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25 July 2003

A Valuable Guide to the Bacteria

Betsey Dexter Dyer. A Field Guide to the Bacteria.
Cornell University Press, 2003.
ISBN: 0-8014-8854-0

Reviewed by Jerry W. Kram

Useful biology books for the amateur naturalist can be hard to find, so I was delighted when "A Field Guide to the Bacteria" appeared in an area bookstore. While not without flaws, the book is a wonderful addition to any amateur naturalist's library. It is a witty and comprehensive look at a neglected subject by someone who is very knowledgeable and enthusiastic about the material.

Author and Wheaton College biologist Betsey Dexter Dyer structured the book to be a a true field guide for the amateur naturalist that would also be useful for the professional biologist. Like a birding guide, the book is organized around the different classes of bacteria. Each group is subdivided by habitat, from hot springs to mud flats to deserts to cow pie depending are where they are most likely to be observed.

The book isn't intended to be a comprehensive guide to all bacteria. In particular, disease causing bacteria are treated only briefly for several reasons, mostly because they make up a very small part of the total number of bacterial species and, frankly, they are less interesting than the great diversity of bacteria that aren't pathogenic. Instead, Dyer encourages the reader to look for the visible signs (she calls them "field marks") that indicate bacterial activity in the environment.

Indeed, you and I are field marks for the wild diversity of bacteria that inhabit the human colon and live on our skin, teeth and hair. With a touch of humor, Dyer even lists biologists near hot springs as a field mark for the thermophilic bacteria that are the source of invaluable heat-resistant enzymes for the biotechnology industry.

Dyer leads the reader on an exotic safari from the boiling hot springs of Yellowstone National Park to iron bogs to the backyard garden, from the hindgut of termites to stinky cheese to stinky feet. The scope of the book is hard to capture in a short article. Suffice it to say that almost anywhere you look, you will find bacteria. I was surprised at how many different kinds of bacteria can be identified by the marks they leave on the world.

Dyer encourages her readers to be bacteriocentric and bacteriophilic, at least for a while. She points out several times that there are more bacterial cells than human cells in most people's bodies. She teaches us that we are already familiar with, but usually don't recognize, the ubiquitous signs of bacteria that are all around us. The smell of fresh turned earth (actinomycetes), the taste of yogurt and sauerkraut (lactic acid bacteria) and stained marble and limestone monuments (cyanobacteria) are all indicators of the living bacterial ecosystem around us.

Dyer's approach is a welcome relief from the "Hot Zone" style books that encourage a short-sighted attitude that the only good bacteria is a dead bacteria. She points out that a healthy person is a field mark for a healthy bacterial population.

I think Dyer intends her book to be useful that amateur naturalist will find creative uses for it. I imagined creating a "bacterial banquet" reading Chapter 10, "Gram Positive Bacteria of Food and Beverages." Homebrewers may be intrigued at the intricate microscopic ecosystem that create Belgian-style lambic beers and malolactic wines. Gardeners can learn how much they depend of bacteria to grow healthy and productive crops. She even manages to make a trip to a sewage treatment plant sound interesting and exciting.

The book has the potential to launch a 1,000 science projects. Indeed, one of the reasons Dyer wrote the book was to create a resource for high school teachers. As a judge of many science fairs, she was frustrated that there were hardly any microbiology projects beyond testing household antiseptics.

She describes in detail Winogradsky columns for culturing mixed cultures of bacteria. Indeed, it seems to be difficult to culture many kinds of bacteria without their ecological partners. In particular, Dyer talks about using the columns to create complex sulfereta, ecosystems that depend on the flow of oxidized and reduced sulfur compounds between organisms.

Other sections that seem to lend themselves to experimentation are the sections dealing with microbial mats, photosynthetic bacteria, luminescent bacteria, myxobacteria and magnetotactic bacteria. Just burying glass slides in different environments may yield surprising results as bacteria and other organisms colonize the virgin territory. Enterprising students will no doubt find many ideas in the book that I can't even begin to imagine.

The book isn't without its flaws. I found a number of typos in the book. The most significant was one attributing precambrian stromatolites in Michigan with an age 1.7 million years. Dyer also seems confused at times about her audience's level of sophistication. In discussing using Winogradsky columns for culturing sulfur bacteria, she takes pains to point out that Epsom salt is magnesium sulfate but doesn't let her readers know that calcium sulfate is easily obtained as gypsum.

One oversight in the book struck me as I read her descriptions of fossil traces of bacteria. She spends a number of pages talking about stromatolites and sulfur caves. She has discussion of plant fermenting animals (such as ruminants) and their feces, and twice mentions how the sauropod dinosaurs share many features with those animals. But nowhere does she mention coprolites (fossilized feces). These fossils are fairly common in rock shops and would be likely to interest the young naturalist for the gross out factor if nothing else.

The color plates are a welcome feature of the book, but a few of them are poorly focused. I would have appreciated drawings of the methods she recommends for dissecting the hindgut of termites and crystalline style in molluscs, both interesting sources of spirochete bacteria.

Finally, the discussion of microscopy and culture methods were necessarily limited by Dyer's goals for the book and were mainly limited to the appendices. It would have been helpful if she had included more references on culture methods and basic microscope use.

Overall however, I can recommend this book without hesitation to amateur naturalists, educators and parents as a key to unlocking the door to better understanding the world around them. I hope the book is successful enough to encourage other professional biologists to write similar books on the protozoa, algae and other microscopic wonders.