FIG. 1.

Response of K. pneumoniae strains to exogenous ammonium. Strains UN5482 (wild type transformed with pCH1, containing draTGB) (■), UN5483 (draTG′) (▴), and UN5491 (vector-only control) (□) were derepressed for nitrogenase activity. After 5 h of derepression, 0.5 mM ammonium acetate was added to each culture (time = 0). The nitrogenase activities of each culture were monitored by the acetylene reduction method at the time points indicated, after the addition of ammonium acetate. Results are expressed as nanomoles of ethylene produced per milliliter of culture per hour.