Lab method
Nitrate reduction test
Red after reagents = nitrate reduced
High-yield clue
Red color after adding the nitrate reagents means nitrate was reduced, a hallmark of Enterobacterales.
Overview
A biochemical concept testing whether an organism reduces nitrate to nitrite (or further); reagents A and B turn red when nitrite is present.
Classification
- Metabolic reduction concept
- Detects nitrate reductase
- Sulfanilic acid / naphthylamine readout
Lab & identification clues
- Red after reagents = nitrate reduced to nitrite
- No color, then zinc red = true negative
- No color after zinc = reduced past nitrite
- Enterobacterales are typically positive
Associations
- Enterobacterales metabolism vocabulary
- Anaerobic respiration study framing
- Gram-negative identification
Commonly confused with
- Citrate utilization test
- Oxidase test
Your notes
Original concept summary for coursework. Sources checked: OpenStax Microbiology 2e and NCBI Bookshelf Medical Microbiology; reviewed 2026-06. Describes vocabulary and interpretation concepts only; not a lab protocol and not for handling specimens or identifying patient isolates.