Microbes 101: An Introduction
You probably don’t care much for microbes. They cause disease. They smack of being unclean. They are a reason we wash our hands. They cause the plague, influenza, Giardia, Ebola, and the common cold. We stockpile antibiotics and build hospitals to fight infectious diseases, and fund scientific research focused on how to prevent epidemics. Dealing with the negative effects of microbes requires a large effort on our part, and you might feel we’d be better off without them. But let’s put things in perspective. Our planet formed roughly 4.6 billion years ago. The oldest lifeforms we have found evidence of are microbes, fossils of tiny single-celled creatures in ancient hydrothermal vent rocks, dating to 3.8 billion years ago, hundreds of millions of years before evidence of large, multicellular organisms appears: the first land plants (600 million years ago), dinosaurs (250 million years ago), flowering plants (100 million years ago), and modern humans (at least 200,000 years ago). Billions of years before humans were even a possibility, and for the vast majority of Earth’s history, microbes were here. Not only did all other life evolve from microbes (yes, microbes are your extremely distant ancestors), but all of life has evolved in an environment filled with and shaped by microbes. As a result, humans and every other organism on Earth have intimate, often life-sustaining relationships with microbes.
So, despite their bad reputation, microbes turn out to be crucial for life on Earth. But because they are so small, their benefits have long gone under the radar. More recently, thanks to research ranging from geology, to oceanography, to medicine, we’ve begun to better appreciate what these teeny creatures are up to. There are 7 billion humans on Earth, and each harbors billions of microbes. Without us ever noticing, they’re in our bodies helping us digest food, protecting us from disease, even shaping our anatomy. And more than just in us and on us, they are also all around us: on our clothes, our pets, in our yards, in our houses. They are at the bottom of the ocean, in the hottest deserts, and in the glaciers of Antarctica. In every habitat you can imagine, microbes are living, thriving, and playing crucial roles such as decomposing and recycling dead matter, and producing oxygen for our atmosphere.
From our guts to hydrothermal geysers, how do microbes manage to take on such varied lifestyles? In the first place, lumping all microbes together is a bit like mixing together all the animals in the zoo. In addition to taking up the entirety of two of the three major sections of the Tree of Life with bacteria and archaea, there are also fungi, protists, and viruses. (More on all this later.) But even if we just look at the most stereotypical of microbes, bacteria, we find incredibly diverse biochemistry in terms of the enzymes they produce, the materials they can break down and process (metabolize), and the molecules they can synthesize. In other words, the big organisms have bodies or structures that are diverse, while bacteria chemistry that’s diverse. This diversity in biochemistry leads to immense variation in the places microbes can live and environments in which they thrive, conditions we humans would consider inhospitable. Some microbes thrive in extremely hot temperatures that would kill any known multicellular life. Other microbes are adapted to live in stomach acid, hydrothermal vents at the bottom of the ocean, or pools filled with lead or mercury.
We depend on the amazing biochemical diversity of microbes for our own survival. Microbes are the fundamental underpinning of the way our planet works. We are still learning a lot about the diversity of microbial life; identifying new microbes and sequencing their genetic toolboxes has given us a wealth of information to decode and tap into.
Since humans first discovered microbes a few hundred years ago, we have portrayed them in a negative light much more often than a positive one. Take a step back onto neutral ground for a moment: breathe the air, take in the scenery, enjoy a meal. Appreciate and explore the crucial roles of microbes within you and across the planet. We are not alone. We — and our entire world — contain multitudes.
*Image credits: Google Creative Commons.
Contain Multitudes is a multi-part video series dedicated to exploring the wonderful, hidden world of the microbiome. The series is hosted by science writer Ed Yong and produced by HHMI Tangled Bank Studios in association with Room 608.
