Variations in Laboratory-Scale Actinomycete Communities Exposed to Cadmium as Assessed by Denaturing Gradient Gel Electrophoresis Profiles

The actinomycete populations and functions in cadmium (Cd) contaminated soil were investigated by the cultivationindependent molecular methods.The genomic DNA was extracted and purified from soil adulterated with various concentrations of Cd in the laboratory.The partial 16S rDNA genes were amplified by polymerase chain reaction (PCR) using specific primers bound to evolutionarily conserved regions within these actinomycete genes.The diversity in PCRamplified products,as measured by denaturing gradient gel electrophoresis (EGGE),was used as a genetic fingerprint of the population.Principle component analysis and Shannon-Weaver diversity index (H) analyses were used to analyze the DGGE results.Results showed that the two principal components accounted for only a low level of the total variance.The value H in contaminated soil was lower than that in the control at later stages of cultivation,whereas at earlier stages it was higher.Among the six sampling time points,the first,fifth and sixth weeks had the highest values of H.Significantly negative correlations between bioavailable Cd concentration and H values existed in the samples from weeks 2 (R=0.929,P < 0.05) and 4 (R=0.909,P < 0.05).These results may shed light on the effect of Cd on the soil environment and the chemical behavior and toxicity of Cd to actinomycetes.