[Species and strain sensitivity of diasotrophs to heavy metals].

The species and strain sensitivity of free and symbiotic nitrogen-fixing agents to heavy metals: cadmium, copper, lead and zinc in the gradient of concentration from 0.5 to 20.0 MPC/l has been studied under the laboratory conditions. Azotobacter (35 strains) and rhizobia (63 strains) have been tested. It has been established that zinc and copper are more toxical for free nitrogen-fixing agents than lead and cadmium. Among symbiotrophic nitrogen-fixing agents the nodule bacteria for alfalfa were most sensitive to cadmium; nodule bacteria of pea and lupine--to copper; those of galega and soya--to zinc. Lead proved to be the least toxic for rhizobia. Negative effect of the heavy-metal mix on diasotrophs was higher than that of each separate metal. The cultures resistant to the effect of heavy metals have been found which may be used when producing preparation for biological reclamation of polluted soils.