Refinement of the Griess method for measuring nitrite in biological samples

Area of Science:

• Biochemistry
• Microbiology
• Analytical Chemistry

Background:

• Nitric oxide (NO) is a crucial signaling molecule involved in physiological and pathogenic processes.
• Accurate measurement of NO is challenging due to its reactive nature.
• Existing methods for NO quantification have technical limitations.

Purpose of the Study:

• To improve the accuracy and accessibility of measuring nitric oxide (NO) production.
• To present an enhanced method for indirect NO quantification using bacterial whole-cell extracts.
• To offer an alternative to existing NO measurement techniques.

Main Methods:

• Utilized whole-cell extracts from Escherichia coli engineered to lack specific nitrite reductases.
• Employed the Griess reaction for the colorimetric detection of nitrite, a product of nitrate reduction.
• Investigated the effect of osmotic stress on nitrate reductase expression in E. coli.

Main Results:

• The modified E. coli extracts provided more precise indirect measurement of NO via nitrate reduction compared to previous methods.
• Osmotic stress was found to downregulate nitrate reductase expression, offering an alternative approach.
• The developed method avoids nitrate reconversion and serves as an alternative to cadmium, purified enzyme, or salicylic acid-based assays.

Conclusions:

• A simplified and precise method for indirect NO measurement using engineered E. coli is established.
• This technique is applicable to diverse samples, including living organisms, soil, and microbiological contexts.
• The improved method offers a valuable alternative for NO quantification in research and diagnostics.