like they look. But they’re the good guys. Phages are bacterial predators made up of either DNA or RNA and can persist only in a host, not alone. They carry genes on their own genomes that alter bacterial physiology, but bacteria also have primitive immune systems to recognize phage, which results in an arms race between bacteria and the phage.
Let me tell you what these bad boys do. There are 3 types: Virulent, Temperate and Filamentous, which can either 1) kill/lyse (rupture), 2) integrate into host genomes and then replicate or 3) simply replicate and direct the host to shed new phage particles without killing causing cell death, respectively.
In the interest of time and space, I will show you how the Virulent type, a T4 Bacteriophage kills bacteria, specifically Escherichia coli (E.coli). First, they attach to host cell proteins and receptors that are normally used for bacterial purposes like nutrient uptake and conjugation. Then the phage takes advantage of host proteins and injects its own DNA into the host cytoplasm. Here’s the order of gene expression as the phage takes control of the host machinery for its own purposes and basically manipulates the bacteria to commit suicide (COOL RIGHT?!) :
Early phage genes are usually expressed by the bacterial RNA polymerase. They usually encode genes to disable the various bacterial immunity factors and redirect host protein and RNA synthesis to serve the phage.
Middle genes typically are expressed by an RNA polymerase that is under phage control. The host RNA polymerase is usually disabled at this point. Among these genes are typically those involved in phage DNA replication after degradation of host DNA and activation of late genes.
Late genes usually encode the capsid and tail proteins as well as the group of genes necessary for lysis (rupture) of the bacterial cell during phage escape.
There are a ton of other details but NOT SO SCARY NOW, RIGHT?!
Much love :)