Acetylene reduction (nitrogen fixation) by pulp and paper mill effluents and by Klebsiella isolated from effluents and environmental situations.

High rates of acetylene (C(2)H(2)) reduction (nitrogenase activity) were observed in woodroom effluent from a neutral sulfite semi-chemical mill under aerobic (up to 644 nmol of C(2)H(4) produced per ml per h) and under anaerobic (up to 135 nmol of C(2)H(4) produced per ml per h) conditions. Pasteurized effluent developed C(2)H(2) reduction activity when incubated under anaerobic but not under aerobic conditions. Activities were increased by addition of 0.5 to 3.0% glucose or xylose. Enrichment and enumeration studies showed that N(2)-fixing Azotobacter and Klebsiella were abundant, and N(2)-fixing Bacillus was present. Of 129 isolates of Klebsiella from pulp mills, lakes, rivers, and drainage and sewage systems, 32% possessed nitrogen-fixing ability.