Bacteria reproduce mainly through a process called binary fission, which is a form of asexual reproduction. However, they do have mechanisms that allow for the exchange of genetic material which can be thought of as a kind of sexual reproduction. This process is known as horizontal gene transfer.
There are three main methods of horizontal gene transfer in bacteria: transformation, transduction, and conjugation. In transformation, bacteria take up naked DNA from their environment. In transduction, a bacteriophage (a virus that infects bacteria) transfers genetic material between bacteria. In conjugation, two bacteria connect through a structure called a pilus and transfer genomic material directly.
While these processes don’t involve the formation of gametes like in sexual reproduction seen in higher organisms, they do increase genetic diversity in bacterial populations, which is essential for adaptation and evolution.