Copper ions inhibit Streptococcus mutans–Veillonella parvula dual biofilm by activating Streptococcus mutans reactive nitrogen species

AbstractBackgroundTo investigate the inhibition mechanism of copper ions onStreptococcus mutans–Veillonella parvuladual biofilm.MethodsS. mutans–V. parvuladual biofilm was constructed and copper ions were added at different concentrations. After the biofilm was collected, RNA-seq and qRT-PCR were then performed to get gene information.ResultsThe coculture ofS. mutansandV. parvulaformed a significantly better dual biofilm of larger biomass thanS. mutansmono biofilm. And copper ions showed a more significant inhibitory effect onS. mutans–V. parvuladual biofilm than onS. mutansmono biofilm when copper ions concentration reached 100 µM, and copper ions showed a decreased inhibitory effect onS. gordonii–V. parvuladual biofilm andS. sanguis–V.parvuladual biofilm than on the two mono biofilms as the concentration of copper ions increased. And common trace elements such as iron, magnesium, and zinc showed no inhibitory effect difference onS. mutans–V. parvuladual biofilm. The RNA-seq results showed a significant difference in the expression of a new ABC transporterSMU_651c,SMU_652c,SMU_653c, andS. mutanscopper chaperonecopYAZ.SMU_651c,SMU_652c, andSMU_653cwere predicted to function as nitrite/nitrate transporter-related proteins, which suggested the specific inhibition of copper ions onS. mutans–V. parvuladual biofilm may be caused by the activation ofS. mutansreactive nitrogen species.ConclusionsStreptococcus mutansandVeillonella parvulaare symbiotic, forming a dual biofilm of larger biomass to better resist the external antibacterial substances, which may increase the virulence ofS. mutans. While common trace elements such as iron, magnesium, and zinc showed no specific inhibitory effect onS. mutans–V. parvuladual biofilm, copper ion had a unique inhibitory effect onS. mutans–V. parvuladual biofilm which may be caused by activatingS. mutansRNS when copper ions concentration reached 250 µM.