In: Biology
Describe the steps in a bacteriophage and describe events that occur on an agar plate containing a bacterial lawn for a single bacteriophage particle to cause the formation of a plaque.
A) Steps in a bacteriophage lifecycle that helps it to infect a bacteria are:
1. Adsoprtion - The bacteriophage, with the help of it's spike proteins, adheres itself to the cell surface of the bacteria that allows the pathway for entrance of the viral proteins and genetic material in the cell.
2. Penetration - The viral DNA or RNA gets penetrated inside the bacterial host cell after the bacteriophage undergoes uncoating.
3. Transcription - The inserted genetic material then hijacks the replication and transcription-translation machinery of the host cell and makes it it's own. The transcription allows production of more new early and late replication proteins for the virus
4. Replication - The viral genetic material is replicated by the host cell machinery as it's own and more copies of the DNA is produced along with the separate production of the viral head and tail and spike proteins that are produced by trasncription.
5. Assembly - All the sunthesized proteins and genetic materials are assembled to form a complete infective bacteriophage inside the host cell. Multiple copies of such bacteriophages are made by assembly mechanism.
6. Release - The packaged bacteriophage then undergoes viral coating by the host cell membrane and then released by the host cell. This lytic mechanism kills the host cell.
One more possibility is the retaining of the viral genetic material as a prophage and remaining integrated into the host chromosome in a lysogenic phase.
B) The plaque occurs when the bacteriophage obtains a lytic cycle mechanism and releases virions of the host cell. The host cell dies and that creates a clear plaque on the agar plate.