NITRATE REAGENT DISCS (Double Pack)

Description

The test involves detection of the enzyme nitrate reductase which causes the reduction of nitrate in the presence of a suitable electron donor to nitrite, which can be tested by an appropriate colorimetric reagent. Almost all Enterobacteriaceae reduce nitrate. Nitrate reagent discs when placed on suspected colony turn red-pink in case of nitrate reduction (positive reaction), when a drop or two of Part B (Rehydrating fluid) is added to the disc. Reduction of nitrate (NO3) to nitrite (NO2) and subsequently to nitrogen gas (N2) usually takes place under anaerobic conditions, in which an organism derives its oxygen from nitrate. Most facultative anaerobes can reduce nitrate in the absence of oxygen. This anaerobic respiration is an oxidation process in which inorganic substances furnish oxygen to serve as an electron acceptor to provide energy. The end product possibilities of nitrate reduction are many depending upon the bacterial species. The more common end product via nitrite reductionis molecular nitrogen. Depending upon environmental conditions, these products are usually not further oxidized or assimilated into cellular metabolism, but are excreted into the surrounding medium