There are many biochemical tests that can be used to help identify bacteria. 

• Since bacteria will react differently to these tests it is much like the bacterial "fingerprint". 
• These are a few biochemical tests that can be run. 

In the isolation process of bacteria, a microbiologist can use a number of different media. 

• A basic nutrient agar will grow any bacteria and is used to grow cultures in laboratory settings.  If the microbiologist wants to isolate certain species they can use a number of different media types. 
• In addition to basic nutrients, differential media contains one or more components that can be used by some microbes but not others.  Selective media contains one or more components that suppress the growth of some microbes without affecting the growth of others.  With the use of these different media, one can isolate particular species in a relatively short amount of time. 
• Manitol salt agar (MSA) can be used to grow Halophiles.  It is both a selective and differential media.  It uses salt as the selective agent and a pH indicator of sugar fermentation to differentiate species.   Only a few bacteria will ferment the sugar in the plate and turn the plate yellow.  (Staphylococcus aureus is one such species.)
• Eosin methylene blue agar (EMB) is also selective and differential media.  It selects for gram negative enteric bacteria and has an indicator that will turn metallic green in the presence of E. coli.

Microbial metabolic processes are complex, but can be very helpful in identifying bacteria. 

• Some bacteria ferment simple carbohydrates and produce acid or gaseous end products. 
• An indicator in the solution will change from red to yellow in the presence of acid and the small tube (Durham tube) in the solution will collect any gas that is produced.  Using this knowledge, it makes identification easier. 
• To score simple carbohydrate fermentation, use the following key: A - acid production, a - slight acid production, G - large gas bubble, g - small gas bubble, N - no reaction. 
• Another type of carbohydrate is starch.  This is a complex carbohydrate and is more difficult for bacteria to metabolize.  To identify starch digesters, we can grow the bacteria on a starch agar. 
• To score this reaction we use iodine.  Iodine will react with the starch in the plate turning it black.  If there is no starch there will be a ring around the bacteria, indicating that the bacteria digested the starch.