Bacteriophages are bacteria infecting viruses. They are also called ‘phage’ or simply bacterial viruses as any group of viruses that infect bacteria are referred to as Bacteriophage. A bacteriophage is a virus that parasitizes bacteria and reproduces inside it. They are of different shapes and show genetic variations. They may contain DNA or RNA as genetic material and may have gene counts ranging from four to several thousand. The name bacteriophage describes an entity’s bactericidal ability and it translates to ‘’bacteria eater’’ in English.
Characteristics of a Bacteriophages
- Several varieties of bacteriophages exist in the environment but one type can infect only one type or a few types of bacteria.
- Like all other viruses, they are simple organisms consisting of a core of genetic material surrounded by a protein capsid.
- They are classified into several Virus families. Examples include Inoviridae, Microviridae, Rudiviridae, and Tectiviridae.
- The genetic material can either be DNA or RNA in the bacteriophages.
- After infecting a cell, it completely takes control of the host cells and stops it from producing bacterial components, and forces it to produce viral components.
- They eventually bring about the lysis of the host bacterial cell.
- They are also involved in a process called transduction, in which Bacteriophages occasionally remove a portion of their host cell’s DNA and transfer this DNA into the genome of new host cells.
- It is made up of a protein coat known as a capsid, which encapsulates the genome. It consists of a polyhedral head.
- The capsid is made up of many capsomeres. The size and shape vary in different species.
- It may be enveloped or nonenveloped and have different shapes such as rod-shaped, filamentous, isometric, etc.
- The genome consists of ss or ds DNA or RNA, which is linear or circular. The genome codes for proteins ranging from 4 to 100. MS2 bacteriophage genome codes for 4 proteins. The largest genome found in a bacteriophage is 735 kbp.
- The tails may be long or short, contractile or noncontractile. Tail fibers are present, it helps in anchoring the virus to the bacterial cell wall.
Importance of Bacteriophages
- Bacteriophages are used as antibiotics against bacteria due to the same mode of action.
- They are used in the food industry to kill bacteria in meat or cheese products.
- Bacteriophages are used for diagnostic purposes.
- They act as a model in research and studies.
- Used as a cloning vector in genetic recombination techniques.