“About microbes & quoting Whitman, ‘I Contain _______.’” was the $2000 clue in the “Complete the Title” category on the January 2, 2017, episode of television game show Jeopardy. Contestant Katie Carter's correct answer was “Multitudes.” Having just started to review this book, I realized that its reference on the show indicated that it had already become a part of our literary culture.

Throughout most of its history, Earth's only life was microbial. Today we tend to think of nature as a vast and diverse interactive collection of plants and animals all over the planet. Actually, we share Earth with uncounted numbers of microbes, from the deepest ocean trenches to the clouds in the sky. There are more bacteria in a human gut than stars in our galaxy. People often hold the stereotype that all microbes are germs, signs of filth, and sources of dreadful diseases. Most, however, are non-pathogenic, and many are valuable to us. Numerous species exist in symbiotic relationships with the bodies of plants and animals and are the rule rather than the exception. Scientists now realize that, instead of focusing on solitary organisms, microbes must be studied as “communities living in habitats,” specifically host organisms.

This book could change the way we think about microbes by unlocking a wealth of fascinating information on ways they are involved in the lives of animals. A sample of just a few things that most people don't realize about microbes might include the following. Bacteria help maintain the blood-brain barrier by forming cell clusters that block large molecules and living cells from passing into the brain. Microbes convert some insects from one gender to another. In humans, the villain-hero Helicobacter pylori causes ulcers and stomach cancer but protects against esophageal cancer. For a baby to get the most nourishment from breast milk, the bacterium Bifidobacterium infantus must be present. Tropical diseases like elephantiasis and river blindness are caused by nematodes, but it is the symbiotic bacteria released from the nematodes that trigger the immune response in the host, producing the disease symptoms. Many gut microbes involved in digestion contain genes swapped with other species through horizontal gene transfer. Changes in the human microbiome may be involved in obesity, allergies, kwashiorkor, marasmus, and inflammatory bowel disease (IBD). The immune system is not directed by genes alone, but microbes help to shape it and even participate in its operation. Even our homes have distinctive microbiomes, mostly due to the microbiomes of the people living in them.

Beginning with Leeuwenhoek, the first human to see bacteria, Yong's story continues over four centuries to the present with his account of recent successes such as the use of fecal microbiota transplants producing phenomenal results in patients with stubborn digestive problems due to Clostridium difficile. He also comments that, as the book was going to press, clinical trials were beginning for a new multi-microbe treatment for IBD. He notes that microbiologists “find themselves racing to rewrite the relationships between microbes and their animal hosts.” In his final chapter, “Tomorrow the World,” he leaves the door open for the reader to peer into the future and consider what could be coming next. Yong sees great potential for microbiome medicine. He notes that different human microbiomes can actually influence the actions of medications from acetaminophen to digoxin to cancer drugs. He envisions a future where medical treatments might involve custom-made bacteria that will interact with the body's immune system and normal microbiome to tackle many medical issues. The unavoidable conclusion that one might make after reading this book is that “Microbes Rule!”

Yong tightly packs much significant content into the pages of his book. Sometimes, following a particular segment, the reader is almost compelled to pause, reflect, and process what s/he has read and consider whether they might need to reread it. He has researched his subject extensively and communicates his findings in a vivid and richly engaging writing style that, for the reader, is more like reading a well-crafted novel than a brilliant scientific treatise. Complex information is explained in lucid language, often with clever wit and the use of perceptive analogies. He is meticulous in citing his information and explanations in 29 pages of detailed endnotes and a 40-page bibliography. A comprehensive index is also included.

This book would be a valuable asset for the library of any high school or college biology department, where instructors would be well-served to become familiar with the information presented. It could change the way that microbiology, ecology, genetics, evolution, and other areas of biology are taught. Serious biology students would also find the book a valuable resource.