Creatinine inhibits bacterial replication (a–f) potentially by overwhelming the bacterial cells ability to pump out protons (d–i). MIC measurements for CRN-HCl against E. coli and S. aureus determined in shaking tube culture (a) or stationary 96-well microtiter dish formats (E. coli (b); S. aureus (c)). The MICs for the two bacterial species were the same regardless of the format employed. Arrows indicate MIC as well as the first tube or well in the series that was not visibly turbid. Replication of bacteria derived from samples of (d) human feces or (e) garden soil was suppressed in the presence of 100 mM CRN-HCl. Left hand plate in each panel contains no CRN-HCl; right hand plates contain 100 mM CRN-HCl. Example of fungal growth following 10 days of incubation at room temperature on an LBG agar plate containing 100 mM CRN-HCl (c). The synergy between the inhibitory action of CRN-HCl and the action of the proton efflux inhibitor CCCP in lowering the concentration of CRN-HCl necessary for growth inhibition is demonstrated for E. coli (g), S. aureus (h) and B. subtilis (i). In the presence of CCCP, the MICs are left shifted. Arrows indicate the MIC at which neither detectable turbidity was observed by the eye nor OD when measured at 600 nm.