Question

Define plaque, lysogeny, and prophage.

Short answer

Question: Define the terms plaque, lysogeny, and prophage in the context of bacteriophages and their interaction with bacterial cells. Answer: A plaque is a visible, clear area on a bacterial lawn formed due to lysis of bacterial cells by bacteriophages. Lysogeny is a relationship between a bacteriophage and its host, where the bacteriophage integrates its genetic material into the host's genome without causing immediate cell lysis. A prophage is the integrated viral genetic material in a bacterial host's genome during the lysogenic cycle, which can be activated under certain conditions to enter the lytic cycle, causing cell lysis and release of new bacteriophages.

Step-by-step solution

Plaque

A plaque is a visible, clear area on a bacterial lawn (a uniform layer of bacterial cells on the surface of an agar plate) that results from the lysis (destruction) of bacterial cells by bacteriophages (viruses that infect bacteria). This area forms as a consequence of the bacteriophages infecting surrounding bacterial cells, multiplying, and then lysing (breaking open) the cells, releasing new bacteriophages to infect more cells, and eventually forming a visible clear zone on the bacterial lawn.

Lysogeny

Lysogeny is a type of relationship between a bacteriophage and its host (a bacterial cell) where the bacteriophage integrates its genetic material (DNA or RNA) into the host's genome without causing immediate lysis (destruction) of the host cell. In this state, the bacteriophage is referred to as a prophage (see below), and the host cell is called a lysogen. The prophage is passively replicated along with the host genome, so that when the host cell divides, the prophage is passed on to the daughter cells. Under certain conditions, such as environmental stress or damages to the host's DNA, the prophage can be triggered to exit the lysogenic cycle and enter the lytic cycle, leading to cell lysis and the release of new bacteriophages.

Prophage

A prophage is the integrated DNA or RNA of a bacteriophage within a bacterial host's genome during the lysogenic cycle. In this form, the viral genetic material is replicated and passed on to future generations of bacteria as the host cell replicates, without causing immediate harm to the host. Prophages can be activated under certain conditions to exit this dormant state and enter the lytic cycle, leading to the production of new bacteriophages and subsequent lysis of the host cell.