Bacteria

Bacteria. A worldwide war is waged every day based on the simple premise that all bacteria are bad and must be killed. But you should put down that antibacterial wipe and learn to love your bugs. After all, you are hybrid that consists of only about 10 per cent human cells. The collective bacterial genome that lurks within you is so large that it contains between 60 and 100 times as many genes as your human genome. Up to 100 trillion microbes, representing more than 1,000 species, make up a motley 'microbiome' that allows you to digest much of what you eat. Thanks to your single celled passengers, the ecology of your gut is at least as complex as that in soils or seas. It teems with microbial residents that can make vitamins, such as the B vitamins that we cannot synthesize, and can break down plant sugars, such as xylan and cellobiose (similar to cellulose), which humans could not otherwise digest because we lack the necessary enzymes. Our diet would be limited if we could not: cellobiose, for instance, is a key component of plant cell walls that is found in most edible plants, such as apples and carrots. Some bacteria in our guts break down chemicals made by plants that could cause cancer or other illnesses if they were not neutralized. Others can scavenge hydrogen gas - a byproduct of digestion that can kill helpful bacteria - and convert it into methane. In short, these gutsy little helpers keep us alive. And they are designed to be our friends: many of these microbial genes code for enzymes that humans need to digest food, suggesting that bacteria in the colon co-evolved with their human host, to mutual benefit. That is why, the next time you swallow an antibiotic, you should mourn the collateral damage to the diligent little workers in you guts.