Final answer:
Horizontal gene transfer is the process where bacteria exchange genetic material via transformation, transduction, or conjugation. Conjugation is particularly responsible for spreading antibiotic resistance among bacteria.
Step-by-step explanation:
The transfer of genes by a mechanism that does not involve reproduction is termed Horizontal Gene Transfer. Within this broad category, there are several mechanisms through which bacteria can exchange genetic material:
Specifically, the mechanism naturally responsible for the spread of antibiotic resistance genes within a bacterial population is conjugation, which facilitates the transfer of plasmids carrying resistance genes between bacterial cells.