DNA extraction from activated sludges

To optimize the cell lysis step for DNA extraction from activated sludge sa mples, two flee dispersion methods (sonication versus stirring with a catio n exchange resin), and three cell lysis treatments (lysozyme + SDS, sonicat ion in a water bath, and thermal shock) were tested. For dispersion, stirri ng with cation exchange resin was more efficient than sonication. The cell lysis procedures were applied in two sequences, and DNA was quantified afte r each cell lysis treatment. Lysozyme + SDS was the most effective step in the cell lysis procedures. The cell lysis treatment sequences giving the hi ghest DNA yields were not the same for all the sludges. The differences in sludge microbial compositions and flee structures required specifically ada pted cell lysis protocols. The proposed protocols were highly efficient for DNA extraction, yielding about 50 mg DNA g(-1) volatile suspended solids, and allowed PCR amplification of 16S rDNA.