title: Enhancement of specific nitrogenase activity in Azospirillum brasilense and Klebsiella pneumoniae, inhibition in Rhizobium japonicum under air by phenol.
abstract: Specific nitrogenase activity in Azospirillum brasilense ATCC 29145 in surface cultures under air is enhanced from about 50 nmol C2H4 X mg protein -1 X h-1 to 400 nmol C2H4 by the addition of 1 mM phenol. 0.5 and 2 mM phenol added increase the rate 5-fold and 4-fold. This enhancement effect is observed only between 2 and 3 days after inoculation, with only a small reduction of the growth of the cells by the phenol added. In surface cultures under 1% O2, nitrogenase activity is slightly reduced by the addition of 1-0.01 mM phenol. Utilization of succinate is enhanced during the period of maximum enhancement of nitrogenase activity by 60% by addition of 1 mM phenol. The cells did not produce 14CO2 from [U-14C] phenol, neither in surface cultures nor in liquid cultures and less than 0.1% of the phenol was incorporated into the cells. A smaller but significant enhancement of nitrogenase activity by about 100% in surface cultures under air was found with Klebsiella pneumoniae K 11 after addition of 1 mM phenol. However, in Rhizobium japonicum 61-A-101 all phenol concentrations above 0.01 mM reduced nitrogenase activity. With 1 mM phenol added activity was reduced to less than 10% with no effect on the growth in the same cultivation system. With this Rhizobium japonicum strain significant quantities of phenol (25 mumol in 24 h by 2 X 10(12) cells) were metabolized to 14CO2, with phenol as sole carbon source. With Azospirillum brasilense in liquid culture under 1% and 2% O2 in the gas phase, no enhancement of nitrogenase activity by phenol was noticed.
mesh_terms: D001419:Bacteria / Q000187:drug effects / Q000201:enzymology*; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology*; D009591:Nitrogenase / Q000032:analysis*; D019800:Phenol; D010636:Phenols / Q000378:metabolism / Q000494:pharmacology*; D012231:Rhizobium / Q000187:drug effects / Q000201:enzymology*
chemical_list: D010636:Phenols; D019800:Phenol; D009591:Nitrogenase