The Microbial Generation of Nitric Oxide in the Human Oral Cavity

Smith, Narelle B.

doi:10.1080/089106099435880

Cited by 11 publications

(3 citation statements)

References 19 publications

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“…The overall oral bacterial composition was consistent with previous literature, where Firmicutes, Actinobacteria, Bacteroidetes, Proteobacteria and Fusobacteria were the most abundant phyla [ 25 , 26 ]. This is further reflected at the family and genus levels, with Streptococcus , Prevotella , Neisseria and Haemophilus being most abundant genera [ 1 , 15 , 16 , 26 ].…”

Section: Discussionsupporting

confidence: 90%

Localisation of nitrate-reducing and highly abundant microbial communities in the oral cavity

L’Heureux,

van der Giezen,

Winyard

et al. 2023

PLoS ONE

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The nitrate (NO3-) reducing bacteria resident in the oral cavity have been implicated as key mediators of nitric oxide (NO) homeostasis and human health. NO3--reducing oral bacteria reduce inorganic dietary NO3- to nitrite (NO2-) via the NO3--NO2--NO pathway. Studies of oral NO3--reducing bacteria have typically sampled from either the tongue surface or saliva. The aim of this study was to assess whether other areas in the mouth could contain a physiologically relevant abundance of NO3- reducing bacteria, which may be important for sampling in clinical studies. The bacterial composition of seven oral sample types from 300 individuals were compared using a meta-analysis of the Human Microbiome Project data. This analysis revealed significant differences in the proportions of 20 well-established oral bacteria and highly abundant NO3--reducing bacteria across each oral site. The genera included Actinomyces, Brevibacillus, Campylobacter, Capnocytophaga, Corynebacterium, Eikenella, Fusobacterium, Granulicatella, Haemophilus, Leptotrichia, Microbacterium, Neisseria, Porphyromonas, Prevotella, Propionibacterium, Rothia, Selenomonas, Staphylococcus, Streptococcus and Veillonella. The highest proportion of NO3--reducing bacteria was observed in saliva, where eight of the bacterial genera were found in higher proportion than on the tongue dorsum, whilst the lowest proportions were found in the hard oral surfaces. Saliva also demonstrated higher intra-individual variability and bacterial diversity. This study provides new information on where samples should be taken in the oral cavity to assess the abundance of NO3--reducing bacteria. Taking saliva samples may benefit physiological studies, as saliva contained the highest abundance of NO3- reducing bacteria and is less invasive than other sampling methods. These results inform future studies coupling oral NO3--reducing bacteria research with physiological outcomes affecting human health.

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Section: Discussionsupporting

confidence: 90%

Localisation of nitrate-reducing and highly abundant microbial communities in the oral cavity

L’Heureux,

van der Giezen,

Winyard

et al. 2023

PLoS ONE

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“…The only genera of bacteria where the abundance changed significantly was Peptostreptoccocus which was more abundant in visit one compared to visit two (P=0.03). Previous research has shown that Peptostreptoccocus species do not have NO 3 reductase activity (Smith et al 1999).…”

Section: Abundance Of Nitrate-reducing Bacteriamentioning

confidence: 99%

Variability in nitrate-reducing oral bacteria and nitric oxide metabolites in biological fluids following dietary nitrate administration: An assessment of the critical difference

