Gastrointestinal bacteria generate nitric oxide from nitrate and nitrite

Area of Science:

• Microbiology
• Gastroenterology
• Biochemistry

Background:

• Soil denitrifying bacteria produce nitric oxide (NO) during the nitrogen cycle.
• The production of NO by commensal gut bacteria remains largely uncharacterized.
• Nitric oxide plays crucial roles in various physiological processes, including gastrointestinal integrity.

Purpose of the Study:

• To investigate the potential of human fecal matter and representative gut bacteria to generate nitric oxide (NO).
• To explore the influence of nitrate and nitrite availability on NO production by gut microbiota.
• To assess in vivo NO generation within the gut lumen.

Main Methods:

• Chemiluminescence assay to quantify NO production.
• Anaerobic incubation of bacteria with or without nitrate/nitrite.
• In vivo measurement of luminal NO levels in germ-free, conventional, and mono-associated rats.

Main Results:

• Human feces supplemented with nitrate or nitrite demonstrated NO generation.
• Lactobacilli and bifidobacteria significantly produced NO from nitrite, with limited production from nitrate.
• Escherichia coli, Bacteroides thetaiotaomicron, and Clostridium difficile showed negligible NO production.
• In vivo studies confirmed NO generation in conventional rats but not in germ-free or lactobacilli-mono-associated rats.

Conclusions:

• Anaerobic gut flora can generate nitric oxide (NO) in the presence of nitrate or nitrite.
• Specific bacterial groups like lactobacilli and bifidobacteria are key contributors to gut NO production.
• Further research is needed to elucidate the biological significance of gut-derived NO in maintaining gastrointestinal health.