Plankton DNA Detection in Organ Tissues of Drowned Bodies According to Different Aquatic Environments in the Lower Reaches of the Nakdong river

다국어 초록 (Multilingual Abstract)

This study aimed to help distinguish antemortem drowning from postmortem immersion across freshwater (FW), brackish water (BW), and seawater (SW) using controlled rat submersion models and plankton-derived DNA analysis in internal organs. Environmental water was examined microscopically, and major organs from drowning, postmortem immersion, and control rats were evaluated by H&E staining. Lung DNA was tested using published universal primers targeting cyanobacterial 16S rRNA (FW) and diatom rbcL (SW); Sanger sequencing was performed when amplification was obtained, and interpretable regions were analyzed by BLAST. Microscopy suggested water-type differences, with cyanobacteria more frequent in freshwater, diatoms more prominent in seawater, and brackish water showing a mixed community. Histology showed plankton-like particles mainly in lung sections, while other organs lacked morphologically clear structures, underscoring the limits of morphology alone. Freshwater lung DNA was amplified with the cyanobacterial 16S primer set and sequenced; despite mixed/noisy chromatograms, BLAST of readable segments suggested lineages related to Microcystis and Oscillatoria. In contrast, although the rbcL primer set amplified a diatom reference material, no rbcL amplicons were obtained from seawater lung extracts under the tested conditions, preventing sequence-based diatom identification. Overall, integrating environmental microscopy, lung histology, and exploratory PCR with Sanger sequencing enabled recovery of plankton-derived signals from freshwater lung tissue and provides preliminary information to guide optimization and development of more specific, environment-targeted primers for forensic drowning assessment.

목차 (Table of Contents)

• Abstract i
• List of Tables v
• List of Figures vi
• Ⅰ. Introduction 1
• Ⅱ. Materials and Methods 7
• 1. Study design 7
• 2. Experimental animals and ethical approval 9
• 3. Environmental water sampling and microscopic examination 10
• 4. Establishment of drowning and postmortem submersion models 12
• 5. Organ dissection and sample storage 14
• 6. DNA extraction and quantification 15
• 7. Conventional PCR and qPCR 16
• 8. Sanger sequencing for target identification 21
• Ⅲ. Results 22
• 1. Environmental characteristics and plankton composition 22
• 2. Histological findings in organ tissues 27
• 3. Conventional PCR and qPCR results using universal primers 33
• 4. Sequencing results of PCR-Amplified products 40
• Ⅳ. Discussion 43
• References 47
• Abstract in Korean 53