What are bacteriophages? Bacteriopahges, or phages, are viruses that infect bacteria and archaea. They were discovered in 1915 by Frederick W. Twort and the name "bacteriophage" means bacteria-eater.
Just like how T and B cells can only rescue cells with a certain receptor, phages can only affect certain strains of bacteria, but there are thousands of variations of bacteriophage. The structure of a phage consists of DNA or RNA inside a protein capsid (see image to the right). |
Bacteriophage Life cycle The phage life cycle begins when a phage attaches to a bacterium, penetrates the cell membrane, and releases its DNA or RNA into the host cell. From here, there are several possible life cycles but the two main ones are the lytic and lysogenic cycles.
Lytic bacteriophages invade a cell, produce phage parts inside the host cell, assemble into new phages, then lyse the host cell's membrane to escape and continue the cycle. Lysogenic phages invade the cell and inject its genetic material, but instead of reproducing inside of the cell, the phage genes attach to the host cell's DNA. After the bacterium multiplies several times, the phage genes are activated, then bacteriophage parts are mnufactured. The phages assemble, destroy the cell, then exit and repeat the life cycle. Click here to read about and watch a video on the phage life cycle. |