For only a few years, it has been clear that bacteria are completely dominant in a healthy human being: On top of our ten billion body cells, there are one hundred billion microbial cells that play a role in our metabolism. This enormously increases the options for our bodily processes: If we include the microbes’ genes, then we have over 100,000 genes at our disposal, as opposed to just over 20,000.

Researchers...have discovered more than 1,000 new types of bacteria and Archaea over the past 15 years lurking in Earth's nooks and crannies ... Much of this microbial diversity remained hidden until the genome revolution allowed search directly for their genomes in the environment, rather than trying to culture them in a lab dish ... the life we see around us -- plants, animals, humans and other so-called eukaryotes -- represent a tiny percentage of the world's biodiversity.

It’s hard to say which microbes are helping or hurting our health because the science of the “built microbiome” is just beginning. But already, microbiologists know not all microbes are bad. For instance, dog owners’ homes contain dust with a high diversity of bacteria, and studies suggest that exposure to this dust may increase the proportion of bacteria like Lactobacillus johnsonii in dog owners’ guts and help protect them against allergies.

All space missions to an alien world are bound by planetary protection protocols. On Mars, these protocols determine which areas a mission can and cannot land, and how far it can explore after landing ... Areas that are warm or wet enough to support Martian life are out of bounds. Polar ice caps, caves, and regions with volcanic activity are such special regions ... The irony is that all these restrictions mean NASA has to stay away from the very regions where it may find water or Martian life.

Typically, every person is home to about a hundred trillion microbial cells bearing five million different genes, totaling about 5 pounds of micro-organisms per person. Indeed, microbes in and on the body outnumber human cells about 10 to one...The body’s collection of microbes, called the microbiome, influences health in ways that researchers are only beginning to understand...Broadly speaking, city living leaves its mark on people. That includes the sorts of microbes that collect inside them.

many different species were present in the Yanomami's microbiome. The tribe had about 50 percent more ecological diversity than the average American