Pyruvate can enter the TCA cycle and serve as a key metabolite for the microbes to maintain normal physiological functions . Wang et al. found that hexavalent chromium exposure suppressed pyruvate metabolism in Shewanella oneidensis . In agreement with this finding, we also found that MSNs significantly affected the pyruvate metabolism, suggesting that MSNs might hamper the normal functions of E. coli by disturbing this important metabolite.