Abstract
Pseudomonas spp., Micrococcus spp. and Fusarium oxysporum promote growth and nitrogenase activity in Anabaena cylindrica. Respiratory CO2 production by the microbial associate appears to be the main benefit to the cyanobacterium. Some stimulation of nitrogenase, however, appears to be due to other causes in associations with Pseudomonas and Fusarium.