Soil Microbial Community Response to Human Decomposition in Michigan's Upper Peninsula

<p>Human decomposition is a complex process influenced by environmental conditions, with predictable patterns in microbial succession offering potential for postmortem interval (PMI) estimation. This study examines the soil microbiome associated with human decomposition at the Forensic Research Outdoor Station (FROST) in Marquette, Michigan – a unique taphonomy research facility characterized by cold temperatures, sandy soil, over 100 inches of snow annually, and close proximity to Lake Superior.</p> <p>Existing soil samples collected from four human donors at three sample sites (Head, Torso, Legs) are the subject of analysis for this project. One donor was placed in summer and three in fall, with sampling spanning from June 11 to November 20, 2021 (up to 106 days post-placement). Following DNA extraction, samples were sequenced using 16S rRNA sequencing, processed with QIIME 2, and microbial community changes analyzed with R using alpha and beta diversity metrics and relative abundance.</p> <p>Results revealed that human decomposition significantly alters the soil microbiome over time. While differences between sampling sites were not statistically significant, emerging trends warrant further investigation. Notably, cold-tolerant bacterial taxa – <em>Paenisporosarcina, Sporosarcina, Marinococcus, Variovorax, </em>and<em> Exiguobacterium</em> – and lakeshore-associated bacteria – <em>Marinococcus </em>and <em>Paraliobacillus</em> – were identified, reflecting the distinct microbial ecology of FROST. A human-associated microbe, <em>Lactobacillus</em>, was detected, while notable insect-associated bacteria and Actinobacteria/Acidobacteria phyla were not.</p> <p>This research highlights the need for climate-specific microbial baselines and increased standardization in forensic soil microbiology. As the field grows, incorporating soil chemistry and long-term studies will be essential for improving understanding of soil microbial community responses to human decomposition.</p>

Name thesis:degree_name

Master of Science

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Biology

Year dc:date.available

2025

Author dc:creator

• Joslyn, Amanda L

Contributors dc:contributor

• Dr. Josh Sharp

• forensic microbiology
• soil microbiome
• human decomposition
• postmortem interval estimation
• taphonomy
• 16S rRNA sequencing
• cold climate decomposition
• microbial ecology
• Upper Peninsula of Michigan
• QIIME 2
• Biology
• Forensic Biology

Repository record dc:identifier

https://commons.nmu.edu/theses/895

OAI identifier oai:identifier

oai:commons.nmu.edu:theses-1959