Fig. 3.

Effect of an electron donor and accepter in the generation of semiquinone (Sq) free radical in MR-1 cells. Electron spin resonance difference spectrum obtained at 77 K for suspension of S. oneidensis MR-1 cells in the presence of 16 μM FMN and 5 mM lactate as an electron donor (A) with and (B) without added Fe₂O₃ particles as an electron acceptor. For (C), lactate was not added into the cell suspension. For all measurements, cell suspensions in 50% glycerol were prepared under anaerobic conditions. The spectrum of the cell suspension with 50% (vol/vol) glycerol was used as reference.