Final answer:
Horizontal gene transfer, specifically conjugation, is the mechanism responsible for the transmission of antibiotic resistance genes between microorganisms.
Step-by-step explanation:
The transmission of antibiotic resistance from one microorganism to another is most commonly achieved through horizontal gene transfer. This process allows for the transfer of genes responsible for antibiotic resistance between different microorganisms. One of the mechanisms of horizontal gene transfer is conjugation, where genes are transferred from one bacterium to another via a hollow tube called a pilus.