Fig. 6.

B. fragilis Δoxe strain scavenges H₂O₂ at a faster rate than WT. Strains were grown to log phase in AMM (with or without erythromycin), and cells were pelleted by centrifugation. Pellets were resuspended in AMM lacking cysteine and shaken at 37 °C under room air for 1 h. Cells were again pelleted, washed with PBS solution, and resuspended to an OD₆₀₀ of 0.3 in PBS solution containing thymine and 0.5% glucose. H₂O₂ (5 μM) was added to start the assay. Samples were removed over time and centrifuged briefly, and supernatants were assayed for [H₂O₂] by using Amplex Red. Rates are reported in nM H₂O₂ scavenged per minute. Shown are the means of at least three experiments ± SEM. ANOVA revealed a P value of 0.0066. Values for strains marked “a” differed significantly from those marked “b” with a P < 0.05 in a Newman–Keuls multiple comparison posttest.