Biochemical tests are the quickest and easiest tests for identifying bacteria because they use deductive principles to reduce the number of possible species present very quickly. Additionally, because bacteria are microorganisms, visual identification is not always possible, and is never easy. Genetic testing is possible for some well-known bacteria, but it is expensive and time consuming.
A simple biochemical test for bacteria is the catalase test. One of the best ways to reduce the pool of potential bacteria species is to determine whether the species in question is anaerobic, meaning that it does not use oxygen in its metabolism. To perform the test, technicians expose a bacteria-laden slide to a small amount of hydrogen peroxide. The technicians then observe the slide with the help of a microscope to look for signs of bubbles. Bubbles indicate that the bacteria are capable of metabolizing oxygen and are not anaerobic bacteria.
Microbiologists have many different biochemical tests at their disposal that can help them to deduce the identity of bacteria. Often, more than one test is required to identify a specimen positively. The source of the bacteria may provide many clues to its identity. Technicians that routinely test similar samples often become skilled at using the least amount of tests possible.