Some bacteria have an enzyme called nitrate reductase that can convert nitrate to nitrite. Some also have an enzyme called nitrite reductase that can convert nitrite into nitrogen gas. This medium is used to determine whether the microbe has the enzyme nitrate reductase. If it is present, the medium will also allow determination of the presence of the second enzyme, nitrite reductase.<\/p>\n\n\n\n
If a bacterium producing nitrate reductase is grown in a medium containing nitrate, the enzyme converts the nitrate to nitrite. Nitrite reacts with certain chemicals to yield a red-colored product.<\/p>\n\n\n\n
If the bacterium also produces nitrite reductase, nitrogen gas will be liberated. Bubbles collecting in an inverted Durham tube indicate that nitrogen gas has been produced.<\/p>\n\n\n\n
The medium used is nitrate broth with Durham tube, a nutrient broth with potassium nitrate added. The inverted Durham tube is placed in the medium as a trap for any nitrogen gas that might be generated.<\/p>\n\n\n\n
For information on how to detect nitrate and nitrite reductase activity, refer to the nitrate reduction test<\/a>.<\/p>\n\n\n\n
\n\n\n\nVUMIE is the flight simulator of microbiology labs.<\/h2>\n\n\n\n