Life extreme habitats

Astrobiological research is, however, not only concerned with the search for life on other heavenly bodies it also includes work on life forms in extreme habitats, in hydrothermal systems and, for example, in deep rock formations (Pedersen, 1997) (see Sect. 7.2.1). 

A very interesting research area in biology and biotechnology is the topic of extremophiles. Life on Earth has adapted over the course of evolution, even to extreme habitats (although there is evidence that organisms had to adapt to ever cooler conditions on Earth over the course of early evolution). Extreme habitats encompass the range of conditions as described ... 

The Archaea are similar to bacteria and until 1977 most known species were classified as bacteria (see review by Makarova and Koonin, 2003). It was the work of Carl Woese (see Woese and Fox, 1977) who discovered that some so-called bacteria were different genetically and separated the Archaea from the bacteria on the basis of particular rRNA sequences present in the cells of the organisms. The Archaea in existence today are thought to have descended from the first forms of life to have evolved on Eardi some 3.5 to 4.0 x 10 years ago. This relates to the fact that many (but not all) members of the existing Archaea are anaerobic, i.e. they do not require oxygen for survival, and thus could inhabit a world with an oxygen-poor atmosphere as was the case during the early history of the Earth. They also survive under extreme habitats today (see Table 3.2) and so could have tolerated the harsh conditions of the newly-formed planet. 

In other words, most organisms will have evolved to survive with chemical diversity in their environment. An organism exposed to a new natural or synthetic chemical will simply have one extra chemical in its environment. For reasons discussed in Chapter 5, the chances are extremely small that the new chemical will possess the particular properties that endow it with the potential to reduce the fitness of the organism. For billions of years, individuals of all species will, at intervals, have been exposed to a chemical that they have not encoimtered before. This will be a situation that might have happened many times in the lifetime of some individuals. It is certainly a circumstance that will have arisen many times in the recent evolutionary history of many species when species have increased their habitat range with the result that they inevitably encounter NPs that are novel to them. In other words, being exposed to new chemicals is a normal part of life. A good example of this fact comes from humans. Humans have been very... 

By generally clement Earth standards, the habitats for life on Mars and Europa are likely to be extreme environments. On the other hand, extrater-... 

The diversity of microbial life is, in part, a result of the interactions between an extremely heterogeneous and complex habitat (the soil), variable nutrition sources (both in structure and availability), numerous trophic interactions (including competition and predation), and multiple methods of gene flow. For additional information on soil microorganisms the reader is referred to the texts of Paul and Clark (1996) and Sylvia et al. (1999). 

Life on earth has radiated to exploit virtually every conceivable habitat and lifestyle. Life persists at the extremes of environmental temperature (from -50°C to > 90°C) and in the depths of the ocean (at hydrostatic pressures of up to 500 atm). Desert... 

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