For the brand new study, they discovered that in the soil beneath and near individuals who have been underweight (BMI significantly less than 18.5) and normal weight (a BMI between 18.5 and 26), the diversity decreased in bacterialcommunities. In obese and overweight individuals (with BMIs above 26), the diversity remained mostly constant.
“We consider BMI as a proxy for just how much fat versus just how much muscle we’ve inside our body,” said microbial ecologist Jennifer DeBruyn, Ph.D, at the University of Tennessee’s Anthropology Research Facility, that is also called the “Body Farm.” Those two biological tissues have different chemical compositions that could affect the soil differently.
“We realize from plant litter studies that even slight changes in tissue chemistry can transform the microbial decomposers,” she said. More body fat tissuein a body with higher BMImeans more moisture and an increased ratio of carbon to nitrogen, in accordance with a body with a lesser BMI.
The analysis began, DeBruyn said, with observations by researchers who’d worked for a long time with decomposing bodies at your body Farm. They pointed out that bodies donated and positioned on the soilat once didn’t change just as as time passes. “The bodies experienced identical environmental conditions, but we saw big differences in how quickly they decomposed,” DeBruyn said. That suggested that something in the body, instead of in the surroundings, contributed to the procedure.
For themSpherestudy, the researchers studied 19 bodies that were donated and put into the outdoor facility between February 2019 and March 2020. The ages of the donors ranged from 40 to 91, with a mean of 71, and the BMIs ranged from 14.2 to 55.1. Temperature and humidity data were recorded hourly by remote tags, and the researchers collected soil samples at regular intervals throughout decomposition. In addition they used syringes to get examples of fluids that were released by the bodies and pooled in the soil.
The researchers searched the info for connections. The majority of the bacterial communities in the pooled fluid belonged to theFirmicutesandProteobacteriaphyla, such as dominant species typically within the human gut. A lot of the fungal communities in those fluids were linked to the classSaccharomycetes.But those measurements didn’t explain the variation in decomposition rates.
In the soil round the bodies, they found more diversity in the soil microbe communities than they’d seen in the decomposition fluids.
“My Ph.D. student Allison Mason spent so enough time digging in to the data for just about any explanation of why we saw the differences we did,” DeBruyn said. “And she stumbled on BMI as a predictor.”
Understanding the mechanism behind the observation will demand more work, DeBruyn said. As will other observations made through the study. The soil around people who’d been treated for cancer showed lessmicrobial speciesrichness, for instance, perhaps as the chemotherapeutic agents inhibited the growth of microbes.
However, DeBruyn cautioned that study identified connections between intrinsic factorsand soil microbial populationsbut didn’t show causality. It is a first rung on the ladder toward answering the larger question of howdifferences inhuman bodiesaffects the soil post-mortem, she said.
“The largest problem with one of these humans is that we’re only a big mixed bag of chemicals, so in retrospect this type of study really was not done before,” she said. “Our paperis really among the first touse a big enough sample size of donorsto reveal these patterns.”
More info: Allison R. Mason et al, Body Mass Index (BMI) Impacts Soil Chemical and Microbial Reaction to Human Decomposition, mSphere (2022). DOI: 10.1128/msphere.00325-22
Citation: Study connects decomposing body’s BMI to surrounding soil microbes (2022, September 22) retrieved 22 September 2022 from https://phys.org/news/2022-09-decomposing-body-bmi-soil-microbes.html
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