et al. 2019

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There is conflicting evidence on whether dietary nitrate supplementation can improve exercise performance. This may arise from the complex nature of nitric oxide (NO) metabolism which causes substantial inter-individual variability, within-person biological variation (CV B ), and analytical imprecision (CV A ) in experimental endpoints. However, no study has quantified the CV A and CV B of NO metabolites or the factors that influence their production. These data are important to calculate the critical difference (CD), defined as the smallest difference between sequential measurements required to signify a true change. The main aim of the study was to evaluate the CV B , CV A, and CD for markers of NO availability (nitrate and nitrite) in plasma and saliva before and after the ingestion of nitrate-rich beetroot juice (BR). We also assessed the CV B of nitrate-reducing bacteria from the dorsal surface of the tongue. It was hypothesised that there would be substantial CV B in markers of NO availability and the abundance of nitrate-reducing bacteria. Ten healthy male participants (age 25 ± 5 years) completed three identical trials at least 6 days apart. Blood and saliva were collected before and after (2, 2.5 and 3 h) ingestion of 140 ml of BR (~12.4 mmol nitrate) and analysed for [nitrate] and [nitrite]. The tongue was scraped and the abundance of nitratereducing bacterial species were analysed using 16S rRNA next generation sequencing. There was substantial CV B for baseline concentrations of plasma (nitrate 11.9%, nitrite 9.0%) and salivary (nitrate 15.3%, nitrite 32.5%) NO markers. Following BR ingestion, the CV B for nitrate (plasma 3.8%, saliva 12.0%) and salivary nitrite (24.5%) were lower than baseline, but higher for plasma nitrite (18.6%). The CD thresholds that need to be exceeded to ensure a meaningful change from baseline are 25, 19, 37, and 87% for plasma nitrate, plasma nitrite, salivary nitrate, and salivary nitrite, respectively. The CV B for selected nitrate-reducing bacteria detected were: Prevotella melaninogenica (37%), Veillonella dispar (35%), Haemophilus parainfluenzae (79%), Neisseria subflava (70%), Veillonella parvula (43%), 3Rothia mucilaginosa (60%), and Rothia dentocariosa (132%). There is profound CV B in the abundance of nitrate-reducing bacteria on the tongue and the concentration of NO markers in human saliva and plasma. Where these parameters are of interest following experimental intervention, the CD values presented in this study will allow researchers to interpret the meaningfulness of the magnitude of the change from baseline.

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“…In an early study, the estimated excretion of saliva by cattle during feed intake and remastication was between 98 and 190 L d -1 with four different diets (Bailey, 1961). Excretion of NO 3 via saliva could lead to intimate contact between dissolved NO 3 and degradable organic matter in the oral cavity where there is probably also a potential for inoculation with denitrifying organisms (Smith et al, 1999). Further research is needed to identify the mechanism and location of N 2 O formation.…”

Section: Mechanisms Behind Nitrous Oxide Emissionsmentioning

confidence: 99%

Dietary Nitrate for Methane Mitigation Leads to Nitrous Oxide Emissions from Dairy Cows

et al. 2015

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Nitrate supplements to cattle diets can reduce enteric CH emissions. However, if NO metabolism stimulates NO emissions, the effectiveness of dietary NO for CH mitigation will be reduced. We quantified NO emissions as part of a dairy cow feeding experiment in which urea was substituted in nearly iso-N diets with 0, 5, 14 or 21 g NO kg dry matter (DM). The feeding experiment was a Latin square with repetition of Period 1. Each period lasted 4 wk, with CH emission measurements in Week 4 using respiration chambers. During Period 3, NO concentrations in chamber outlet air were monitored semicontinuously during 48 h. High, but fluctuating, NO concentrations were seen at the two highest NO levels (up to between 2 and 5 μL L), and dynamics were linked with recent feed intake. In Periods 4 and 5, NO concentrations and feed intake were determined from all four respiration chambers during two 7-h periods. Emissions of NO coincided with feed intake, again with NO concentrations in the microliter per liter range at the two highest NO intake levels. Neither feed nor excretion of NO via urine were significant sources of NO, indicating that emissions came from the animals. Leakages due to rumen fistulation could also not account for NO emissions. The possibility that NO is produced in the oral cavity is discussed. Nitrous oxide emission factors ranged between 0.7 and 1.0% except in one case at 21 g NO kg DM, where it was 3.4%. When accounting for NO emissions at the highest NO intake level, the overall GHG mitigation effect in two different animal-diet combinations changed from -47 to -40%, and from -19 to -17%, respectively, due to NO emissions.

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The Microbial Generation of Nitric Oxide in the Human Oral Cavity

Cited by 11 publications

References 19 publications

Localisation of nitrate-reducing and highly abundant microbial communities in the oral cavity

Localisation of nitrate-reducing and highly abundant microbial communities in the oral cavity

Variability in nitrate-reducing oral bacteria and nitric oxide metabolites in biological fluids following dietary nitrate administration: An assessment of the critical difference

Dietary Nitrate for Methane Mitigation Leads to Nitrous Oxide Emissions from Dairy Cows

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