Nitrogen fixation by anaerobic cellulolytic bacteria.

Four strains of anaerobic nitrogen-fixing, cellulose-fermenting bacteria were isolated in pure culture from freshwater mud and soil. Nitrogenase activity was demonstrated in these strains and also in several previously described anaerobic cellulolytic bacteria isolated from various natural environments. These are the first anaerobic bacteria known to use cellulose as an energy source for nitrogen fixation. Because cellulose is a plant polysaccharide that abounds in nature, these results raise the possibility that nitrogen-fixing, cellulose-fermenting bacteria may be widespread and thus play a major role in carbon and nitrogen cycling.