ERIC-PCR technique applied to monitoring and quantification of DNA damage during water disinfection process

Abstract

In this work, we propose a novel application of ERIC-PCR technique to study DNA damage after ultraviolet radiation (UV) and peracetic acid (PAA) treatment for water disinfection purpose. The efficacy of both treatments on E. coli suspension was evaluated by two approaches: through monitoring of inactivation by conventional culture technique, and by analyzing DNA damage with ERIC-PCR. All the experiments were carried out in a batch reactor, using three intensities of UV-C radiation (10.5, 4.2 and 2.1 mW/cm2) and different PAA concentrations (4 to 16 ppm). Both treatments produced bacterial inactivation in a dose-response fashion. Based on the results of bacterial count we obtained an index of inactivation (INACI). For each sample, DNA extraction was performed and evaluated by ERIC-PCR. Qualitative modifications were observed in ERIC-PCR band patterns for all the UV-C radiation intensities used, but no changes were detected at any of the PAA concentrations. The banding pattern modifications observed are consequence of the interruption of Taq polymerase enzyme amplification-activity, caused by the presence of alterations on the DNA structure (dimer and hydrates formation). Furthermore, an index was proposed to measure DNA damage (DNADI) regarding the changes in the relative optical density values of the amplification products. A linear correlation was obtained with a high correspondence between the inactivation index (INACI) and the DNA damage index (DNADI), that was expressed as DNADI = 0.05881×INACI. This approach proves that ERIC-PCR is a feasible and valuable tool for detecting and quantifying DNA damage and it may provide a useful strategy for bacterial identification, tracking changes in DNA and providing reliable and reproducible data.