Final answer:
When a bacterium acquires a new trait from a temperate phage, lysogenic conversion has occurred. This process involves the integration of phage DNA into the bacterial genome, and can result in new phenotypic traits for the bacterium, such as increased virulence due to toxin gene expression from the phage.
Step-by-step explanation:
When a bacterium acquires a new trait from a temperate phage, lysogenic conversion has occurred. Temperate phages can undergo both the lytic and the lysogenic cycles. During the lysogenic cycle, the phage DNA is integrated into the host bacterium's genome, forming a prophage. The bacterial host with a prophage is termed a lysogen.
Genetic material from the phage can confer new properties to the bacteria, such as toxin production leading to increased virulence. For example, the bacteria Vibrio cholerae and Clostridium botulinum become more virulent due to phage-encoded toxin genes.
The phenomenon where new genes introduced by the phage change the host's phenotype is referred to as lysogenic conversion or phage conversion.Environmental factors such as UV exposure can induce the prophage to excise from the bacterial chromosome and enter the lytic cycle, potentially leading to specialized transduction as the phage transfers specific bacterial genes to another host.