Bacteriophages are all made up of a nucleic acid molecule encased in a protein framework. A bacteriophage infects the host cell by attaching itself to a susceptible bacterium. Following infection, the bacteriophage hijacks the bacterial cell’s biological machinery, forcing the cell to create viral components instead of bacterial components.

In a process known as lysis, new bacteriophages assemble and burst out of the bacteria. During the infection process, bacteriophages sometimes take a part of the bacterial DNA from their host cells and subsequently transfer this DNA into the genome of new host cells. Transduction is the term for this procedure.

A Quick Guide on Bacteriophage 

Now we will take a deeper look at what bacteriophage is, its life cycle stages and lastly, we will read about the structure of bacteriophage.

What is bacteriophage

A bacteriophage, also known as a phage or a bacterial virus, is a virus that infects bacteria. Frederick W. Twort in the United Kingdom (1915) and Félix d’Hérelle in France discovered bacteriophages separately (1917). D’Hérelle coined the term bacteriophage, which means “bacteria eater,” to describe the agent’s bactericidal ability.”Archaea, which are single-celled prokaryotic organisms, may also be infected by bacteriophages.

 Characteristics- 

There are thousands of different forms of phage, each of which can exclusively infect one or a few species of bacteria or archaea. Inoviridae, Microviridin, Rudiviridae, and Tectiviridae are only a few of the viral families that phages belong to. Phages, like other viruses, are basic creatures with a genetic material (nucleic acid) core wrapped by a protein capsid. The nucleic acid may be double-stranded or single-stranded, and it can be DNA or RNA. An icosahedral (20-sided) head with a tail, an icosahedral head without a tail, and a filamentous form are the three fundamental structural types of phage.

Life cycle stages- 

A phage binds to a bacterium and inserts its genetic material into the cell during infection. After that, phages typically follow one of two life cycles: lytic (virulent) or lysogenic (lysogenic) (temperate). Lytic phages use the cell’s machinery to produce phage components. They lyse the cell after that, releasing more phage particles in the process. Lysogenic phages insert their nucleic acid into the host cell’s chromosome and proliferate as a unit with it without killing the cell. Lysogenic phages may be made to follow a lytic cycle under particular circumstances.

Other life cycles occur, such as pseudolysogeny and chronic infection. A bacteriophage enters a cell but neither co-opts cell-replication machinery nor integrates stably into the host genome in pseudolysogeny. Pseudolysogeny occurs when a host cell experiences unfavourable growth circumstances, and it seems to play a key role in phage survival by allowing the phage genome to be preserved until the host’s growth conditions improve. New phage particles are created continually over lengthy periods of time in chronic infection, although there is no visible cell death.

Structure of bacteriophage

Phages come in a variety of forms and sizes. The group of tailed phages with a dsDNA genome has been investigated the most and is also the biggest. Tailed phages have three major components: a capsid that contains the genome, a tail that acts as a pipe during infection to ensure that the genome is transferred to the host cell, and a special adhesive system (adsorption apparatus) at the very end of the tail that recognizes the host cell and penetrates its wall. For phage reproduction, cell resources are utilised.

The functioning phage is the product of a multistep process that begins with the host cell producing all of the required proteins upon infection: capsid, portal, tail, scaffolding, terminase, and so on. 

The head-to-tail contact breaks one of the fivefold axes, causing the capsids of dsDNA phages to exhibit fivefold or icosahedral symmetry (HTI). A dodecameric portal protein (PP) inside the capsid is the major component of the HTI. The PP stands for the DNA-packaging motor, a critical component of these nano-machines. The HTI also comprises oligomeric rings of head completion proteins, which serve two purposes-

1. Providing an additional interface to ATP molecules, which supply energy for DNA packing, and providing an additional interface to ATP molecules.
2. The portal protein and the tail are then connected. Some HTIs also function as valves, closing the exit channel to prevent genome leaking from the capsid but opening after the phage has been linked to the host cell.

Also, Bacteriophages, like all other viruses, are very species-specific in their host cell. Bacteriophages only infect a particular bacterial species or even specific strains within that species. All bacteriophages have the same fundamental structure. They are made up of a nuclear core surrounded by a protein capsid.

Conclusion-

In this article we read what bacteriophage is, its characteristics, its life cycle stages and lastly, structure of bacteriophage. Bacteriophages (BPs) are bacteria-infecting viruses that destroy bacteria without harming human or animal cells. As a result, it is thought that they may be used to treat bacterial infections alone or in conjunction with antibiotics. They are the most prevalent biological agent on the planet, and they are pervasive in the environment. Their size, appearance, and genetic structure are all quite varied.