Magnesium-Dependent Promotion of H <sub>2</sub> O <sub>2</sub> Production Increases Ecological Competitiveness of Oral Commensal Streptococci
Xingqun Cheng, Sylvio Redanz, Puthayalai Treerat, Hua Qin, Dongseok Choi, Xuedong Zhou, Xin Xu, Justin Merritt, Jens Kreth
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.