Petri Dish: The third branch of life
October 7, 2014
Many years ago as a young biochemistry major at the University of Bath in the UK, I undertook a senior research project with one of the research professors. I remember the project well because of its focus on a very new branch on the tree of life, the archaebacteria. At the time, archaebacteria, a type of bacteria, were thought to live exclusively in extreme environments, such as sites with high temperature or extreme salinity. Since then, it has become clear that they live in many different habitats, including the human gut. But for my research project, I was studying a type of archaebacteria that lives in volcanic vents and is able to flourish in temperatures over 80 degrees Celsius. I remember that growing these critters in the laboratory created quite a few logistical problems given the limited equipment available. The goal of the project at the time was to help isolate enzymes involved in energy metabolism and learn about their structure and function.
The kingdom of life was formerly thought to consist of two main branches — the prokaryotes (bacteria) and the eukaryotes (everything else, the basic distinction between these two groups being that eukaryotic cells have nuclei whereas prokaryotes do not). However, the development of new genetic techniques allowed researchers to study how different life forms are related to one another, an area of science known as phylogenetics. This led to the discovery of a second prokaryotic class which was named archaebacteria by its discoverers, Drs. Carl Woese and George Fox. Archaebacteria disrupted the formerly tidy classification of life and, like all bold ideas, it initially met with considerable resistance from the research community. But further study solidified the archaebacteria's place in the evolution of life, and it is now formally accepted by all scientists. In case you are wondering about the name archaebacteria, it derives from the fact that this new branch of life is considered to be very old, or archaic.
In addition to being an interesting branch on the tree of life, archaebacteria have turned out to be an incredibly valuable source of new products for science and industry. This is because strains of archaebacteria that live in extreme environments have evolved enzymes that are stable at high salinity or at high temperature (unlike proteins from most other organisms that are unstable and inactivated by high salt concentrations and temperature). This has enabled the development of technologies that underpin a variety of industries and also provides many of the tools that drive modern genomics. A good example of this is an archaebacterial species called pyrococcus which thrives in boiling water. Enzymes extracted from this organism are used for both high temperature food processing and amplifying genetic material from tiny samples — a staple of many a "CSI" episode on television. Perhaps even more importantly, these fascinating organisms with their unusual metabolisms may be a source of new antibiotics with novel mechanisms of action. This may be a godsend given the ever-increasing emergence of bacterial resistance to many of our conventional antibiotics.
We now know that archaebacteria are found in habitats all over the planet and are thought to make up almost a fifth of the world's total biomass. Their habitats include our own bodies. In fact, one type of archaebacteria, Methanobrevibacter smithii, makes up almost 10 percent of the microbial flora living in our guts. This particular strain is able to digest methane and also helps remove the end products of bacterial fermentation, thereby aiding digestion. Archaebacteria are also important gut residents in the digestive tracts of animals that have to digest large amounts of cellulose in plants, such as cows and sheep. Thus, archaebacteria are major players in the cycle of life. Yet unlike their bacterial cousins, they have not been associated with disease, making them the ultimate pacifists of the microbial world. And I will be forever grateful for the opportunity to have studied them, even though I did manage to burn out a couple of water baths and start a small fire.
David L. "Woody" Woodland, Ph.D. is the Chief Scientific Officer of Silverthorne-based Keystone Symposia on Molecular and Cellular Biology, a nonprofit dedicated to accelerating life science discovery by convening internationally renowned research conferences in Summit County and worldwide. Woody can be reached at 970-262-1230 ext. 131 or email@example.com.