How do you differentiate between E-Coli and Enterobacter Aerogenes?
These two bacterial species are identical in many superficial ways. They both produce white colonies at 37 degrees Celsius on nutrient agar. They both ferment lactose producing acid and gas. They are both Gram negative and virtually identical microscopically. To distinguish them we must resort to biochemical tests. They metabolize sugars and other organic compounds, like Citrate, differently. Below are some of the tests we do to distinguish E. coli and E. aerogenes. Note how clearly they differ when we use biochemistry to tell them apart! Below on the left E. coli and Enterobacter aerogenes are growing on the surface of Eosin-Methylene Blue Agar. There is glucose in this medium which both bacteria metabolize. But they both produce different byproducts. E. coli produces a byproduct of glucose metabolism which reacts with the basic dyes in the medium producing a “green metallic sheen” in reflected light. Enterobacter produces normal colonies. The EMB test differentiates between E. coli a
