Final answer:
Gene transfer in prokaryotes occurs mainly through three mechanisms: transformation, which is the uptake of DNA; transduction, where a virus transfers genetic material; and conjugation, where direct cell-to-cell contact allows DNA exchange via a pilus.
Step-by-step explanation:
Microbiology students and scientists alike recognize that horizontal gene transfer is a pivotal method by which bacteria can gain new traits, including resistance to antibiotics. The three classic mechanisms of gene transfer include:
Transformation: This process involves a bacterium taking up DNA from its environment. The DNA can either remain as a separate plasmid or integrate into the bacterial chromosome.
Transduction: In this mechanism, a virus or bacteriophage carries and injects genetic material from one bacterium into another. The DNA that is transferred can be a mix of viral DNA and DNA from the previously infected host.
Conjugation: This is the direct transfer of DNA between two bacterial cells. It involves the formation of a mating bridge, or pilus, after one bacterial cell extends a sex pilus to draw another cell close enough for the transfer of the genetic material.
In addition to these three methods, a fourth method involving gene transfer agents (GTAs) is also notable for transferring random DNA segments between prokaryotes. Nevertheless, transformation, transduction, and conjugation remain the fundamental mechanisms that students of microbiology must understand when studying the ways prokaryotes exchange genetic material and evolve.