Every human being has trillions of cells working, dividing, and dying inside their body. Those cells are outnumbered 10 to 1 by bacteria and viruses that take up residence in and around them. We are a walking biome. Every person carries a unique microbe metropolis flourishing inside them. We view bacteria and viruses as dangerous invaders, pathogens, and parasites; yet we can't survive without them.

Bacteria in our guts aid in digestion and oust harmful bacteria (even those that resist antibiotics.) They break down food and heighten our ability to absorb nutrients. This helpful flora is as individual as a fingerprint and may influence our mood. When the bacteria in our gut are in distress, they may alter our brain chemistry and trigger depression, anxiety, and even irritable bowel syndrome.

Viruses, on the other hand, are even more deeply embedded in our bodies. Over millions of years, our ancestors steadily absorbed viral DNA into their own through constant exposure and infection. HERV-K, a retrovirus like HIV, is our most recent attachment. It was still actively replicating when Neanderthals roamed Europe. Such a large influx of foreign DNA can disrupt our genome and increase risk of cancer, but it also can fight off other viruses, may be responsible for the human placenta, and is why humans and dogs share genetic material.

Bacteria is considered life while viruses are non-life. Both are busy tenants making a life for themselves in a cradle of cells that only you can provide.

(Image credit: Brian0918, Wikipedia)