Warning: If you have a squeamish stomach, you may want to skip over some of the details here.
I'm back again with more microbe news, this time from the New York Times. From the moment we're born, we're constantly being colonized by different types of bacteria. In fact, the microbes in our bodies outnumber the human cells by a factor of 10 to 1. Each part of the body is home to different types of bacteria; the mouth alone can have up to a thousand different species. But before you run for the nearest bottle of Scope, don't panic; not all of these bacteria are going to make you sick. In fact, some of them are necessary to produce enzymes to help you digest certain types of food or prevent more harmful bacteria from settling in. Without exposure to microbes early in life, the immune system doesn't develop normally, which can possibly lead to asthma and autoimmune disorders. (It's nice to know the six-month stretch of musical colds/ear infections our family endured when our son first entered daycare may actually be good in the long run.) Scientists are now starting to study the populations of microbes in our bodies; this collection is called the microbiomes. Each person has a unique microbiome, and the microbiome can change in response to illness. For example, when our son was on antibiotics for ear infections, we needed to give him yogurt to replenish the good bacteria in his digestive tract. One doctor has even performed what could be called a microbial transplant, giving a woman who had a severe bacterial infection some of her husband's bacteria. The woman had lost 60 pounds due to diarrhea that had lasted for months, but the diarrhea disappeared a day after the transplant.
So, what can a science fiction writer do with a microbiome? For starters, you can explain why some people are resistant to some diseases while others aren't. You can even use the microbiome as a way to create differences in identical twins; they may have the same human DNA, but not the same microbes. I'm personally intrigued by what would happen when humans go into space or visit other planets. If you're stuck in a spaceship for a long time, without exposure to other new microbes, will that have an effect on your own microbiome? What happens when you go to another planet? Is it possible to find extraterrestrial microbes compatible with the human body? While it seems unlikely the biochemistries would be similar, microbes have short generation times and perhaps could evolve to work with us. Perhaps we might even develop a symbiotic relationship with them. Like all tools, bacteria can be used for good or bad purposes; it all depends on what you want to do with them.