What is the process called when a plasmid moves from one bacterium to another through a pilus?

The process referred to here is called conjugation. This is a specific mechanism of horizontal gene transfer in bacteria that involves direct cell-to-cell contact. During conjugation, a donor bacterium transfers genetic material, typically in the form of a plasmid, to a recipient bacterium through a specialized structure known as a pilus. The pilus acts like a bridge, facilitating the transfer of the plasmid and allowing the recipient to acquire new genetic traits, which can enhance its survival and adaptability.

Conjugation is significant in microbial genetics because it enables the spread of plasmids, including those that carry antibiotic resistance genes, across bacterial populations, which can have profound implications for public health and antibiotic efficacy. This distinguishes conjugation from other processes like transduction, where DNA is transferred via bacteriophages, and transformation, which involves the uptake of free DNA from the environment by a bacterium. Replication, on the other hand, refers to the process of copying DNA within a single cell, not the transfer between organisms.