Nitrate Test - Microbiology Class - Podcast (CC)
In this video, we cover the Nitrate Reduction Test, a critical test used to determine if bacteria can reduce nitrate (NO₃⁻) to nitrite (NO₂⁻) or even further to nitrogen gas (N₂). This test is valuable in differentiating facultative anaerobes from obligate aerobes.
Key points covered:
Purpose: Determine if bacteria use nitrate as the final electron acceptor in anaerobic respiration.
Procedure: After inoculating the bacteria into nitrate broth, the culture is incubated for 48 hours. Reagents A (sulfanilic acid) and B (alpha-naphthylamine) are added to detect nitrite. If no red color appears, zinc powder is added to detect unreduced nitrate.
Positive result:
Red color after adding reagents A and B indicates the presence of nitrite, showing partial nitrate reduction.
No color change after adding zinc indicates nitrate reduction beyond nitrite to nitrogen gas.
Negative result: A red color after adding zinc indicates nitrate was not reduced, showing a negative result for nitrate reduction.