Final answer:
Viruses that infect bacteria are referred to as bacteriophages, which may use a lytic or lysogenic cycle to replicate within the bacteria, with T4 and lambda phages serving as examples of these types.
Step-by-step explanation:
Viruses that infect bacteria are referred to as bacteriophages. Bacteriophages, also simply known as phages, have a specific lifecycle that includes binding to bacterial cells, injecting their genetic material, and potentially hijacking the cell's machinery to replicate themselves. The phage infection can be productive, resulting in new virions being assembled. Depending on the phage, this may occur through a lytic cycle, where the bacterium is lysed and destroyed to release the newly formed phages, or a lysogenic cycle, where the phage genome integrates into the bacterial genome to replicate along with the cell until it becomes active. An example of a lytic bacteriophage is T4, which infects the bacterium Escherichia coli, whereas the λ (lambda) phage, which also infects E. coli, can replicate as a temperate bacteriophage in the lysogenic cycle.