Abstract
Despite recent interest in functional food merits of dietary nitrate, there is a paucity of information on its utility as a pre-biotic for the enrichment of health-promoting oral bacteria. The objective of this investigation was to observe the dynamic change in the denitrifying oral microbiome of healthy human volunteers following supplementation of nitrate enriched diet for a period of two-weeks. The study involved isolation, identification and comparison of nitrate-reducing oral bacteria of five human volunteers before and after supplementation of a nitrate-rich diet. This was further correlated with salivary nitrite contents to understand denitrification efficacy with prolonged dietary nitrate supplementation. A total of 153 bacterial strains were isolated from baseline (BSL) samples of healthy participants, i.e. before supplementation and after dietary nitrate supplementation (ADNS); 32 out of these isolates could be confirmed to be nitrate-reducers. Although members of Firmicutes viz., Streptococcus salivarius, Streptococcus parasanguinis and Actinobacteria viz., Rothia mucilaginosa were present in both BSL and ADNS samples, the relative abundance of Actinobacteria was higher and Firmicutes was lower in ADNS in comparison to BSL samples. Moreover, Proteobacteria were found only in ADNS and not BSL samples. Interestingly, these changes in nitrate-reducing microbiome were correlated with higher salivary nitrite levels on day 14 in comparison to day 1 following acute supplementation of dietary NO3−. Thus, it is being hypothesized that Rothia, Neisseria and Streptococcus spp. which appeared following 14 days of nitrate supplementation, could be more efficient towards reducing nitrate and boosting salivary nitrite levels.
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Abbreviations
- ADNS:
-
After dietary nitrate supplementation
- ANA:
-
Anaerobic Agar
- BSL:
-
Baseline
- MRS:
-
De Man Rogosa and Sharpe agar
- NA:
-
Nutrient agar
- NO:
-
Nitric oxide
- NO2 – :
-
Nitrite
- NO3 – :
-
Nitrate
- PCR:
-
Polymerase chain reaction
- RCA:
-
Reinforced clostridial agar
- rRNA:
-
Ribosomal ribonucleic acid
- TSA:
-
Tryptic soy agar
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Acknowledgements
We express our sincere gratitude to the “University Institute of Engineering and Technology (UIET), Panjab University (PU), Chandigarh” and “CSIR-Institute of Microbial Technology (CSIR-IMTECH), Chandigarh” for their invaluable assistance and exceptional laboratory analysis.
Funding
This work was supported by “Defence Institute of High Altitude Research (DIHAR), Defence Research and Development Organization (DRDO), Ministry of Defence, Govt. of India, C/O 56 APO, Leh-Ladakh, Pin-194101, India”.
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Nitish Kumar contributed to the design of the research, collected samples, conducted lab work and conducted the analysis. Madhu Khatri and Shweta Saxena conceived the idea of this research work and as a supervisor contributed to the conceptualization and implementation of the research. Ragumani Sugadev contributed to the statistical analysis and data interpretation of the study. The experiments were conducted with help from Manoj Kumar Patel, Shardulya Shukla, and Bhupinder Kaur. All authors have read and approved the final version of the manuscript.
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This study was approved by “Institutional Ethics Committee of Panjab University (PUIEC, Chandigarh)”, (approval no: PUIEC210312-II-044).
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Kumar, N., Kaur, B., Shukla, S. et al. Dietary nitrate supplementation influences the oral denitrifying microbiome in human volunteers: a pilot study. Biologia 79, 2165–2177 (2024). https://doi.org/10.1007/s11756-024-01681-x
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DOI: https://doi.org/10.1007/s11756-024-01681-x