Fig. 1. Genotype of luciferase reporter strains.
A markerless mutagenesis approach was used to construct the respective luciferase fusions for S. mutans. S. sanguinis and S. gordonii reporters were constructed using an erythromycin resistance cassette (erm) for the selection of mutant clones. The luciferase open reading frames (ORF) were all cloned immediately downstream of the ldh stop codons to create artificial two-gene operons. Each luciferase cassette contained a copy of the ldh Shine-Dalgarno sequence to ensure its efficient translation.