Response of bacteria to soil contamination with heavy metals

The effect of contamination of loamy sand with single heavy metals (Cd2+, Cu2+, Zn2+, Pb2+) and with their mixtures on the number of copiotrophic, ammonifying, nitrogen immobilising, cellulolytic bacteria and bacteria of the Arthrobacter and Pseudomonas genera was examined in a pot experiment. The research was performed in two series: with soil sown with oat and unsown soil. It was found that the sensitivity of bacteria to Cd2+, Cu2+, Zn2+ and Pb2+ is a specific characteristic related to the content of these metals in soil and to the method of soil use. The development of the bacteria of Arthrobacter and Pseudomonas was most strongly inhibited in the soil sown with oat, while ammonifying, nitrogen immobilising, and cellulolytic bacteria were most inhibited in the unsown soil. Copiotrophic, cellulolytic, nitrogen immobilising and ammonifying bacteria proved to be more resistant to this contamination than bacteria of Arthrobacter and Pseudomonas genera. Increasing the number of heavy metals simultaneously contaminating the soil to two (Cd2+ and Cu2+; Cd2+ and Zn2+; Cd2+ and Pb2+) and to three (Cd2+, Cu2+ and Zn2+; Cd2+, Cu2+, and Pb2+; Cd2+, Pb2+ and Zn2+) generally did not increase the intensity of their effect on the examined bacteria. Changes brought about by these mixtures were usually similar to changes caused by individual heavy metals.