Relative gene expression of L. biflexa hemA , hemE , hemL , and hemH genes measured by real-time quantitative RT-PCR. The levels of specific mRNA transcript of hemAELH genes were quantified in wild-type (bars in white), rrlep mutant (bars in grey), and hklep mutant (bars in black) grown in EMJH supplemented with 2 (left bar) or 10 μM (right bar) hemin. The amounts of mRNA transcript are shown relative to the quantity of that particular mRNA transcript in EMJH condition (without hemin). As an endogenous control, the 23S rRNA (23S rRNA = 1.0) was used for normalization of transcript levels. Experiments were performed in triplicate from distinct cultures to establish standard deviations.