An inoculum from a pure culture is transferred aseptically to a sterile tube of nitrate broth containing an inverted Durham tube. The inoculated tube is incubated at 35-37 C for 24 hours and the results are determined. A positive test for both enzymes consists of a turbid (cloudy) broth with pronounced gas bubbles trapped in the Durham tube. If results like this are not observed, testing for the individual enzymes can be done through addition of reagents, with a positive test indicated by the broth turning red.