I’ve always loved the ending of H.G. Wells classic novel, The War of the Worlds. The terrifying aliens who invade the Earth are finally felled–not by guns or nuclear warheads–but instead by the regular old microbes and germs that inhabit the planet.
As Wells’ story illustrates, microbes and humans have been collaborating for thousands of years of co-evolution. What most people don’t realize is that only a few microbes are harmful (i.e., pathogens). The vast majority of microbes carry out essential functions that make air breathable, help digest food, support and protect crops, and clean up chemicals in the environment, among other services. Indeed, life on Earth wouldn’t even be possible without microbes.
Despite their crucial role, microbes are still not well understood. It wasn’t even known that microbes existed until the 17th century when Anton van Leeuwenhoek was first able to see them under a microscope. Until very recently, microbiologists could only study the microbes that could be isolated and cultured in a lab by looking at these one at a time. With the advent of modern genomics (DNA studies), scientists have begun to understand just how diverse and ubiquitous microbes are, accounting for about half the world’s biomass. Today, scientists estimate that there are many millions of microbial species, and of those, less than 1% can be cultured.
Fortunately, there’s a new science that has recently leaped past the need for lab cultures and has put us on a fast track to a better understanding of microbes. The science of “metagenomics,” (sometimes also “environmental genomics” or “community genomics”) turns the power of genomics and bioinformatics on whole communities of microbes where they live. Scientists can take a sample of virtually anything–seawater, soil, or the contents of a stomach–put it into a gene sequencer, and “see” all the things in the sample by analyzing their DNA.
As described in The New Science of Metagonomics (National Research Council, 2006), metagenomics now not only gives scientists access to the many millions of microbes that have not previously been studied, but also begins to provide new information about which microbes are present in a sample and how they work together. It also enables scientists to link other details about the sample–for example, acidity, salinity, and temperature–to the biochemical processes being studied.
Metagenomics can be applied to some of the nation’s toughest challenges. For example, it may lead to the ability to use microbes to break down plant wastes (such as corn stalks) in much the same way as a cow digests hay, providing new sources of renewable energy. Studies have shown a possible link between microbial communities in the stomach lining of mice and whether the mice are fat or thin, a finding which could be of value in understanding obesity. Metagenomics findings are also being applied to cleaning up oil spills, making water drinkable, improving farming, and developing new pharmaceuticals, to name a few examples.
In sum, metagenomics is one of the lesser known, but most important new areas of biology. To learn more, visit a special metagenomics website from the National Research Council. Until next time, don’t forget to be thankful for microbes.
Hi. I’m Barbara Schaal, plant evolutionary biologist, Vice President of the National Academy of Sciences, and Chair of the Division on Earth & Life Studies. In this column, I’ll be writing about topics the division has covered in its expert reports, which are written by committees convened to advise the nation on such topics as climate change, environmental health, agriculture, biosecurity, and many others. My goal is both to share my excitement about many of the topics and, when I can, to offer particular insights that may help people understand the relevance of the scientific findings to their daily lives.