What process involves the transfer of genetic material between bacterial cells through direct contact?

Conjugation is the process that involves the direct transfer of genetic material between bacterial cells through physical contact, often mediated by a structure called a pilus. In this process, one bacterium (the donor) transfers a copy of its plasmid or part of its chromosomal DNA to another bacterium (the recipient). This type of horizontal gene transfer allows for genetic diversity and can lead to the spread of traits such as antibiotic resistance among bacterial populations.

In contrast, transduction involves the transfer of genetic material via bacteriophages (viruses that infect bacteria), where DNA is accidentally packaged into a virus and delivered to another bacterium. Transformation refers to the uptake of free-floating DNA from the environment by a bacterial cell, without direct contact. Replication is the process by which DNA is copied before cell division and does not involve the transfer of DNA between cells. Thus, conjugation specifically pertains to the direct transfer of DNA through cell-to-cell contact, making it the correct answer.