A large domain of microorganisms, potentially consisting of millions of different species.

Bacteria can affect human life in positive or negative ways. Some bacteria cause sexually transmitted infections (STIs); common examples include chlamydia, gonorrhea, and syphilis. Other strands of bacteria play a beneficial role in regulating the pH levels of the vagina, which helps to limit the incidence of yeast infections and other conditions.

Many lubricants include ingredients that prevent or limit bacterial growth. This allows for a long shelf life and ensures that the lube is safe for internal use. To prevent bacterial STIs, you should always use condoms when having penetrative sex.