School of Life and Environmental Sciences, Deakin University, Geelong, VIC 3216, Australia.
CSIRO Agriculture and Food, St Lucia, Brisbane, QLD 4067, Australia.
Forensic Sci Int. 2024 Aug;361:112072. doi: 10.1016/j.forsciint.2024.112072. Epub 2024 May 29.
Aquatic decomposition, as a forensic discipline, has been largely under-investigated as a consequence of the highly complex and influential variability of the water environment. The limitation to the adaptability of scenario specific results justifies the necessity for experimental research to increase our understanding of the aquatic environment and the development of post-mortem submersion interval (PMSI) methods of estimation. This preliminary research aims to address this contextual gap by assessing the variation in the bacterial composition of aquatic biofilms as explained by water parameter measurements over time, associated with clothed and bare decomposing remains. As part of three field investigations, a total of 9 still-born piglets (n = 3, per trial) were used as human analogues and were submerged bare or clothed in either natural cotton or synthetic nylon. Changes in the bacterial community composition of the water surrounding the submerged remains were assessed at 4 discrete time points post submersion (7, 14, 21 and 28 days) by 16 S rRNA gene Next Generation Sequencing analysis and compared to coinciding water parameter measurements (i.e. conductivity, total dissolved solids (TDS), salinity, pH, and dissolved oxygen (DO)). Bacterial diversity was found to change over time and relative to clothing type, where significant variation was observed between synthetic nylon samples and bare/cotton samples. Seasonality was a major driver of bacterial diversity, where substantial variation was found between samples collected in early winter to those collected in mid - late winter. Water parameter measures of pH, salinity and DO were identified to best explain the global bacterial community composition and their corresponding dynamic trajectory patterns overtime. Further investigation into bacterial community dynamics in accordance with varying environmental conditions could potentially lead to the determination of influential extrinsic factors that may drive bacterial activity in aquatic decomposition. Together with the identification of potential bacterial markers that complement the different stages of decomposition, this may provide a future approach to PMSI estimations.
水相分解作为一门法医学学科,由于水环境高度复杂且具有影响力的可变性,其研究很大程度上仍未得到充分探索。特定场景结果适应性的局限性证明了需要进行实验研究,以增加我们对水生环境的理解并开发死后入水时间(PMSI)估计方法。这项初步研究旨在通过评估随着时间的推移与穿着和裸体分解遗体相关的水参数测量解释的水生生物膜细菌组成的变化来解决这一背景差距。在三项野外调查中,总共使用了 9 只死胎小猪(n = 3,每批)作为人类模拟物,并将其裸体或穿着天然棉或合成尼龙进行浸入。通过 16S rRNA 基因下一代测序分析,在浸入后 4 个离散时间点(7、14、21 和 28 天)评估了周围水下遗体的水的细菌群落组成的变化,并与同期的水参数测量(即电导率、总溶解固体(TDS)、盐度、pH 值和溶解氧(DO))进行了比较。细菌多样性随着时间的推移而变化,与衣物类型有关,在合成尼龙样本和裸体/棉样本之间观察到显著差异。季节性是细菌多样性的主要驱动因素,在冬季早期和冬季中期后期采集的样本之间发现了大量差异。发现 pH 值、盐度和 DO 等水参数测量值能够最好地解释全局细菌群落组成及其随时间的动态轨迹模式。进一步根据不同的环境条件研究细菌群落动态,可能会确定可能影响水相分解中细菌活性的外源性因素。同时识别出补充分解不同阶段的潜在细菌标记物,这可能为 PMSI 估计提供一种未来的方法。