title: Lack of carbon substrate repression of uptake hydrogenase activity in Bradyrhizobium japonicum SR.
abstract: The expression of ex planta uptake hydrogenase (Hup) activity in Bradyrhizobium japonicum SR induced in the absence or presence of carbon substrates was compared. Hup activity was influenced by pH, indicating that acidification of induction medium with low buffering capacity resulting from carbon substrate metabolism inhibited Hup activity. Cell suspensions in medium with adequate buffering capacity and carbon substrate were limited in O2; increasing O2 availability to cells during induction stimulated Hup expression. The data showed a lack of carbon substrate repression of Hup activity in cell suspensions provided with adequate O2 and buffering capacity.
authors.affiliation: Nitrogen Fixation and Soybean Genetics Laboratory, U.S. Department of Agriculture, Beltsville, Maryland 20705.
authors.forename: P
authors.initials: P
authors.lastname: van Berkum
authors.forename: R J
authors.initials: RJ
authors.lastname: Maier
mesh_terms: D050260:Carbohydrate Metabolism; D003470:Culture Media; D004790:Enzyme Induction; D004794:Enzyme Repression; D005971:Glutamates / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D010088:Oxidoreductases / Q000096:biosynthesis* / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D012230:Rhizobiaceae / Q000201:enzymology* / Q000378:metabolism; D013386:Succinates / Q000378:metabolism*
chemical_list: D003470:Culture Media; D005971:Glutamates; D013386:Succinates; D010088:Oxidoreductases; C029746:uptake hydrogenase; D010100:Oxygen