MATERlALS AND METHODS
Microorganism and culture medium A denitrifying photosynthetic bacterium, R. sphaeroides S (7, 8) was used in this study. Stock culture was maintained as described previously (11).
Glutamate malate (GM) medium (11) which contained 5 g/l of KN03 was used for denitrifying growth of this strain. GM medium without KN03 was used for precultivation medium.