After Death, the Necrobiome Helps Drive the Circle of Life

Eric Benbow and some colleagues had some beers when Benbow found a new term for what they studied: the necrobiome. Although it seems rather Lovewftian, the necrobiome simply refers to all the organizations associated with a decomposition organization.

This includes everything, from microbes to insects, nematodes and vertebrate, avian and terrestrial scavengers, explains Benbow, an environmentalist at Michigan State University who studies necrobiome.

What is the necrobiome

When an animal dies – and that includes you, dear reader – the members of the necrobiome, inside and outside, begin to break down the body. The first to start snacking are the microbes that live in you, especially in your intestine. While you are alive, these microbes are controlled by your immune system. But once you are dead, the immune system no longer works.

It is at this point that “they turn against us and begin to digest us from the inside,” explains Jennifer Debruyn, environmental microbiologist at the University of Tennessee who studies decomposition and biodegradation.

Our cells no longer receive oxygen (because we no longer breathe), so they die and release macromolecules such as carbohydrates, proteins and lipids. Microbes use these macromolecules as food and energy sources, she explains.

Because there is no oxygen in the internal cavity of the body, this process is a type of anaerobic fermentation. And this produces a lot of gas, often causing swelling of corpses. This is why they have this unique smell. When you hike in the woods and you feel a dead animal, you mainly feel microbed pets.

Soon, however, internal microbes are joined by decomposers from the outside. They are mainly bacteria and fungi.

“A corpse is a fantastic resource for them because it is full of nutrients and humidity,” explains Debruyn. Finally, insects and vertebrate scavengers, such as vultures, foxes and raccoons, join the party.

The necrobiome also breaks down plants. This is what is happening in your compost pile or in the litter of leaves in the woods.

Learn more: Worms can feel death, and it strangely changes their fertility and physical shape

Draft

One of the interesting research questions for Debruyn is what happens to these internal microbes after finishing digesting what was once their house. His initial hypothesis was that intestinal microbes do not last very long in the outside world. Inside, they had very favorable conditions. The temperature was always 37 degrees Celsius (98.6 degrees), there was a regular supply of nutrients and no oxygen.

“So they had this fairly comfortable life,” she said. “My hypothesis was that once they came out in the ground environment, it’s like the West West. There are huge fluctuations in temperature, humidity, pH that they do not see normally.”

But when she started investigating, she was surprised. In a study, she and her team followed the DNA of a human intestinal microbe in the soil while a body was decomposed. This particular bacteria needed an oxygen -free environment to live. However, they found that it lasted several months in the ground. She suspects that the microbe has survived by remaining inside the fat and fat pools made by the body while it breaks down.

This “sticky disorder”, as Debruyn says, would lead to anoxic the soil in this area. In a later experience, she has shown that intestinal microbes are not dormant in this sticky disorder; They are always active and involved in decomposition.

Microbes can help detectives

Not only recycling necrobiome, but it also provides a lot of information. Experts can have a good idea of ​​the duration of a dead body by examining the insects that colonize it, in particular their number, their type and the stage of their life cycle. This information was used in courts around the world, says Benbow.

The succession of bacteria and fungi on a corpse is also informative. Benbow and his colleagues have shown that the analysis of a swallowing of a dead organization can show how long the organization is dead. However, this method has not yet been used in court. Arriving at this point would require more studies, including studies on humans, to develop robust models for the method. It can take time, because there are not many people who do this kind of research, explains Benbow.

The necrobiome can also tell you if a body was moved after death. Bacteria could be useful in this regard. The soil on the site of a murder could reflect the microbial activity associated with human decomposition, even if the body has been moved to another place, explains Benbow.

Circle of life

Whether it is an animal that dies of natural causes or an unfortunate victim of murder, the necrobiome modifies the local environment. The composition of the soil changes, as is when the dead plant material turns into humus.

The vertebrate scavengers also play a role here. Birds, for example, will often challenge and around a corpse. If they have recently ate seeds from another area, they mainly plant these seeds. If the acidity of the soil and the nutrients are correct, the plants could be established. Whole plant communities can change because the carcass has attracted a trapping that brings these seeds, explains Benbow.

Although we tend to see death as a tragic event, for nature, it is part of the cycle of life and death. And without the necrobiome to maintain the cycle, we would be “covered with dead stuff”, explains Debruyn. “The decomposers are so essential and so underestimated.”

Learn more: Why don’t we see more remains of dead animals while walking in the woods?

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