2023-10-04 18:17:00
What if this was “life following death”? Jennifer DeBruyn, Professor of Environmental Microbiology, University of Tennessee, has a specialty all her own: she studies the necrobiome, that is to say the microbes that live inside, on the surface and around a decomposing body.
“Each human body contains a complex community of trillions of microorganisms [bactéries et champignons microscopiques] which are important for your health while you are alive”recalls the researcher in The Conversation (September 28, 2023).
“These microbial symbionts help you digest food, produce essential vitamins, protect you once morest infections and perform many other vital functions. In return, the microbes, which are primarily concentrated in your gut, can live in a relatively stable environment and warm, with a regular supply of food.”
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Recycling of the body
It is therefore a win-win relationship, as we will have understood. But what happens when you die? This is what Jennifer DeBruyn and her colleagues, authors of an article in the journal, wanted to determine Ecological Processes (September 11, 2023).
“You might think that our microbes die with us: once our bodies break down and our microbes are released into the environment, they do not survive in the real world”she notes. “In our recently published study, my research team and I share evidence that not only do your microbes continue to live following you die, but they actually play an important role in recycling your body so that a new life can flourish.”
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The researcher specifies that when you die, the heart stops circulating blood carrying oxygen throughout the body. Cells deprived of oxygen begin to digest themselves in a process called “autolysis”, the action of their enzymes redirecting to membranes, proteins, DNA and other components of the cell .
Or, “the products of this cellular breakdown provide excellent food for symbiotic bacteria and, in the absence of an immune system to control them and a regular supply of food through the digestive system, they turn to this new source of food “she summarizes.
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Putrefaction
In the next step, sensitive souls refrain! Gut bacteria, particularly a class of microbes called Clostridia, spread through your organs and digest you from the inside through a process called “putrefaction”. In the absence of oxygen inside the body, “anaerobic” bacteria rely on energy-producing processes that do not require oxygen, such as fermentation – which emits odorous gases characteristic of the decomposition.
“If you’re buried, your microbes are released into the soil with a soup of decomposition fluids as your body decomposes. They enter an entirely new environment and encounter an entirely new microbial community in the soil”pour suit Jennifer DeBruyn.
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I was there before…
When two distinct microbial communities meet, it’s called “coalescence” – a process that occurs, for example, when the roots of two plants grow together, when sewage is dumped into a river, or, more romantically, when two people kiss.
“The outcome of mixing – which community dominates and which microbes are active – depends on several factors, such as the extent of environmental changes experienced by the microbes, and who was there first”underlines the researcher.
“Microbes are adapted to the stable, warm environment inside the body (…). On the other hand, the ground is a particularly difficult place to live: it is a very variable environment. in terms “temperature, humidity and nutrients.”
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Furthermore, the soil already hosts an exceptionally diverse microbial community, full of “decomposers” well adapted to this environment and which would likely outcompete any new arrivals. It is therefore easy to assume that microbes die once they are outside the body.
However, previous studies by the microbiologist and her team have shown that “signatures ADN” Microbes associated with the host (human or other animal) might be detected in the soil beneath a decomposing body, on the soil surface, and in graves for months or years following the soft tissues of the body had decomposed .
Nitrogen cycle
It remained to be seen whether these microbes were still alive and active, or whether they were simply in a dormant state waiting for the next host. “Our latest study suggests that your microbes not only live in the soil, but also cooperate with native soil microbes to help break down your body”assure Jennifer DeBruyn.
“In the laboratory, we showed that mixing soil and decomposition fluids filled with host-associated microbes increased decomposition rates beyond those of soil-only communities”she explains.
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In addition, the researchers also found that our microbes contribute to the nitrogen cycle, an essential nutrient for life and most of which on Earth is blocked in the form of atmospheric gas, unusable by living beings. Soil decomposers play an essential role in recycling organic forms of nitrogen (proteins) into inorganic forms (ammonium and nitrate), which microbes and plants can use.
“Our new findings suggest that our microbes likely play a role in this recycling process, converting large nitrogen-containing molecules, like proteins and nucleic acids, into ammonium. Nitrifying microbes in the soil can then convert the ‘ammonium to nitrate’she adds.
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A new generation of life
The recycling of nutrients contained in detritus, or non-living organic matter, is an essential process in all ecosystems, including within terrestrial ecosystems where the decomposition of dead animals, or carrion, fuels biodiversity and constitutes an important link in food networks.
“It is not uncommon to see plants thriving near a decomposing animal, visible evidence that nutrients in the bodies are being recycled back into the ecosystem”, concludes the researcher. And to add:
The fact that our own microbes play an important role in this cycle is one of the microscopic ways we continue to live following death.
On the same topic :
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