Distribution and activity of nitrate and nitrite reductases in the microbiota of the human intestinal tract

The human intestinal microbiota plays a vital role in health. One of the most protective benefits is the bacterial nitrogen metabolism of gut bacteria, which reduces nitrate (NO3–) and nitrite (NO2–) to ammonia or nitric oxide, preventing the formation of carcinogenic nitrosamines. In this study, we shed light on the gut bacterial NO2–/NO3– degradation, its efficacy, and the effects on the steady-state NO2– concentration in the human colon. Highly abundant gut bacteria that represent the most prominent phyla were analyzed for their potential to reduce NO2– or NO3–. Escherichia coli showed the greatest efficiency, which indicates a key role in the detoxification and the prevention of nitrosamine formation. Species of the genera Bacteroides and Phocaeicola also contributed to NO2– reduction due to their high abundance. The total activity of stool samples was about 620 µmol NO2– h-1, indicating that NO2– concentration in the human stool should be very low. We also show that bacterial NO2– ..., , # Distribution and activity of nitrate and nitrite reductases in the microbiota of the human intestinal tract

Dataset DOI: [10.5061/dryad.stqjq2cf4](10.5061/dryad.stqjq2cf4)

## Description of the data and file structure

General experimental overview:

This dataset contains the raw data and derived kinetic parameters used to assess nitrite and nitrate reduction by intestinal bacteria under anaerobic conditions. Experiments were performed in buffered brain heart infusion (BHI) or modified SHIME medium at 37°C under an N~2~/CO~2~ atmosphere. Optical density (OD~600~), pH, and nitrite/nitrate concentrations were measured at regular time intervals to determine growth and reduction kinetics. Nitrite was quantified colorimetrically using the Lunge reagent method (absorbance at 540 nm), and nitrate was determined by HPLC. Data were obtained from three biological replicates with three technical replicates each, unless otherwise indicated.

\----------------------------------------------------..., Human subjects de-identification statement: All human-derived fecal samples used in this study were obtained in an anonymized form from collaborating institutions. No personally identifiable information (PII) or metadata that could link the samples to individual donors was provided to, or collected by, our laboratory. The samples were used exclusively for microbial community and biochemical activity analyses, and no human genetic or clinical data were generated. Because donor identification was not possible at any stage of the study, no additional de-identification procedures were necessary.
The use of anonymized fecal material complied with institutional ethical standards and applicable data protection regulations.