Investigation of heavy metal resistance in some bacterial strains isolated from industrial soils

Soil samples were collected from an industrial area in Kazanlı, Mersin, Turkey. Six heavy metals, Cr, Cu, Ni, Co, Cd, and Zn, were tested. ICP-AES analyses were carried out to detect the heavy metal levels of the soil samples. The analysis of test samples revealed high levels of Ni and Cr. A total of 272 Pseudomonas spp. and 161 Bacillus spp. strains were isolated from soils from 4 different sampling locations. The maximum tolerable metal concentrations (MTCs) of Cr, Cu, Ni, Co, Cd, and Zn for each isolate were determined. Resistance to Cr was found in 73.9% of the bacterial strains isolated from soil samples, whereas 26% of the isolates exhibited resistance to Ni, 18.4% to Zn, 11.5% to Cd, 9.2% to Co, and 7.3% to Cu. Observed maximum MTCs were 5 mM for Zn and Cu, 3 mM for Ni, and 2 mM for Cr. Plasmids of sizes 1.8, 2.1, and 28 kb were detected in most Pseudomonas spp. strains with resistance to Cu, Cr, Zn, and Ni.