The moral of the story is that it is very difficult to tinker with nature and produce an organism that can survive outside the rarefied confines of the laboratory. It takes a certain amount of hubris to believe that we can outdo 4 billion years of natural selection.

Genetic engineering? Nature does it all the time. Scientists call it horizontal gene transfer.

Bacteria can share antibiotic resistance genes. Viruses often encode virulence factors that make bacteria make you sick. Among eukaryotes, examples of horizontal gene transfer are popping up every day among organisms as diverse as plants, nematodes, beetles, and yeast. Even human–gasp–may be riddled with the remnants of horizontal gene transfers: transposons, “jumping genes”, retroviruses, B chromosomes, even our organelles.

Engineering life is as old as life itself. We may be the first to do so in a conscious directed manner, but let’s not kid ourselves into thinking we are the first. There is no doubt there will be mistakes made along the way, but fears of Frankenstein fauna overwhelming nature are vastly overstated. Genetic engineering has already overwhelmingly benefited our lives in ways that most of us are unaware of. Simply put, the benefits have outweighed the costs by several orders of magnitude.

Chakrabarty, A M; Mylroie, J R; Friello, D A & Vacca, J G (1975), “Transformation of Pseudomonas putida and Escherichia coli with plasmid-linked drug-resistance factor DNA.”, Proc. Natl. Acad. Sci. U.S.A. 72 (9): 3647-51, 1975 Sep, PMID:1103151

Jessica asks,

Carl, twice in the book you refer to viruses as “creatures.” Perhaps you used the word metaphorically. In any case I’d love to know whether you think viruses qualify as being alive, and I’d love to hear your reasoning either way.

Historically, viruses have been considered non-living. Some of the first discoverers of viruses, Frederick Twort for example, thought they were enzymes secreted by bacteria. Other biologists, such as Felix d’Herelle, contended that viruses were alive. The distinction lies largely on how “life” is defined.

Viruses certainly do straddle the borderline between the living and the non-living. In some ways, they resemble chemicals. In essence, they are nucleic acids encased in protein. They are inert much of the time, only becoming active on finding and entering a host. They are unable to reproduce on their own. They cannot consume food, breathe, chase prey, respond to the environment in ways typical of the organisms most familiar to us.

But many organisms we classify as living occasionally show the inability to conduct activities we associate with life. For example, is reproducing on its own truly a characteristic of life? Obligate symbioses are common in the biological world. These organisms are unable to survive without the assistance of another organism. For example, some flowers cannot reproduce without assistance from bees. I would argue we are all obligate symbiotes deep down.

The best definition of life I have encountered comes from Salvatore Luria, he of the Slot Machine Experiment ably described by Zimmer in Microcosm.

“An organism is the unit element of a continuous lineage with an individual evolutionary history.”

SE Luria, JE Darnell, D Baltimore and A Campbell (1978). General Virology, 3rd Edn. John Wiley & Sons, New York, p4 of 578.

With this definition, viruses are unequivocally alive. I’ve blogged briefly about this definition previously here.

Photo: A thin section of T4 phages hitting a microcolony of E. coli K-12 by John Wertz.

That is, until now: Microcosm.

And I couldn’t think of a better biographer than science writer Carl Zimmer.

Just this afternoon, I repeated a task I’ve done hundreds, if not thousands, of times: streaked out E. coli onto a plate of agar. As I did, I stopped to think of the opening passages of Microcosm, where Zimmer describes my former lab mate, Nadya Morales, doing exactly the same thing. Formerly this activity seemed so mundane, but now it seemed nothing short of amazing. I was taking some cells from suspended animation at -80C and spreading them on a bit of jelly, and within a day I would see millions upon millions of descendants. Zimmer made it seem positively gripping.

Later Zimmer described how E. coli lives at the brink of exploding, and I thought about how I observed single cells of E. coli being lysed by lambda phage. In less than 1 second after lambda’s proteins made a tiny hole in E. coli’s membrane, E. coli swelled up like a beach ball (well microscopic beach ball) and popped. It’s remarkable to behold, but the drama of what was happening never fully struck me until I read Zimmer’s passages.

E. coli has given us much knowledge of how living things work, but we haven’t retired it to the pasture for old microbes. In laboratories all across the country E. coli continues to reveal life’s innermost secrets. It plays host to my study organisms of choice: bacteriophages, and is used by other scientists to study genetics, evolution, ecology, and microbiology. Thousands of papers are published on E. coli every year. Yet to most people, E. coli is the bug on hamburgers that makes them sick.

Hopefully Zimmer’s book will help rehabilitate the image of this unsung hero of the Molecular Biology Revolution, and let the world know why this humble organism is a favorite of scientists everywhere.

Drawing: E. coli circa 1900 from a color poster used in lectures by Martinus W. Beijerinck, founder of the Delft School of Microbiology, and drawn by his sister Henrietta.