Nitrate and the Origin of Saliva Influence Composition and Short Chain Fatty Acid Production of Oral Microcosms

Abstract

Nitrate is emerging as a possible health benefactor. Especially the microbial conversion of nitrate to nitrite in the oral cavity and the subsequent conversion to nitric oxide in the stomach are of interest in this regard. Yet, how nitrate influences the composition and biochemistry of the oral ecosystem is not fully understood. To investigate the effect of nitrate on oral ecology, we performed a 4-week experiment using the multiplaque artificial mouth (MAM) biofilm model. This model was inoculated with stimulated saliva of two healthy donors. Half of the microcosms (n = 4) received a constant supply of nitrate, while the other half functioned as control (n = 4). Additionally, all microcosms received a nitrate and sucrose pulse, each week, on separate days to measure nitrate reduction and acid formation. The bacterial composition of the microcosms was determined by 16S rDNA sequencing. The origin of the saliva (i.e., donor) showed to be the strongest determinant for the development of the microcosms. The supplementation of nitrate was related to a relatively high abundance of Neisseria in the microcosms of both donors, while Veillonella was highly abundant in the nitrate-supplemented microcosms of only one of the donors. The lactate concentration after sucrose addition was similarly high in all microcosms, irrespective of treatment or donor, while the concentration of butyrate was lower after nitrate addition in the nitrate-receiving microcosms. In conclusion, nitrate influences the composition and biochemistry of oral microcosms, although the result is strongly dependent on the inoculum.Electronic supplementary materialThe online version of this article (doi:10.1007/s00248-016-0775-z) contains supplementary material, which is available to authorized users.

Increasing dietary nitrate has no effect on cancellous bone loss or fecal microbiome in ovariectomized rats

“…Prior work has demonstrated dietary nitrate can alter oral microbiome composition 63, 64. However, little is known about interaction between dietary nitrate and the gut microbiome.…”

Enterosalivary nitrate metabolism and the microbiome: Intersection of microbial metabolism, nitric oxide and diet in cardiac and pulmonary vascular health

“…[190,200–204]. Using nitrate supplementation as selective pressure for bacteria capable of nitrate reduction, several studies found proliferation of Veillonella [205], Streptococcus [204], Neisseria [115], Haemophilus [204], and Rothia species[115], all previously identified as high nitrate reducers. Yet, despite these varied attempts, there remains a high degree of variability in results depending on numerous methodological factors[206], including source and sampling of sample (saliva versus oral wash versus tongue scraping), direct sampling versus culture, and choice of 16S variable region for sequencing.…”

“…Nitrite can exert pH-dependent antimicrobial effects[204,232,233] via formation of reactive secondary nitrogen oxides that can disrupt aerobic respiration[234], inhibit bacterial acid production, and disrupt biofilm formation[235–237]. In settings of low pH and high nitrate and nitrite concentrations, selected bacteria and bacterial communities capable of nitrate reduction may preferentially survive or expand their population[115,205]. Indeed, increased production of the weak base, ammonia via nitrate reduction is a well-known strategy for bacteria to alkalinize their cytoplasm and local environment and protect against the potential toxic effects of high concentrations of nitrate, nitrite and NO[238].…”

“…Indeed, increased production of the weak base, ammonia via nitrate reduction is a well-known strategy for bacteria to alkalinize their cytoplasm and local environment and protect against the potential toxic effects of high concentrations of nitrate, nitrite and NO[238]. This may relate to the paradoxical association between nitrate-reducing oral bacteria and protection from dental caries[191,205,232,238,239]. …”

Dysbiosis of the Oral Ecosystem in Severe Congenital Neutropenia Patients

“…The reads were processed into OTUs as described previously. [ 19 ] The most abundant sequence of each OTU was classified using the RDP classifier [ 20 ] and HOMD version 14.51. [ 21 ]…”