Options
1982
Book Article
Titel
Organic acid utilization, succinate excretion and encystation during biphasic nitrogenase activity in azospirillum brasilense under microaerobic conditions
Abstract
Biphasic nitrogenase activity in long lasting batch cultures of Azospirillum brasilense Sp 7 ATCC 29145 is independent of the carbon source malate. With fumarate, succinate or pyruvate as sole carbon source nitrogenase activity is also biphasic. Citrate, however, allows the cells only to develop one phase of nitrogenase activity not earlier than 220 h of incubation. Cultivation in a medium with 20 times the buffer concentration does not effect biphasic nitrogenase activity. Nitrogen fixing cultures of Azospirillum brasilense Sp 7 ATCC 29145 excrete ammonia into the culture medium, varying between 0.02 and 0.04 mM concentrations. This is not sufficient to cause a drop of nitrogenase activity in Azospirillum brasilense after the first maximum. During growth under nitrogen fixing conditions with malate as carbon source, the cells excrete significant amounts of succinate into the culture medium. Cultures with only 0.05% malate reutilized the excreted succinate as soon as malate disappeared from the medium. Azospirillum brasilense ATCC 29145 is shown to have the capability of encystation. (IFU)