Which of the following require physical contact between two bacterial cells for DNA transfer?

When a virus enters a host cell, it hijacks the host's cellular machinery to replicate itself. Viral genes direct the host cell to transcribe and translate viral proteins instead of its own normal proteins. This redirection alters the host’s metabolic and genetic activities, often shutting down regular cellular processes. The host cell becomes a “viral factory,” producing viral components that are then assembled into new virions. This process can damage or kill the host cell, depending on the type of virus and replication strategy, and is a defining characteristic of viral infections, distinguishing them from non-infectious intracellular activities.

Not all mutations are harmful to the cell. Mutations are changes in the DNA sequence, and their effects depend on the location and nature of the change. Some mutations are neutral, causing no noticeable effect on cellular function. Others can be beneficial, providing an adaptive advantage under specific environmental conditions, such as antibiotic resistance in bacteria. Harmful mutations do exist and can disrupt protein function, leading to cell dysfunction or death, but the presence of a mutation does not automatically equate to harm. The impact of a mutation is determined by how it affects gene expression and protein activity.