It's A Small World After All

Journalist Paul DeKruif’s “The Microbe Hunters” became an instant classic upon its publication in 1926. Its tales of scientific adventure, featuring the likes of Louis Pasteur, Robert Koch, and Paul Ehr­lich, inspired an entire generation to pursue careers in medicine, public health, and microbiology. The product of a less jaded time, the book’s heroic scientists offer fearless determination and intelligence to a world overrun with contagion and death.

Three-quarters of a century later, DeKruif’s style can feel nostalgic or even quaint, but his looming shadow does much to explain why it’s such a shock to read a popular book on microbiology in which the microbes are the heroes. Idan Ben-Barak’s “The Invisible Kingdom: From the Tips of Our Fingers to the Tops of Our Trash, Inside the Curious World of Microbes” is a rousting introduction to the amazing ubiquity, utility, and resourcefulness of life too small to see.

It would be impossible to overstate Ben-Barak’s enthusiasm for his topic. His slim volume is full to bursting with excitedly told tales of slime—jet-propelled bacteria, flesh-eating bacteria, hydrazine-producing bacteria, and bacteria that can blink messages in binary code. The average teaspoonful of garden soil contains about 10,000 species of microbes, Ben-Barak informs us, and all of them, he believes, deserve a star turn. If it’s microscopic and is by some stretch of the imagination alive, it’s fair game: paramecia, bacteria, archaea, viruses, and even prions get their due in his book. Unlike most contemporary science writers, who at least pretend to have weighed the scientific importance, investment potential, or social relevancy of their topics, Ben-Barak has decided instead to feature microscopic critters that are either “awesome” or “way cool.”

This straightforward honesty is either refreshing or annoying, depending on your tolerance for jokes about microbial sex, body odor, and the author’s thwarted love affair with toe fungus. Originally published in Australia, “The Invisible Kingdom” is written in a style that might generously be called cheeky but is more likely to strike American readers as puerile. And that’s a shame, because buried underneath all the wisecracks and snarky footnotes are stories that should capture the interest of all citizens of planet Earth.

Microbes truly are everywhere, in great quantity. The ocean-based Pelagibacter ubique, which seems to have no function other than reproduction, has an estimated population of 10²⁸—about 30% of all living things, according to Ben-Barak. Excluding viruses, the average healthy human contains about 2 to 4 lb of microbes; they outnumber human cells by a ratio of 10 to 1. They break down food and waste, make our pickles and beer, transform atmospheric nitrogen into a form we can breathe, and—if you include bacteriophages—kill germs. He recounts how environmental engineers have harnessed their insatiable appetite to clean up oil spills and toxic waste, and how molecular biologists have converted Escherichia coli into gene- and protein-producing factories. The author’s visions for the future include biological information storage and nanowires produced by bacteria.

There’s chemistry, too. Ben-Barak is at his best when describing microbes’ essential role in maintaining the cycle of life, assembling and rearranging seemingly endless combinations of carbon, hydrogen, nitrogen, and oxygen. Many millions of years ago, bacteria had already figured out how to capture energy from the sun and extract nitrogen from the air. When photosynthetic microorganisms first flooded Earth’s atmosphere with oxygen, massive numbers of anaerobic bacteria disappeared. Those that survived developed mechanisms to use oxygen as a source of chemical energy.

Modern plants and animals depend on the energy-transfer mechanisms of bacteria in the form of mitochondria and chloroplasts—organelles that started out as endosymbiotic bacteria before being incorporated into the cell around 2 billion years ago, presumably for the evolutionary advantage they provided their hosts. Yet other bacteria use sulfur instead of oxygen for their oxidation reactions.

Contemporary researchers continue to find new examples of bacteria whose ability to thrive in environments seemingly hostile to life challenges our understanding of the chemical cycle. Hyperthermophiles, or heat-resistant bacteria, can withstand temperatures well above those that destroy the delicate cellular structures of ordinary creatures. Pyrolobus fumarii, for example, thrives at 223 °F in natural chimneys on the ocean floor, far from the sun’s rays. Another, tentatively named Strain 121, survives at up to 266 °F in the Juan de Fuca underwater mountain range about 200 miles offshore from Puget Sound and uses iron rather than oxygen in its metabolic cycle. Hyperthermophiles’ ability to survive extreme conditions has made their enzymes useful laboratory tools in PCR (polymerase chain reaction), a now commonplace technique that allows researchers to amplify tiny samples of DNA into millions of copies through a cycle of heating, cooling, and replication that separates DNA yet leaves the heat-resistant polymerase unaffected.

These moments of lucidity make the author’s insistence on keeping things light all the more frustrating. The book lacks an index and any meaningful list of sources (the “Further Reading” section not so helpfully alerts readers to the existence of Nature and Science), making it difficult to evaluate the accuracy of the author’s claims. Ben-Barak’s insistence on the term “microbe” is particularly troublesome—when you’re not sure whether you’re reading about a bacteria, a protist, a fungi, or a virus, it’s unlikely that you’ll grasp the intricate connections between them.

Given Ben-Barak’s weakness for a racy story, the absence of scientists from the narrative is particularly baffling. Aside from a brief appearance by Barry J. Marshall, the University of Western Australia scientist who drank a sample of Helicobacter pylori to prove that the bacteria causes stomach ulcers, there is little discussion of how the current state of knowledge of the natural world came to be. Instead, he invests the microbes themselves with personality traits usually reserved for characters in a lab drama: We encounter bacteria variously described as clever, friendly, jealous, and, yes, “kinky.” Surely the kind of reader interested enough to pick up a book-length treatment on microbes has the patience for a less gee-whiz treatment of the topic.

With its combination of sincerity and gross-out humor, “The Invisible Kingdom” may be just the thing to turn a teenage boy on to a life in science. While the style may not be to more mature readers’ tastes, the book is nonetheless worth a look for the way that it turns traditional notions of life’s hierarchy upside down. We humans are merely guests on a microbial planet.

Chemical & Engineering News

ISSN 0009-2347

Copyright © 2011 American Chemical Society