Abstract
The reductases of the denitrification pathway of Bacillus stearothermophilus, a thermophilic denitrifier, were surveyed in vitro. Nitrate, nitrite and nitric oxide reductases were found to be membrane‐bound, and nitrite reductase may be a copper‐containing enzyme by virtue of its rapid inactivation by the chelator, diethyldithiocarbamate. Nitric oxide reductase exhibited an optimal rate at about pH 7 rather than 5.0–5.5, as expected from the enzyme utilized by several mesophiles. Nitrous oxide reductase was not detected in assays employing reduced benzyl or methyl viologen, in spite of the appreciable N2O‐uptake activity of intact cells.