Effect of glucose concentrations on the expression of cit operons, CitO levels and citrate lyase activity. A and B) JHB2 (JH2-2/pTCV-PcitHO), JHB6 (JH2-2/pTCV-PcitCL), CL1 (CL14/pTCV-PcitHO) and CL2 strains (CL14/pTCV-PcitCL) were grown in LBC (circle) or LBC supplemented with different initial concentrations of glucose: 0.25% (square), 0.5% (up-pointing triangle) and 1% (down-pointing triangle). The corresponding open symbols indicate the remaining glucose concentration in the culture medium (right axis). Levels of accumulated β-galactosidase activity were measured at different times as indicated in the figure. C and D) E. faecalis strains were grown in the same conditions of panels A and B, and cells extracts were obtained 7 h after inoculation, C) Western blot analysis was performed with polyclonal antibodies raised against CitO. D) Citrate lyase activity was determined as described previously . Error bars represent standard deviation of triplicate measurements.