Variations of Nitrate-reducing Activity in Oral Rothia mucilaginosa

Abstract

It is well-known that nitric oxide resulting from the reduction of salivary nitrate plays a beneficial antimicrobial role in the oral cavity. Recent genomic analysis of nitrate reductase-positive bacteria in the oral cavity revealed that certain bacterial species (members of Veillonella, Actinomyces, Rothia, Staphylococcus, Corynebacterium, etc.) have the capacity to reduce nitrate. One such species that was notable for its high reducing activity was Rothia mucilaginosa. Recent metagenomics studies have shown a strong correlation between the presence of oral Rothia spp. within oral subgingival bacterial communities and periodontal health. We hypothesize that this correlation results partly from the microbicidal efficacy of the nitrate-reducing system in Rothia. In this study, we evaluated the nitrate reduction abilities of three R. mucilaginosa strains individually using a chromogenic substrate method based on the Griess reaction and a NOx analyzer. We found that, intriguingly, the three strains exhibited different levels of nitrate-reducing activity. This is the first study to reveal the variation in nitrate-reducing capacity among individual oral R. mucilaginosa strains.