Each person’s body contains a complex community of trillions of microorganisms that are important to health for as long as the person lives. These microbial symbionts help digest food, produce essential vitamins, protect the body from infection, and perform many other important functions.

In contrast, microbes, mostly concentrated in the human gut, live in a relatively stable, warm environment with a constant food supply. So what happens to these symbiotic allies after the biological death of the body? Jennifer De Bruyne, professor of environmental microbiology at the University of Tennessee, says the following about this:

“As an environmental microbiologist who studies the necrobiome (the microbes that live in, on, and around decomposing bodies), I was curious about our postmortem microbial legacy.

You may assume that your microbes die with you; When your body breaks down and your microbes are released into the environment, they cannot survive in the real world. In our recently published study, my research team and I share evidence that your microbes not only survive after you die, but also play an important role in rebuilding your body so that new life can thrive.

When you die, your heart stops pumping blood that carries oxygen to your body. Cells deprived of oxygen begin to digest themselves in a process called autolysis.

Enzymes in these cells, which normally digest carbohydrates, proteins and fats in a controlled manner for energy or growth, begin to affect the membranes, proteins, DNA and other components that make up the cells.

The products of this cellular breakdown are excellent food for your symbiotic bacteria, and without a constant source of nutrients from your immune system and digestive system to keep them in check, the bacteria will turn to this new food source. Gut bacteria, specifically a class of microbes called Clostridia, spread into your organs and digest you from the inside in a process called putrefaction.

When there is no oxygen in your body, your anaerobic bacteria rely on energy-producing processes that do not require oxygen, such as fermentation. They create signs of decomposition of distinctly odorous gases.

From an evolutionary perspective, it makes sense that your microbes would have evolved to adapt to a dying body. Like rats on a sinking ship, your bacteria will soon be forced to abandon their host and survive on earth long enough to find a new host to colonize.

Using your body’s carbon and nutrients allows you to increase their amount. “A larger population means that at least a few individuals are more likely to survive the harsh environment and successfully find a new body.”

microbial invasion

“If you are buried in the ground, as your body decomposes, your microbes mix with the decomposition fluids. They enter a completely new environment and encounter a whole new community of microbes in the soil. In nature, mixing or merging of two different microbial communities often occurs. Fusion occurs when the roots of two plants grow together, when sewage flows into a river, or when two people kiss.

The outcome of mixing (which community is dominant and which microbes are active) depends on several factors, including how much environmental change the microbes have undergone and who got there first.

Your microbes adapt to the stable, warm environment inside your body and are constantly nourished there. In contrast, soil is a particularly challenging place to live; It is a highly variable environment with sharp chemical and physical changes and large fluctuations in temperature, humidity and nutrients.

In addition, soil already hosts an extremely diverse microbial community; It is full of decomposers that are well adapted to this environment and will likely outcompete the newcomers. It’s easy to assume that your microbes will die when they leave your body. However, my research group’s previous work has shown that DNA signatures of host-associated microbes can be detected in the soil beneath a decomposing body, on the soil surface, and in graves for months or even years after the body’s soft tissues have decomposed.

This raised the question of whether these microbes were still alive and active, or were they dormant, waiting for the next host. Our latest research shows that these microbes not only live in the soil, but also work with natural soil microbes to help your body break it down.

In the laboratory, we have shown that mixing soil and decomposition fluids loaded with host-associated microbes increases the rate of decomposition.

We also found that host-associated microbes increase nitrogen cycling. Nitrogen is an essential nutrient for life, but most of Earth’s nitrogen is in atmospheric gas that organisms cannot use.

Decomposers play an important role in converting organic forms of nitrogen, such as proteins, into inorganic forms, such as ammonium and nitrate, that can be used by microbes and plants.

Our new findings suggest that our microbes likely play a role in this recycling process by converting large nitrogen-containing molecules, such as proteins and nucleic acids, into ammonium. Nitrifying microbes in the soil can then convert the ammonium into nitrate.”

Next generation life

“The recycling of nutrients from detritus or non-living organic matter is a fundamental process in all ecosystems. In terrestrial ecosystems, the decomposition of dead animals or carcasses nourishes biodiversity and is an important link in food webs.

Living animals are a bottleneck for carbon and nutrient cycles in an ecosystem. During their lives they slowly accumulate nutrients and carbon from large areas of the landscape, then when they die they deposit it all at once into a small, localized spot.

A single dead animal can feed a food web of microbes, soil fauna, and arthropods that subsist on the corpses. Insects and scavengers help further redistribute nutrients in the ecosystem. Degradative microbes convert nutrient-rich organic molecules in our bodies into smaller, more bioavailable forms that other organisms can use to support new life.

It is not uncommon to see plant life thriving near a decaying animal; This is clear evidence that nutrients in the body are recycled into the ecosystem. “Our own microbes play an important role in this cycle, which is one of the microscopic ways we live after death.” Source