Heavy metals both these trace elements necessary for life , as well as those niepełniące any physiological functions constitute a serious threat to human and animal health . Human activities has led to the emergence of huge amounts of these metals in soils around the world. Due to the high toxicity of heavy metals , there is an urgent need to develop more efficient and cheaper methods of soil remediation . Conventional methods of soil remediation are inefficient and expensive , and often result in the destruction of natural habitats .

Genetic, biochemical and cytological studies on cytosine methylation in eukaryotic orga-nisms indicate intriguing links between DNA methylation, histone methylation, RNA interference and chroma- tin remodeling. It is clear that no single pathway accounts for all DNA methylations found in Eukaryota. In this article several general mechanisms which control methylation are briefly described.