Each human body contains a complex community of trillions of microorganisms that are important for your health while you’re alive. These microbial symbionts help you digest food, produce essential vitamins, protect you from infection and serve many other critical functions. In turn, the microbes, which are mostly concentrated in your gut, get to live in a relatively stable, warm environment with a steady supply of food.
But what happens to these symbiotic allies after you die?
As an environmental microbiologist who studies the necrobiome – the microbes that live in, on and around a decomposing body – I’ve been curious about our postmortem microbial legacy. You might assume that your microbes die with you – once your body breaks down and your microbes are flushed into the environment, they won’t survive out in the real world.
In our recently published study, my research team and I share evidence that not only do your microbes continue to live on after you die, they actually play an important role in recycling your body so that new life can flourish.
Your microbes accompany you from cradle to grave.
Microbial life after death
When you die, your heart stops circulating the blood that has carried oxygen throughout your body. Cells deprived of oxygen start digesting themselves in a process called autolysis. Enzymes in those cells – which normally digest carbohydrates, proteins and fats for energy or growth in a controlled way – start to work on the membranes, proteins, DNA and other components that make up the cells.
The products of this cellular breakdown make excellent food for your symbiotic bacteria, and without your immune system to keep them in check and a steady supply of food from your digestive system, they turn to this new source of nutrition.
Gut bacteria, especially a class of microbes called Clostridia, spread through your organs and digest you from the inside out in a process called putrefaction. Without oxygen inside the body, your anaerobic bacteria rely on energy-producing processes that don’t require oxygen, such as fermentation. These create the distinctly odorous-gases signature to decomposition.
From an evolutionary standpoint, it makes sense that your microbes would have evolved ways to adapt to a dying body. Like rats on a sinking ship, your bacteria will soon have to abandon their host and survive out in the world long enough to find a new host to colonize. Taking advantage of the carbon and nutrients of your body allows them to increase their numbers. A bigger population means a higher probability that at least a few will survive out in the harsher environment and successfully find a new body.
A microbial invasion
If you’re buried in the ground, your microbes are flushed into the soil along with a soup of decomposition fluids as your body breaks down. They’re entering an entirely new environment and encountering a…
