Hrmmm. I’ve already gone and set myself up with an ambitious title. There are so many reasons why we should respect and value microorganisms. Take your own body. Your own “microbiome”- the science word for the community of microorganisms that makes its habitat in and on your body- helps break down your food, absorb nutrients, detoxify harmful chemicals and fight off infections. Our microbiomes contribute to our long-term health in ways we are just beginning to understand.
Or, take the earth. Billions of years ago, microorganisms began respiring oxygen into our atmosphere. Plants and animals would never have evolved had microbes not “primed” our atmosphere, adding greenhouse gases that warmed the surface of the earth and oxygen that provides enough energy to support multicellular life. Today, microbes are intimately involved in the cycling of all the major elements required by life (carbon, nitrogen, phosphorus, oxygen) throughout all parts of the biosphere (air, rock, soil, water).
If nothing else, we are vastly outnumbered by them. There are as many microbes in a spoonful of dirt as there are human beings on the planet. There are more microbes on the entire earth than there are stars in the galaxy. Our own bodies contain ten times more microbial cells than human cells. In a very real sense, each and every one of us is an microbial ecosystem.
In another very real sense, Earth is a microbial planet.
But microbes don’t just outweigh us. The overwhelming majority of our planet’s genetic diversity is found in microorganisms. A rough estimate: there are approximately 150 million different species of prokaryotes (bacteria and archaea) compared with a mere 9 million species of eukaryotes (mushrooms, beetles, us).
Why is this significant? Genes encode proteins that define organisms’ functional capabilities : what they can eat, what sorts of environments they tolerate, how quickly they reproduces. We are a tiny slice of the genetic pie, thus, we are a tiny slice of the functional pie. We eat only organic (carbon-rich) compounds for food – and a limited number of organic compounds, at that. We breathe only oxygen. Microbes eat organic carbon, but also a variety of inorganic compounds including ammonium, sulfur and iron. Microbes respire using oxygen but also nitrogen, iron, sulfur, and methane, to name a few.
In short, by understanding microbes we can begin to get a handle on what is biologically possible within the context of our planet’s unique chemistry and geological history. Microbes define life’s boundaries (and often surprise us by pushing those boundaries further and further away from what we conceive to be “habitable”).
I started this microbe blog to share some of the strange and fascinating ways these tiny organisms make a living.
I’ll kick it off with a link to a BBC report on findings from the Goldschmidt research conference that took place in Florence this past August:
Miles beneath the ocean floor, scientists have discovered some very, very old bacteria. These bacteria are basically metabolically inert, reproducing on average every 10,000 years. With such slow growth rates, can they really be considered alive?