Regulation of aerobic hydrogen metabolism in diazotrophic cyanobacteria

Abstract

A comparative study of photosynthesis, nitrogen anti hydrogen metabolism carried out on the cyanobiont of Cycas circinalis coralloid roots and the cultured isolate, Anabaena cycadeae. The cyanobiont showed lower rates of photosynthesis, had a higher heterocyst frequency and nitrogenase activity, and lacked uptake hydrogenasc. Increase in light intensity caused stimulation of photosynthesis and nitrogenase activity of the cultured Anabaena cycadrae but the response in the cyanobiont was far less pronounced. Activities of glutamine synthctase (both biosynthetic and transferase), aspartate dehydrogenase, alanine dehydrogenase and glutamate pyruvatc transaminase, in the cyanobiont, were 30-60% lower than those in its freeliving form Anabaena cycadeae. Glutamate oxaloacetate transaminase, on the other hand, was significantly higher in the cyanobiont. Glutamate dehydrogenase and nitrate reductase were undetectable.