Microbes have an unfairly poor reputation, Ed Yong argues in "I Contain Multitudes," his beautifully written account of the history of microbes and researchers who have explored the vital roles these microscopic creatures play in our bodies and our world. Yong — who like Carl Zimmer belongs to the highest tier of science journalists at work today — weaves revelatory anecdotes and cutting-edge reporting into an elegant, illuminating page-turner that deserves a broad readership.

Yong traces microbes back to their beginnings, when bacteria and archaea (similar in appearance to bacteria but a different domain of microorganism) swam in our planet's early oceans. For more than 2 billion years, these simple creatures were Earth's only inhabitants, until a virtual mathematical impossibility occurred: A bacterium merged with an archaeon, producing a new organism with a nucleus and mitochondria, fuel packs for energy.

From this primal ancestor all multicellular life has descended: funguses and firs, spiders and Sumatran tigers. And, quite recently, Homo sapiens.

"Most microbes are not pathogens. They do not make us sick," Yong asserts, underscoring how microbes nourish our biology, from our gastrointestinal tract to our skin to our sex organs. Microbes outnumber cells in our bodies — we get our first dose from our mothers, as we move down the birth canal; and in mere days they begin to colonize our infant bodies, growing and changing as we grow and change.

Yong takes us on an engaging tour of laboratories where exotic species — flatworms, mosquitoes, Hawaiian bobtail squids — are studied for the microbes they host. The presence of a bacterium called Wolbachia, for example, is closely linked to reproduction in insects. Because of Wolbachia, two nearly identical species of wasps can't successfully mate; their hybrid offspring die shortly after birth. Give the wasps antibiotics that kill Wolbachia, and their offspring thrive. The connections between different microbes shape their destinies, too, as they constantly exchange genes, mutating and adapting to shifts in their environments.

But "I Contain Multitudes" is hardly pure science. Yong paints a lavish mural teeming with vivid characters: talented Antony van Leeuwenhoek, a Dutch lens manufacturer who first observed protozoa in 1675; eccentric Russian Nobel laureate Élie Metchnikoff, who tried to kill himself twice but managed to write an influential book titled "The Prolongation of Life."

Yong asks penetrating philosophical questions, as well: Are we becoming too clean, as the rise of antibiotic-resistant "superbugs" suggests? He notes that populations of affluent, developed countries have less heterogeneous microbiomes than, say, those of indigenous peoples such as the Yanomami in Venezuela, or tribes in Papua New Guinea: "Their multitudes are more multitudinous."

In rich detail, Yong charts the seemingly infinite network of microbial relationships, hub of all life on Earth, concluding that "when we begin to understand our microbiomes, our symbionts, our inner ecosystems, our staggering multitudes, every walk bristles with opportunity for discovery. Every innocuous bush sings with incredible stories."

Hamilton Cain is the author of "This Boy's Faith: Notes From a Southern Baptist Upbringing." He lives in Brooklyn.

I Contain Multitudes
By: Ed Yong.
Publisher: Ecco, 338 pages, $27.99.