Temperature-Dependent Regulation by Molybdenum and Vanadium of Expression of the Structural Genes Encoding Three Nitrogenases in Azotobacter vinelandii.

Temperature affects the expression of the three different nitrogenases in Azotobacter vinelandii. Molybdenum repressed the vnfH and anfH operons relatively more at 30 degrees C than at 20 degrees C; at 14 degrees C molybdenum did not repress these genes at all. Similarly, V repressed the anf operon at 30 degrees C but not at 20 or 14 degrees C. Mo was poorly transported into cells grown at the lower temperatures. A. vinelandii thus has the potential to synthesize any of the three nitrogenases at 14 to 20 degrees C regardless of the presence of Mo or V.