Effects of salinity on acetylene reduction (nitrogen fixation) and respiration in a marine azotobacter.

An acetylene-reducing (nitrogen-fixing) bacterium, identified as Azotobacter sp., was isolated from a site in the Canary Creek Marsh, Del. Acetylene reduction activity of the isolate was maximal at 15 to 25 per thousand NaCl, with no activity observed at 0 or 60 per thousand. Respiration studies showed similar results, with maximal activity occurring at a slightly lower salinity (10 to 20 per thousand NaCl). The salinities over which peak activity occurred fell within the normal range of in situ salinity (20 to 28 per thousand total salinity).