Soil microbial gene expression over one year of human decomposition

Area of Science:

• Microbial ecology
• Biogeochemistry
• Decomposition science

Background:

• Terrestrial vertebrate decomposition involves complex interactions between host and environmental microbes.
• Decomposition hotspots experience significant microbial community restructuring and altered biogeochemical cycling.
• Understanding the succession of active microbes and their metabolic pathways during decomposition is crucial.

Purpose of the Study:

• To investigate the succession of active microbial communities (bacteria, archaea, fungi) during human decomposition.
• To identify the metabolic pathways utilized by these microbes throughout the decomposition process.
• To assess the temporal effects of human decomposition on soil microbial gene expression.

Main Methods:

• Collection of soil samples from beneath decomposing human bodies over a one-year period.
• Generation of metatranscriptomes to analyze active microbial communities and their gene expression.
• Analysis of microbial gene expression related to stress response, nutrient cycling, and specific metabolic functions.

Main Results:

• Soil microbes exhibited increased expression of heat shock proteins due to altered physiochemical conditions (hypoxia, high salinity).
• Fungal lipase gene expression indicated fungi's role in fat decomposition, while nitrogen cycling genes showed phased expression correlating with oxygen availability.
• Increased bile salt hydrolase expression suggested a microbial origin for high taurine concentrations observed in decomposition environments.
• Microbial gene expression profiles remained significantly altered even after one year post-decomposition.

Conclusions:

• Human decomposition profoundly impacts soil microbial gene expression, altering community structure and function.
• Microbial responses include adaptation to environmental changes and specialized roles in nutrient cycling.
• The effects of decomposition on soil microbial communities are both transient and persistent, lasting up to one year.