Role of Bipyridinium Salts in Generation of Photocurrent by Rhodospirillum rubrum Cells

Abstract

Abstract An anodic photocurrent was generated when an SnO2 electrode, which was immersed in a culture medium of a photosynthetic bacterium, Rhodospirillum rubrum, or in a buffer suspending the cell body, was illuminated under potentiostatic conditions. The anodic photocurrent was enhanced about four times with addition of methyl viologen (MV) to the cell suspension, but was suppressed with addition of 1,1′-ethylene-2,2′-bipyridinium dibromide (EBP). On the other hand, it was observed spectrophotometrically that EBP was reduced by Rs. rubrum cells about ten times faster than MV. The disagreement in both data of photocurrent and of reduction rate suggests this to be due to the difference of penetrability of the salts through the cell wall and membrane. This suggestion was confirmed from cyclic voltammetric results of the reagents dissolved in the cell suspension.