Microbiology Lab Excercise 12 - Gram Negative Bacilli


E. coli - on blood agar - non hemolytic

E. coli - on EMB, showing a metallic green sheen

Proteus - Members of the genus Proteus will swarm at certain intervals and produce a pattern of rings due to their motility. This photograph shows swarming of Proteus mirabilis on DNase agar

E. coli and a non-lactose fermentation - MacConkey agar inoculated with lactose-fermenting Escherichia coli (at left) and non-lactose-fermenting Proteus (at right). Lactose-fermenting bacteria appear bright pink, while non-lactose-fermenting bacteria appear colorless. This demonstrates the differential nature of MAC agar.