We think humans rule the world, but the reality is that Earth is dominated by microbes. Microbes are mostly single-celled creatures, and they have existed on Earth for more than 3.5 billion years. They occupy almost every ecological niche — from hot springs in Yellowstone, to acidic mine waste, even on and in our bodies, where they outnumber our cells by more than 100 times. Humans have used these diverse creatures for millennia. Bread, cheese, yogurt, beer and wine are among the vast array of food products that utilize microbial action. In industry, microbes are used to produce chemicals, make our favorite foods and even to clean up oil spills.
Some microbes called pathogens can cause disease in humans, including dental decay, skin infections, and intestinal disease. It is thought that up to 60 percent of all cancers have a microbial origin. Microbes are truly a Jekyll and Hyde dilemma for humans.