The Adaptation of Rhodopseudomonas sphaeroides f. sp. denitrificans for Growth Under Denitrifying Conditions

SUMMARY: The adaptation of cells of Rhodopseudomonas sphaeroides f. sp. denitrificans for growth under denitrifying conditions in the light has been studied. The presence of nitrate in photosyntheti-cally grown bacterial cultures resulted in a drastic reduction of carotenoid and bacteriochloro-phyll contents as well as a loss of one of the polypeptides of the light harvesting complex, resulting in colour changes. Denitrifying cells had high activities of nitrate, nitrite and nitrous oxide reductases. The polypeptides corresponding to subunits of these enzymes were separated by PAGE. Synthesis of these enzymes was studied by pulse-chase labelling techniques. Nitrate and nitrite reductases are constitutive enzymes and it is likely that copies of mRNA for synthesis of these enzymes are “long lived” in the cells.