Changes in culturable bacterial community of soil treated with high dosages of Cu or Cd

Abstract

Culturable bacteria numbers, kinetics of colony formation, community structure analyses in terms of ecological (r/K-strategists) and cytochemical approaches were used to assess the bacteria responses to soil treatment with high concentrations of Cu or Cd over time. The soil treatment resulted in high concentrations of water-soluble forms of the metals. Bacterial numbers significantly decreased in the metal-treated soil shortly after the soil contamination, their numbers however increased during incubation time. The short- or long-term contact of bacteria with the metals significantly decreased or increased the rate of cell proliferations, respectively. The populations represented by slow-growing K-strategists dominated the structures of bacterial communities with time. The results of fatty acid methyl ester analyses indicated that Gram-positive bacteria dominated shortly after soil contamination; however, changes in the community structures with stimulation of Pseudomonas in the Cd-treated soil occurred after prolonged exposure to the metal. This study shows that short- or long-term exposition to heavy metals may cause different quantitative and qualitative effects on culturable bacteria in soil.