What kind of objects can be qualified as artifacts? How do we distinguish such objects?
An artifact in biology usually refers to experimental error or other spurious results. In the context of microbiology, you will get artifacts if, for example, you sneeze on the plate you are growing a colony on.
The term is generally used for any result that is not actually true but stems from bad analysis or experimental procedures. Take, for example, this definition from biology-online.com: