ISOLATION OF GENOMIC DNA FROM THE EARTHWORM SPECIES EISENIA-FETIDA

Our interest in detecting genotoxic exposure in earthworms led us to i solate high quality DNA from the Eisenia fetida species. For that, we compared a modification of the conventional phenol-chloroform extracti on procedure, usually refered to as the Maniatis procedure, to two com mercially available kits reportedly eliminating multiple partitions in phenol and chloroform, namely the Qiagen and Nucleon protocols. From the 260 nm optical density values, the commercial kits extracts hinted toward higher DNA recovery with those procedures. However, the 260/28 0 nm ratios indicated that the quality of the DNA isolated with the mo dified Maniatis procedure was purer than that isolated with the commer cial kits, the latter being most probably contaminated by proteins and /or RNA. The Maniatis procedure was slightly modified by the introduct ion of a potassium acetate step for protein precipitation and by short ening the proteinase K treatment from 12-18 h to only 2 h. The higher quality of the DNA isolated by phenol-chloroform extraction was confir med by quantification with the fluorescent 3,5-diaminobenzoic acid ass ay. Preliminary results suggest that the modified Maniatis procedure h erein described is not only applicable for DNA adducts studies using P -32-postlabelling techniques but is also suitable for DNA extraction f rom other earthworm species such as Lumbricus terrestris.