Abstract
Microorganisms are found in almost every conceivable niche of the Earth. They populate every habitable environment, and through their metabolic activity, affect the chemistry and physical properties of their surroundings. They are outstanding chemists and geoengineers, and they did this for billions of years, thus playing an important role in the evolution of the Earth and its atmosphere. Their presence within geologic media has a profound effect on themselves and on the chemical and physical properties of the surrounding environment. Obviously, today spectacular scientific breakthroughs take place between the boundaries of the disciplines of Geology, Paleontology, Chemistry, Physics, and Biology, and new scientific disciplines come up, such as Astrobiology and Geomicrobiology. It is the aim of this chapter to introduce the reader to the fascinating world of microorganisms, and to recognize their important role they have played in the history of the Earth, and still play, in altering our environment. A remarkable number of reactions catalyzed by microbial enzymes have been explored down to the level of protein structure, active site architecture, and specific roles of neighboring amino acid residues. Thus, a lot of once obscure microbiology can be understood nowadays at the atomic level. Notably, numerous geochemical processes observed in the past were discovered through recent years to be catalyzed by microbes, except for those occurring at temperatures beyond 120 °C, the thermal borderline of living organisms. It is the study of microbial interactions with geological media, which advances the exciting field of Geomicrobiology. To speak with microbiologist Bernhard Schink, author of the chapter entitled Microbes: Masters of the Global Element Cycles: “If - after all the great discoveries in chemistry through the last 150 years - chemists may have been tempted to claim “it is all chemistry out there” I tend to oppose: “it is all microbiology - using a highly refined microbial biochemistry”.
