Our Life-Long Microbial Companions – Who Are They and What Do They Get Up to While We’re Alive?

Abstract

For the first few hours after death, before any insects arrive, the main drivers of decomposition of the human body are autolysis and the microbes that live on us (known as the “human microbiota” or “human microbiome”). It shouldn’t really come as any surprise to learn that your body is a home to a whole bunch of microbes. After all, we live on a planet that’s densely populated with these creatures – estimates suggest there are approximately 10³¹ of them. That’s an incredible number. To give you an idea of just how big that number is, it’s been estimated that the total number of stars in the universe is 10²⁴ – so there are 10 million times more microbes on our planet than there are stars in the universe. Astonishingly, 18% of the total mass of living creatures (the “biomass”) on our planet consists of microbes whereas animals amount to less than 1%. Not only are there huge numbers of microbes but there’s also an enormous variety – at least 10¹² different species. Microbes are everywhere - in the air we breathe, on the objects we touch and in the food we eat. They’ve colonised virtually all parts of our planet, from the depths of the ocean to the tops of mountains, so it’s no surprise that some of them have made their homes on our bodies.