This is a lactose test. I'm trying to find the identity of 2 bacteria that were in a sample I was given last week. I did a gram stain (couldn't take a picture of that) and found a gram possitive cocci (little round things) and gram negative bacillus (worm looking things). The stain told me what test path I should take. This was the lactose test on the (-) bacillus. The tube was purple to start so the color change indicates that the bacteria produced an acid from the lactose and the bubbles in the glass tube in the middle tell me that gas was produced. This is a positive result so next I need to see if it can use citrate! Wee!