Nitrite Production from Nitrate and Its Link with Lactate Metabolism in Oral spp.

species are among the major anaerobes in the oral cavity and are frequently detected in both caries lesions and healthy oral microbiomes. They possess the ability to utilize lactate and convert nitrate (NO) into nitrite (NO). Recently, interest in NO has increased rapidly because of its beneficial effects on oral and general health; i.e., it inhibits the growth and metabolism of oral pathogenic bacteria, such as , and lowers systemic blood pressure. However, there is only limited information about the biochemical characteristics of NO production by species. We found that NO did not inhibit the growth of or , and it inhibited the growth of only at a high concentration (100 mM). However, NO inhibited the growth of at a low concentration (0.5 mM), while a higher concentration of NO (20 mM) was needed to inhibit the growth of species. NO production by species was increased by environmental factors (lactate, acidic pH, and anaerobic conditions) and growth conditions (the presence of NO or NO) and was linked to anaerobic lactate metabolism. A stoichiometric evaluation revealed that NO is reduced to NO by accepting reducing power derived from the oxidization of lactate. These findings suggest that the biochemical characteristics of NO production from NO and its linkage with lactate metabolism in oral species may play a key role in maintaining good oral and general health. The prevalence of dental caries is still high around the world. Dental caries is initiated when the teeth are exposed to acid, such as lactic acid, produced via carbohydrate metabolism by acidogenic microorganisms. species, which are among the major oral microorganisms, are considered to be beneficial bacteria due to their ability to convert lactic acid to weaker acids and to produce NO from NO, which is thought to be good for both oral and general health. Therefore, it is clear that there is a need to elucidate the biochemical characteristics of NO production in species. The significance of our research is that we have found that lactate metabolism is linked to NO production by species in the environment found in the oral cavity. This study suggests that species are potential candidates for maintaining oral and general health.