Extremophiles: Sustainable Resource of Natural Compounds-Extremolytes - Sustainable Biotechnology: Sources of Renewable Energy - page 279

named as such [44]. Radioresistant microorganisms are known to survive in ion-
izing and non ionizing radiation environments, which could otherwise, be lethal
[74]. Certain evidence of past life like microfossils, stromatolites, isotopes of sedi-
mentary carbon and sulphur indicates that microorganisms inhabiting earth during
the Archaean period (the time before 2.5 Ga years) had developed metabolic func-
tions similar to many present day living microbes. The evolutionary relationships of
most of the extremophiles with present day extreme environments indicates novel
genomic pools, biomolecules, and metabolic uniqueness of these microorganisms.
Such extreme environment can be classified as geo-physical extreme (such as tem-
perature, pressure, electromagnetic radiation i.e. ionizing and non ionizing radiation
and cosmic radiation) and geo-chemical extreme including pH, salinity, desiccation,
desert, gaseous toxicants such as reactive species of oxygen and nitrogen, redox
potential, heavy metals etc.
Initially, major applications of extremophiles were identified in the production of
temperature sensitive enzymes of industrial uses [12]. However, other biomolecules
e.g. cryoprotectants, antifreeze proteins, membrane stabilizer lipids, antioxidants,
anti-radiation agents and various other small molecules with therapeutic properties
may be viewed from extremophilic origin. In a revolution of molecular biol-
ogy, Taq DNA polymerase was extracted from a thermophilic bacterium Thermus
aquaticus isolated from a hot spring in Yellowstone National Park USA. Other prod-
ucts of interest are thermostable polymerases and ligases including enzymes like
“Antarctic phosphatase” isolated from psychrophilic (cold-loving) organisms [17].
Genencor TM commercialized one of the first industrial extremozymes for use in
textile detergents [76]. Therefore, in view of the tremendous industrial and therapeu-
tic potential with extreme futuristic applications of the extremophiles, this chapter
aimed to define the sustainable sources of distinguished extreme habitat and their
habitant on the earth. In addition the applications of extremophiles and their prod-
ucts, extremolytes, with their possible implications in the human interest have been
discussed.
2 Extremophilism
Life in any form requires not only an input of the energy but it must be able to control
the flow of the energy. A balance in the redox states of the life chemistry is universal
and need to be maintained unavoidably. An extremophile either lives within natu-
ral organic chemistry parameters, or guard against the outside world in order to
maintain these parameters intracellularly [5]. Organisms that live in more than one
extreme condition are called poly-extremophiles such as Sulfolobus acidocaldarius ,
an Archea that flourishes at pH 3.0 and temperature 80 ◦ C [61].
Other than living in extreme environmental conditions, the extremophiles have
abilities tolerating other adverse environment. Among radioresistant Deinococcus
radiodurans can tolerate 1,000 times more gamma radiation then the other nor-
mal microbial species [62]. Apart from vegetative microorganisms, the spores
(i.e. Bacillus sp.), seeds and egg stages (i.e. shrimp) are more resistant to the
environmental extremes than the vegetative forms. Tardigrades (water bears) in the