DNA damage caused by common cytological fixatives

Abstract

Tissues from nine species of plants and fungi were treated separately with eight solutions, including seven cytological fixatives (3.7% formaldehyde at pH 3.0 and 7.0, FAA at pH 3.0 and 7.0, 1% glutaraldehyde at pH 3.0 and 7.0, and Lavdowsky's fluid at pH 3.0) and one storage buffer (SED=NaCl–EDTA–DMSO, pH 7.0). DNA from untreated tissue and SED-treated tissue was of high molecular weight (>50 kb). DNA from glutaraldehyde-treated tissues averaged 20 kb in length, while DNA from all other treatments averaged less than 8 kb in length. Each DNA was subjected to amplification using the polymerase chain reaction, followed by sequencing of 250 bp near the 3′ end of the nuclear rRNA small subunit gene. Glutaraldehyde treatments (at pH 3.0 and 7.0) produced damaged bases at rates of 0.0% to less than 0.1%. Treatments with Lavdowsky's fluid (containing mercuric chloride), FAA at pH 7.0, and SED produced rates of 0.0% to 3.6%. FAA at pH 3.0 produced rates of 7.6% to 15.6%. Nearly 100 attempts to amplify from specimens treated with 3.7% formaldehyde (at pH 3.0 and 7.0) failed, indicating extreme damage to the DNA.