Fig 2. Phase II genes are upregulated in response to H₂O₂ produced by the mitis group streptococci.

(A) qRT-PCR analysis of Phase II genes gst-4 and gcs-1 induced in worms fed for 2 hours on S. gordonii WT and ΔspxB mutant strains. Experiments were performed with three separate replicates; each replicate was measured in duplicate and standardized to the control gene act-1. Error bars represent the standard error of the mean (SEM), P<0.001. (B) Representative images of gcs-1::gfp expression in worms exposed to WT, ΔspxB mutant and ΔspxB;spxB⁺ complemented strains of S. gordonii for 2 hours. (C) The level of gcs-1::gfp expression and the percentage of worms in each category fed on WT, ΔspxB mutant and ΔspxB;spxB⁺ complemented strains of S. gordonii. A total of more than 100 worms exposed to each strain were imaged and the experiment was repeated 3 times. Significantly low levels of gcs-1::gfp expression was observed in the ΔspxB mutant (P<0.0001) compared to the WT and ΔspxB;spxB⁺ complement strains of S. gordonii.