Created by
Paul A. Gulig, Ph.D.
Department of Molecular Genetics and Microbiology
with assistance from
David Brumbaugh
What is the significance of the two colony types?
B. Type 2 is lactose-positive, and type 1 is lactose-negative.
Yes, the red color shows that acid was produced from lactose, meaning the bacteria could utilize lactose as a carbon source.
In this contrived laboratory exercise there are no lactose-negative pathogens to differentiate. Colony type 1 is a mutant E. coli provided in the mixture for contrast with the lactose-positive bacterium in colony type 2.