The Role of Hydrogen Peroxide in Environmental Adaptation of Oral Microbial Communities

Abstract

Oral streptococci are able to produce growth-inhibiting amounts of hydrogen peroxide (H₂O₂) as byproduct of aerobic metabolism. Several recent studies showed that the produced H₂O₂is not a simple byproduct of metabolism but functions in several aspects of oral bacterial biofilm ecology. First, the release of DNA from cells is closely associated to the production of H₂O₂inStreptococcus sanguinisandStreptococcus gordonii. Extracellular DNA is crucial for biofilm development and stabilization and can also serve as source for horizontal gene transfer between oral streptococci. Second, due to the growth inhibiting nature of H₂O₂, H₂O₂compatible species associate with the producers. H₂O₂production therefore might help in structuring the initial biofilm development. On the other hand, the oral environment harbors salivary peroxidases that are potent in H₂O₂scavenging. Therefore, the effects of biofilm intrinsic H₂O₂production might be locally confined. However, taking into account that 80% of initial oral biofilm constituents are streptococci, the influence of H₂O₂on biofilm development and environmental adaptation might be under appreciated in current research.