Combined Effects of Cadmium and Phenanthrene on DNA Sequence Diversity of Soil Microbial Community

Pollution of soil environment has become a se-rious problem in many countries, including China.Heavy metal (HM) and polycyclic aromatic hydro-carbons (PAHs) are two of the most abundant andpotentially harmful pollutants found in most pol-luted soil[1, 2]. Besides their natural occurrence,heavy metals may enter the soil environmentthrough anthropogenic activities, such as mining,smelting, sewage sludge disposal, application ofpesticides and inorganic fertilizers, and atmospher-ic deposition. …

Combined Effects of Cadmium and Phenanthrene on DNA Sequence Diversity of Soil Microbial Community

The DNA sequence diversities for microbial communities in soils contaminated by heavy metal (HM) Cadmium (Cd) and polycyclic aromatic hydrocarbon (PAH) phenanthrene were evaluated by Random Amplified Polymorphic DNA (RAPD) analysis in pot and laboratory experiments. Fourteen random primers were used to amplify RAPDs from microbial community DNAs in four soils contaminated by HM or/and PAH. The products of 14 primers were separated in gel and generated 212 reliable fragments, of which 203 were polymorphic. The numbers of microorganisms (fungi, bacteria and actinomycetes) were also analyzed. The results showed that the total number of microorganisms in the soil polluted by Cd was lowest among the soils, about 67.4 % lower than the soil without pollution, especially the number of bacterial, about 73.8 %. In contrast, there was the highest number of microorganisms in the soil polluted by phenanthrene, about 180 % more than those in the control without pollution, especially the number of actinomycete, about 19 times of control. The number of microorganism of soil polluted by Cd + phenanthrene was fallen between Cd and phenanthrene, about 19.5 % lower than control. The number of fungi showed no significant differences among soils. However, increases in DNA sequence diversity were observed in all contaminated soil samples. The effects were stronger in the case of soil contaminated with PAH and HM than those in soils amended with HM or PAH, separately. The soil with Cd and phenanthrene had the highest richness, modified richness and Shannon-Weaver index. These results showed that HM or/and PAH might result in some changes for soil microbe's DNA itself, such as sequence breakage or insertion and genomic rearrangement. The RAPD marker technique combined with traditional methods appears to be an effective approach for studying the combined effects of HM and PAH on DNA sequence diversity of soil microbial community.