A novel PCR method for identifying plankton in cases of death by drowning.

We present a new PCR method for identifying plankton in cases of death by drowning. We designed four primer pairs for chlorophyll-related genes of Euglena gracilis (EG) and Skeletonema costatum (SK), which are commonly distributed in water. The primers were selected from sequences coding chloroplast/chlorophyll apoprotein of EG (EG1 and EG2) and fucoxanthin-chlorophyll a/c harvesting protein of SK (SK1 and SK2). With EG1 or EG2, up to 2 fg of EG-DNA was identified, and 0.2 pg of SK-DNA was detectable with SK1 or SK2. No PCR products were amplified from green vegetables (komatsuna, spinach, parsley) or human DNA with the four primer pairs. Regardless of the origin, seawater or fresh water, most diatoms were detectable with primer pairs of EG1 and EG2. With SK1, only Centrales diatoms were identified, and five diatom strains originating from seawater were detectable with SK2. EG1 and EG2 gave rise to PCR products from most water samples. By using Percoll, plankton was easily isolated from human tissue or blood samples and good results of PCR analysis were obtained in cases of death by drowning.