Figure 6

Effect of ROS pretreatment on viability of L. biflexa exposed to lethal concentrations of ROS. WT L. biflexa was pretreated with sub-lethal levels of H₂O₂ (left panel) or superoxide generated by paraquat (right panel) and compared to samples that were not pretreated. Subsequently, cultures were exposed to varying concentrations of ROS and viability assessed by either colony counts on solid medium (H₂O₂) or by enumerating motile spirochetes using a Petroff-Hauser counting chamber and darkfield microscopy (paraquat). UN, untreated cells; PT, pretreated cells. One-way ANOVA was used to determine significant differences between treated and the respective untreated samples (* denotes P value < 0.05, *** denotes P value < 0.0001,). Values represent the mean ± the standard error. + denotes that statistical analysis was not performed because the value was zero and a standard error could not be calculated.