Talk: Bob Rosier ‘The benefits of nitrate reduction by the oral microbiota’
Bob Rosier, PhD-candidate in the group of Dr. Alex Mira ( The Human Microbiome Laboratory), Center for Advanced Research in Public Health, FISABIO Foundation (Valencia) recently gave a talk during his virtual visit to the CRC 1182 at Kiel University:
“From improved sport performance to dental caries prevention – the benefits of nitrate reduction by the oral microbiota.”
Salivary glands concentrate plasma nitrate into saliva, leading to high nitrate concentrations that can reach 5-8 mM after a nitrate-rich vegetable meal. Whereas human cells cannot reduce nitrate to nitrite effectively, certain oral bacteria can. This leads to an increase in systemic nitrite that can increase sport performance and improve conditions such as hypertension and diabetes through nitric oxide availability. Nitrate is also an ecological factor that can induce rapid changes in structure and function of polymicrobial communities, but the effects on the oral microbiota have not been clarified. To test this, an in vitro study was set up to determine the effect of nitrate on oral communities grown from saliva of 12 healthy individuals. In a second study, 53 nitrate-reducing isolates were obtained and the effect of six probiotic candidates from the genus Rothia was tested in the same in vitro model. Finally, we studied the effects of nitrate-rich beetroot extracts on oral acidification after sugar rinsing in 24 individuals. Supernatants or saliva samples were taken for nitrate, nitrite, ammonium, lactate and pH measurements. Additionally, the bacterial composition of in vitro biofilms and salivary pellets were determined using 16S rRNA gene Illumina sequencing. We showed that nitrate stimulates the growth of the beneficial genera Rothia and Neisseria in our in vitro model, while potentially decreasing caries-, halitosis- and periodontal disease-associated bacteria. Additionally, nitrate limited or prevented lactic acid (organic acid involved in caries development) accumulation and pH drops during sugar fermentation by the oral microbiota. A selection of Rothia isolates further increased lactate usage and nitrate reduction capacities of oral communities, being of potential benefit for dental health and systemic health, respectively. We propose that nitrate could be used as a prebiotic and nitrate reducing isolates as potential probiotics to treat or prevent oral dysbiosis and improve general oral health.