Fig. 9. B. thetaiotaomicron cells generate endogenous H₂O₂ at a faster rate than does E. coli.

Exponentially growing non-scavenging (“Hpx⁻”) mutants of B. thetaiotaomicron (ΔkatE ΔahpC Δrbr1 Δrbr2) and E. coli (ΔkatG ΔkatE ΔahpCF) were grown in anoxic BHIS or LB, respectively, to exponential phase. They were then washed and suspended in aerated PBS/glucose, and H₂O₂ accumulation in the growth medium was monitored. No detectable H₂O₂ accumulated either in sterile PBS/glucose or in cultures containing either wild-type organism.