Influence of soil properties on the development of bacterial community tolerance to Cu, Ni, Pb and Zn

Pollution-Induced Community Tolerance (PICT) is a helpful and sensitive methodology to evaluate the effect of metal pollution in soils using microorganisms as indicators. PICT was used to determine the increase of bacterial community tolerance to Cu, Ni, Pb and Zn (Delta log IC50), and to assess the influence of soil properties on the development of bacterial community tolerance to Cu, Ni, Pb, and Zn. Soil samples showed a wide range of properties, such as pH (3.96-7.47), texture (13.8-31.7% clay) or organic matter (9.7-30.7%). Bacterial growth measured by the [3H]-leucine incorporation method was used as the PICT endpoint. Bacterial communities generally developed tolerance in response to Cu, Ni and Zn additions to soils. However, bacterial communities showed no tolerance to Pb, probably due to high Pb sorption in studied soils. Soil properties influenced the development of bacterial community tolerance to Cu, Ni and Zn. Effective cation exchange and a soil sorption parameter (Freundlich's linearity index) were the selected variables to estimate Delta log IC50 to Cu (R2 = 0.65). Clay content and Ni-soluble are the main factors to estimate Delta log IC50 to Ni (R2 = 0.63). Organic matter content and a sorption parameter (maximum sorption capacity of the soil from Langmuir equation) are the soil properties to estimate Delta log IC50 to Zn (R2 = 0.45). Most of the variables exerted their effect in soil, i.e. PICT selection phase. However, clay content affected bacterial community tolerance determination (PICT detection phase), leading to overestimated measurements of bacterial community tolerance.

Automated summary

Pollution-Induced Community Tolerance (PICT) is a useful methodology to evaluate the effect of metal pollution in soils using microorganisms as indicators. Soil properties influence the development of bacterial community tolerance to different metals.