Microbes from Hell

I recently read about the American microbiologist Carl Woese (1928-2012) and his discovery of a completely new group of single-celled organisms, the Archaea, in Quammen's book The Tangled Tree. These mysterious microbes thrive under extreme environmental conditions, so I was intrigued and keen to find out more. The French microbiologist Patrick Forterre here describes these microbes, the research that led to their discovery, and the questions and answers this has thrown up. Originally published in French in 2008 as Microbes de l'Enfer, The University of Chicago Press has now made this book available in English to a wider audience.

Why the diabolical reference? The answer to that is also the reason that Archaea remained undiscovered for a long time. After the French microbiologist Louise Pasteur in the 1860s showed that you can kill bacteria by heating them (the process of pasteurisation is named after him), it is no real surprise we were predisposed to thinking that life could not possibly exist at very high temperatures. Boil or fry an egg, and the proteins in it will irreversibly change – much the same happens with the proteins of living organisms, rendering them useless. Yet, whether it was happenstance or sheer curiosity, the American microbiologist Thomas Brock discovered microbes in the scaldingly hot pools in Yellowstone National Park in the US in the 1960s. It was Carl Woese who later showed that these heat-loving microbes, or thermophiles, belonged to a completely different group of life forms, the Archaea. Forterre limits this book to heat-loving microbes, though it is worth mentioning that these are a subset of extremophiles which can withstand all sorts of extreme environmental conditions such as high levels of pressure, salt, or radiation.

Next to the history of their discovery, Forterre lets his co-worker and partner tell of the field work involved in sampling such microbes from hydrothermal vents at the bottom of the ocean where they thrive under high pressure, in the dark, and under high temperatures. Probably one of the most interesting chapters talks about the biochemistry and biophysics that allow thermophiles and hyperthermophiles to live at such high temperatures. Why is it that their DNA and proteins do not denature at 85°C, 95°C or even more than 100°C? And is there an upper-temperature limit to life? (Spoiler: yes.) A lot of this has to do with the physics of the atoms that make up biological molecules. You might remember the catchy phrase that "physics is life’s silent commander" from my review of The Equations of Life.

The last two chapters go into the more technical nitty-gritty of where Archaea fit in the tree of life, whether they were the first life forms, and whether they are the progenitors to all eukaryotic life forms (i.e. all organisms that have cells with a separate nucleus such as plants and all vertebrates). The reading here gets fairly technical, looking at ribosomal RNA (though completely not overlapping with Ramakrishnan's story in Gene Machine), viruses and their role in the origin of life, and the various evolutionary scenarios that have been proposed to explain where Archaea fit in the bigger picture, and who is the ancestor of who. Forterre has his own opinions, though it is refreshing to see him explain competing theories, lay out his objections, and indicate where he has changed his mind over time.

Despite the figure of Carl Woese being so important in the history of Archaea, Forterre does not go into much biographical detail in the way Quammen did in The Tangled Tree. The lack of duplication between these two books, then, is fortuitous, and they complement each other nicely. Forterre paces his story well and is brimming with excitement to tell the reader of the history of the science, his own research and that of his colleagues, and the more arcane details of the microbiology and genetics involved. Though the last two chapters will be easier to read if you have a background in biology, this book overall does a great job of making a little-known corner of microbiological research accessible to a wider audience.