Introduction: Many introductory bacteriology labs involve students growing bacteria cultured from the air, their skin, or on objects in the classroom on nutrient agar.
A follow-up to this activity is to try to identify the genus or even species of the bacteria based on unique metabolic properties. These properties allow bacteria to utilize a variety of energy sources. Additionally, they allow you to selectively grow bacteria in various media. All of the media listed below are availiable from Carolina Biological Supplies.
 
 

Characteristics	Media	Positive Results	Negative Results
glucose fermentation	nutrient broth + 0.5% glucose + phenol red + Durham tube	yellow for acid production bubble for gas production	red color no bubble
lactose fermentation	nutreint broth + 0.5% lactose + phenol red + Durham tube	yellow for acid production bubble for gas production	red color no bubble
starch digestion	starch agar + Gram's iodine-to be poured on after incubation)	blue/black streak	uniform color
catalase production	nutrient agar + H2O2-to be poured on after incubation)	bubbles	no bubbles
DNA digestion	DNase test agar or nutrient agar + sperm from fish or sea urchin and HCl	clear streak	cloudy (DNA ppt.)
H2S production from cysteine	SIM(Sulfide Indole Motility) + inoculating needle to stab media	black line	no line
Indole production from tryptophan	Tryptone or trypticase soy broth + Kovacs reagent-to be added after incubation	red ring	yellow or light brown ring
urea digestion	urea broth	purple	urine color (no change)
lipid digestion	sprint blue agar	deep blue zone	pale blue zone
casein digestion (tests for the presence of milk proteinase)	skim milk agar	clear streak	no visible steak

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