Streptococcus sanguinis is primarily associated with oral health as a commensal bacterium. As an opportunistic pathogen, S. sanguinis is capable of colonizing heart valve vegetations, leading to the disease infective endocarditis. Previous studies from our lab have identified the high-affinity manganese transporter SsaACB as important for endocarditis virulence. The impact that manganese depletion has on S. sanguinis had never been evaluated and a secondary manganese transporter has not been identified. Thus, we employed the use of a fermentor to control large-scale growth over time and depleted manganese in an ΔssaACB mutant using a metal chelator, EDTA. The changes in the transcriptome and metabolome of these cells were measured and it was demonstrated that multiple systems were affected. Many of these systems were linked to carbon catabolite repression through CcpA. We found that levels of the glycolytic metabolite fructose-1,6-bisphosphate, a mediator of CcpA-dependent repression, were increased in manganese-depleted cells despite no change in glucose levels. We also evaluated the impact of low pH on the ΔssaACB mutant and found that growth was reduced at pH 6.2. The same pH did not affect the growth of the wild-type SK36 strain. Analysis of both strains in fermentor-grown cultures revealed that reducing the pH affected the manganese levels of cells and again influenced the transcription of multiple systems. Finally, we identified and characterized the secondary manganese transporter, here named TmpA. Here we report that TmpA transports manganese and contributes to endocarditis virulence in several strains of S. sanguinis. We confirmed that manganese is critical for growth and virulence of S. sanguinis and is intricately tied to many systems through its impact on glycolysis. These findings lay the groundwork for future drug development studies targeting either one or both manganese transporters to prevent endocarditis caused by S. sanguinis and related species
