Contrary to popular belief, death is not the end of all systems of cells and organs in the body.
Biologists have revealed that the delicate balance of microbes in a person’s gut remains active years after death.
In fact, the approximately 36 percent of Americans who are buried after death benefits the local environment, serving as a recycling mechanism that creates food for hundreds of species.
The gut microbiome, a complex community of bacteria, viruses, fungi and other microbes that inhabit the body, can remain at work for months or even years after body tissues have broken down.
Scientists at the University of Tennessee simulated the body’s natural decomposition process in a laboratory that combined the type of soil that would fill a grave with the samples of microbes left in the body.
Those microbes lived on even after being deprived of oxygen, feeding on the body’s stores of carbohydrates, proteins and fats.
In addition to being able to survive long after the rest of the body has died, the microbes then mix with the community of microorganisms in the soil to speed up the decomposition process, turning the body into a recycling factory in which new life can flourish.
Americans buried after death contribute to the larger food web and provide fuel for local flora in the form of cyclic nitrogen
According to scientists at the University of Tennessee, microbes remain alive in the dead body for months or even years, feeding on proteins and fats in body tissues
Oxygen-rich blood that has been pumping all your life stops at the moment of death, triggering a complex process in which the body’s cells, deprived of life-sustaining oxygen, begin to digest themselves.
The characteristic odor of rotting bodies is a product of the bacteria feeding on energy-producing processes that do not require oxygen.
Dr. Jennifer M. DeBruyn, an environmental microbiologist at the University of Tennessee, said, “Using your body’s carbon and nutrients, microbes in the body can increase their numbers.
‘A larger population means a greater chance that at least a few will survive in the harsher conditions and successfully find a new body.’
Suddenly and without other biological systems to keep the microbiome population in check, bacteria flourish in the body, metabolizing nutrients from dying tissue to survive.
This process generates fuel as a byproduct for surrounding plants and microorganisms, including ammonia, carbon and nitrogen compounds.
The team of microbiologists from the University of Tennessee and a geologist from the South Dakota School of Mines and Technology wanted to answer two questions: how microorganisms spread through the body to the surrounding soil after death, and also how the mixing of microbes in the soil with those from the body speeds up the decomposition time.
When they mixed microbe-laden body fluids released during decomposition with microbes from the soil, the organic matter from both sources worked together to enhance the release of carbon dioxide and nitrogen, which enrich the soil and local plant life.
Dr. DeBruyn added: ‘One dead animal can support an entire pop-up food web of microbes, soil fauna and arthropods that live on carcasses. Insect and animal scavengers help further redistribute nutrients in the ecosystem.
‘Decomposing microbes convert our bodies’ concentrated pools of nutrient-rich organic molecules into smaller, more bioavailable forms that other organisms can use to support new life.’
In the laboratory, they simulated the natural process of decomposition of a buried body using decomposition fluid from three beavers and soil samples from a plot of land at the University of Tennessee in Knoxville.
In five separate treatments involving 45 different mason jars, scientists placed soil that was either rich in microbes or cleared of all microbes.
The first treatment involved soil that had been cleared of all microorganisms and contained only animal decomposition fluid.
Treatment two allowed all those microorganisms to live in that soil. In the third treatment, scientists mixed the microbe-rich soil with the decomposition fluid.
To simulate nutrient influx, in treatment four they pulsed ammonium to mimic the nutrient release associated with body decay.
In the fifth treatment, only water was added to the soil.
Soil and gas samples taken over the course of six weeks measured the levels of carbon dioxide, nitrous oxide and methane released under three different temperature conditions: 50, 68 and 86 degrees Fahrenheit (10, 20 and 30 degrees Celsius).
Higher temperatures increased CO2 emissions in all scenarios. Treatments two, four and five showed a pattern showing that as the temperature increased from 50 to 68 degrees or from 68 to 86 degrees, the amount of CO2 released in these treatments roughly doubled.
The results of treatment one consisting only of animal microbes were slightly different. CO2 emissions fell between 50 and 68 degrees. But under conditions of 86 degrees, cumulative CO2 emissions doubled compared to the lowest temperature.
The results of treatment three, in which researchers mixed the microbe-rich soil with microbes from beaver carcasses, showed a unique pattern.
The levels of CO2 released at 50 and 68 degrees did not differ much, but increased slightly at 86 degrees.
The fact that CO2 emissions remained high and were even increased at higher temperatures when microbial communities were mixed suggested that together they remain active in the soil for longer and feed the other microorganisms around them.
The microbes derived from the beaver’s decomposition fluid contributed to the production of nitrous oxide and the ability to break down complex nitrogen-containing compounds into simpler forms such as ammonium.
Plants and other organisms then gobble up nitrate and ammonium in the soil generated by the bacteria.
Dr. DeBruyn said: ‘It is not unusual to see plant life flourishing near a decomposing animal, visible evidence that nutrients in bodies are being recycled back into the ecosystem.
‘The fact that our own microbes play an important role in this cycle is a microscopic way in which we live on after death.’
Their findings were published in the journal Ecological Processes.