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Thursday, July 28, 2016

Living in a microbial world

Science  29 Jul 2016:
Vol. 353, Issue 6298, pp. 450
DOI: 10.1126/science.aag1515


Microbes have no morals
First we learned to fear germs, then we learned to love our microbiome. But both sides get the biology basically wrong
by Ed Yong

Although they evolved independently, ant-eating mammals—including the pangolin (shown), armadillos, and aardvarks—all possess similar gut microbes.

Once you've experienced “the transformation,” you never look at the world in the same way. For me, it occurred over 3 years of curating a public exhibit on the human microbiome at the American Museum of Natural History. After totally immersing myself in the topic, I viewed every bite of food, every handshake, every scratch of a dog's head through a different lens. How was this action shaping my microbiome—the community of trillions of microorganisms that called my body home? Ed Yong, the author of the new book I Contain Multitudes: The Microbes Within Us and a Grander View of Life, also experienced this transformation, and he's written a delightful, witty book that will surely be a pathway for his readers to do the same.
For most of human history, we were unaware of microbes. Then in the 1670s, the clever Dutch drapemaker Antonie van Leeuwenhoek crafted a handheld contraption that could magnify objects more than 250 times. He used it to explore pond water, insect guts, and samples taken from his own body, observing tiny “animalcules”—the first glimpses of living bacteria and protozoa.
In the ensuing decades, new discoveries linked microbes to human health and showed that certain ones were responsible for specific ailments. This “germ theory” of disease has been the prevailing view in medicine ever since.
With better culturing methods and early DNA sequencing efforts, the census of the microbial menagerie that calls our planet—and our bodies—home began to expand. Next-generation sequencing methods have turbocharged that discovery and revealed a previously unimaginable diversity of novel microbes.
Each one of us has a different pattern of microbial diversity that can correspond to variations in metabolism, disease, and even behavior. This discovery promises to be transformative for medicine and biotechnology. Acknowledging the growing momentum in this field, the White House Office of Science and Technology Policy recently announced the creation of the National Microbiome Initiative, a collaborative effort of federal, public, and private entities to accelerate microbiome science.
In 10 chapters, Yong vividly describes the intricate alliances forged by microbes with every other organism on the planet. He guides us on a historical journey, showing how key discoveries of symbioses, such as early work on the microbes that inhabit termite guts, have been crucial for opening up the “microbiome universe” to scientists. We learn how bacteria allow the Hawaiian bobtail squid to glow, how they permit pea aphids to subsist on nothing but plant sap, and how the wood rat has coopted them so it can digest otherwise toxic creosote. We also learn a lot about parasitic bacteria called Wolbachia that infect insects all over the globe, manipulating their behavior and reproductive fitness. As Yong reveals, these particular bacteria may be useful as a vector control strategy in our fight against disease-bearing hosts like mosquitos.
Any book on microbiomes would be remiss if it did not discuss dysbiosis—a condition in which microbes and host fall out of balance—and Yong does not disappoint, talking about things like emerging Clostridium difficile infections and the collapse of coral reef ecosystems. But he wisely never falls into the trap of labeling any microbes as inherently “good” or “bad” and stops short of predicting how conditions like obesity, infections, and allergies will soon be a thing of the past (as less rigorous journalists have been known to do when writing about this burgeoning field).
The most delightful part of Yong's book is that he does not just tell the stories of microbiomes, he also introduces readers to dozens of the scientists studying them. He visited their labs, met their germ-free mice, and made field trips to the zoo with them. He probed them with questions and captures their motivations and personalities perfectly. Their stories and conversations radiate the excitement of unlocking new secrets, putting a human face on the science.
The title of the book comes from Walt Whitman's classic poem Song of Myself, in which he rejoices in humanity's role in the great ecosystem of Earth. In 1855, Whitman could hardly appreciate the extent of the microbial world, but Yong deftly weaves it into the poet's ode. As Whitman writes: “I am the mate and companion of people, all just as immortal and fathomless as myself.”

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