FIG. 6.

Effect of various growth conditions on adcR expression. The β-galactosidase activities of the adcR-lacZ transcriptional fusion in the biofilm-defective S. gordonii adcR::Tn917-lac mutant are shown. Cultures were grown at 37°C under anaerobic conditions unless specified otherwise. The growth conditions examined were THBYE, BHI, and THBYE containing the following: whole saliva, human serum, Zn, Mn, and various amino acids. Cells were also grown in THBYE at 30 and 42°C and under aerobic conditions at 37°C. The β-galactosidase activities of sonic extracts from each of the cultures were quantified by using MUG (28). All assays were performed in triplicate, and mean values and standard deviations are shown.