The role of extracellular polysaccharide in cell viability and nitrogenase activity of Beijerinckia derxii

Cells of Beijerinckia derxii grown on NH4+ or N2 as the nitrogen source were treated to remove their extracellular polysaccharide layer without loss of viability. An adequate method for extracellular polysaccharide extraction was established. After extracellular polysaccharide removal N2-grown cells showed reduced nitrogenase activity, and when stirred for 90 min at 200 rpm, suffered a total loss of viability. In contrast, NH4+-grown cells were not affected when submitted to the same conditions. However, these cells showed a high sensitivity to saline solution. Key words: extracellular polysaccharide, nitrogenase, Beijerinckia derxii, exopolysaccharide.