From staph infections to pneumonia, strep throat to urinary tract infections, we can't help but feel the bacteria around us are alien invaders, designed to hurt, maim or kill us. And if germ warfare has been officially declared, we must do nothing short of destroy our bacterial foils, creating a world of sterile peace through Purell.
Just one problem. We are the microbes that we're fighting.
Our microbiome -- the collection of microbes and their genetic material that live in and on the body -- is packed so full of bacteria, viruses and even fungi that our human cells make up just 10 percent of the cells in our body [source: Yang]. If you gasped to learn that Escherichia coli strains are living on your kitchen counter, you're going to be really upset when you realize they're also happily living in your gut. If you feel squeamish about the live cultures of Lactobacillus in your yogurt, you're probably going to be unhappy to know there's a thriving population colonizing your vagina (or that of someone near and dear to you).
But even with the enormous density and importance of our microbiome, we really know little about it. While we're aware that something like an abundance of the bacteria Clostridium difficile in the gut can cause fatal health issues, we're not sure what a healthy gut looks like. Accordingly, scientists are trying to not just determine how our microbial friends can help or harm us, but also to establish a baseline for a normal microbiome. Much like the Human Genome Project that mapped the entirety of human genes, the Human Microbiome Project is looking to identify the whole of our microbial landscape.
And these microbes aren't just hangers-on. We're hosting more bacteria than our own flesh, blood, muscle -- you name it. Of course, the microbial cells are actually one-tenth to one-hundredth of the size of a human cell, so it's not like we're carrying around a lot of extra weight ... right [source: Kolata]? Nope, we're all schlepping around a substantial 2 to 5 pounds (0.9 to 2.3 kilograms) of bacteria on even the leanest (or cleanest?) bod. (The Hollywood Antibacterial Diet is surely on its way.)
So gather your bacteria, your fungi, your archaea and protozoa by the fire to learn about how the Human Microbiome Project works.