Abstract
The pyruvate oxidase (SpxB)-dependent production of H(2)O(2) is widely distributed among oral commensal streptococci. Several studies confirmed the ability of H(2)O(2) to antagonize susceptible oral bacterial species, including caries-associated Streptococcus mutans as well as several periodontal pathobionts. Here we report a potential mechanism to bolster oral commensal streptococcal H(2)O(2) production by magnesium (Mg(2+)) supplementation. Magnesium is a cofactor for SpxB catalytic activity, and supplementation increases the production of H(2)O(2) in vitro. We demonstrate that Mg(2+) affects spxB transcription and SpxB abundance in Streptococcus sanguinis and Streptococcus gordonii. The competitiveness of low-passage commensal streptococcal clinical isolates is positively influenced in antagonism assays against S. mutans. In growth conditions normally selective for S. mutans, Mg(2+) supplementation is able to increase the abundance of S. sanguinis in dual-species biofilms. Using an in vivo biophotonic imaging platform, we further demonstrate that dietary Mg(2+) supplementation significantly improves S. gordonii oral colonization in mice. In summary, our results support a role for Mg(2+) supplementation as a potential prebiotic to promote establishment of oral health-associated commensal streptococci.