A DIRECT DEMONSTRATION OF CO-RESPIRATION OF OXYGEN AND NITROGEN-OXIDES BY PSEUDOMONAS-NAUTICA - SOME SPECTRAL AND KINETIC-PROPERTIES OF THE RESPIRATORY COMPONENTS

Pseudomonas nautica grown anaerobically is capable of simultaneously utilizing oxygen and nitrate or its reduced products (nitrite and nitrous oxide). Evidence for this 'co-respiration' came from kinetic studies on oxygen consumption depending on oxygen concentration and from spectral studies which revealed changes in the cytochromes composition of the electron transport chain under aerobic or anaerobic conditions. A constitutive o-type cytochrome oxidase was detected either aerobically or anaerobically with an apparent K(m) for O2 evaluated at 315-mu-M. Two oxidases were induced only in anaerobic conditions. One of these two enzymes identified as a cd-type cytochrome oxidase shows a relatively high affinity for oxygen with an apparent K(m) value of 25-mu-M.