Application of the photoacoustic method to the measurement of acetylene reduction by nitrogenase enzyme

Nitrogenase is an enzyme responsible for the reduction of the atmospheric N 2 into NH 4 + , which represents the key entry point of the molecular nitrogen into the biogeochemical cycle of nitrogen. This enzyme is present in the rhizobial bacteroids, which are symbionts in a Leguminosae plant (Acacia Hotosericea), and also reduces acetylene into ethylene at the same rate as the nitrogen reduction. Therefore, a CO 2 Laser Photoacoustic system was used for detecting and monitoring the ethylene emission by the nitrogenase activity, in the rhizobial symbionts in Acacia Holosericea, when they are confined in test tubes with acetylene at two different volumes (0.1 and 0.5 ml). Ethylene concentrations are also determined in the ppm range.