Fundamentals of Biological Intervention - Environmental Biotechnology: Theory and Application - page 52

number of heat-tolerant extremozymes, for example the major difference appears
to be no more than an increased prevalence of ionic bonds within the molecule.
Though the industrial use of extremophiles in general has been limited to date,
it has notably given rise to PCR, a major technique used in virtually every molecu-
lar biology laboratory worldwide. The application of PCR has, in addition, opened
the flood gates for the application of genetic analyses in many other branches
of life science, including forensics and medical diagnosis. Though this is a tool of
genetic engineering rather than anything which could be argued as an 'environ-
mental' application, it does illustrate the enormous potential of extremozymes.
The process uses a DNA polymerase, called Taq polymerase, derived from
T. aquaticus , as mentioned earlier, and was invented by Kary Mullins in the
mid 1980s. The original approach relied on mesophilic polymerases and since
the reaction mixture is alternately cycled between low and high temperatures,
enzymatic denaturation took place, requiring their replenishment at the end of
each hot phase. Samples of T. aquaticus had been deposited shortly after the
organism's discovery, some 20 years earlier, and the isolation of its highly heat
tolerant polymerase enabled totally automated PCR technology to be developed.
More recently, some PCR users have begun to substitute Pfu polymerase, isolated
from another hyperthermophile, Pyrococcus furiosus , which has an optimum tem-
perature of 100 ◦ C. One area, however, where thermophiles could possibly come
into their own in future is in the production of clean energy, either in terms of
bioethanol production from hemicellulose or in continuous hydrogen production
for conversion in a fuel cell. The former has been investigated using a number
of anaerobic thermophiles, including new isolates of strains growing optimally
at 70 - 80 ◦ C, for their ethanol production from d-xylose (Sommer, Georgieva
and Ahring, 2004) and the latter with several subspecies of Caldanaerobacter
subterraneus (Yokoyama et al ., 2009).
Other extremophiles
As was stated earlier, the thermophiles are amongst the best investigated of the
extremophiles, but there are many other species which survive under equally
challenging environmental conditions and which may also have some potential
as the starting point for future methods of reduced pollution manufacturing. For
example, cold environments are more common on earth than hot ones. The aver-
age oceanic temperature is around 1 - 3 ◦ C and vast areas of the global land mass
are permanently or near-permanently frozen. In these seemingly inhospitable con-
ditions, extremophiles, known as psychrophiles, flourish. A variety of organisms
including a number of bacteria and photosynthetic eukaryotes can tolerate these
circumstances, often with an optimum functional temperature as low as 4 ◦ Cand
stopping reproduction above 12 or 15 ◦ C.
Intensely saline environments, such as exist in natural salt lakes or within the
artificial confines of constructed salt evaporation ponds are home to a group of
extremophiles, termed the halophiles. Under normal circumstances, water flows
from areas of low solute concentration to areas where it is higher. Accordingly,