Fundamentals of Biological Intervention - Environmental Biotechnology: Theory and Application - page 54

A number of species, for example, accumulate potassium chloride (KCl) in their
cytoplasm, with the concomitant result that extremozymes isolated from these
organisms will only function properly in the presence of high KCl levels. By
the same token, many surface structural proteins in halophiles require severely
elevated concentrations of sodium salts.
Acidophiles thrive in the conditions of low pH, typically below 5, which occur
naturally as a result of sulphurous gas production in hydrothermal vents and
may also exist in residual spoils from coal-mining activity. Though they can
tolerate an externally low pH, an acidic intra-cellular environment is intolerable
to acidophilic organisms, which rely on protective molecules in, or on, their
cell walls, membranes or outer cell coatings to exclude acids. Extremozymes
capable of functioning below pH1 have been isolated from these structures in
some acidophile species.
At the other end of the spectrum, alkaliphiles are naturally occurring species
which flourish in soda lakes and heavily alkaline soils, typically enduring pH9 or
more. Like the previous acidophiles, alkaliphiles require more typically neutral
internal conditions, again relying on protective chemicals on or near their surfaces
or in their secretions to ensure the external environment is held at bay.
Diverse degradative abilities
Bacteria possessing pathways involved in the degradation of a number of organic
molecules of industrial importance, have been acknowledged for some time. One
oft-quoted example is that for toluene degradation in Pseudomonas putida ,which
exhibits a fascinating interplay between the genes carried on the chromosome and
the plasmids (Burlage, Hooper and Sayler 1989). Bacteria are constantly being
discovered which exhibit pathways involved in the degradation and synthesis of
chemicals of particular interest to environmental biotechnologists. For example, a
new class of biopolymer produced by the bacterium, Ralstonia eutropha , contain-
ing sulphur in its backbone, has recently been identified. (Lutke-Eversloh et al .
2001) It is possible that these and other novel biopolymers awaiting discovery,
will have innovative and exciting applications in clean technology.
In very recent years, bacteria representing very diverse degradative abilities
have been discovered in a variety of niches adding almost daily, to the pool of
organisms of potential use to environmental biotechnology. By illustration these
include phenol-degrading Oceanomas baumannii isolated from estuarine mud
from the mouth of the River Wear, UK (Brown, Sutcliffe and Cummings 2001),
chloromethane utilising Hyphomicrobium and Methylobacterium from polluted
soil near a petrochemical factory in Russia (McDonald et al . 2001) and a strain
of Clostridium able to degrade cellulose, isolated from soil under wood chips or
the forest floor in northeast USA. In addition to their cellulytic activity, these
Clostridia were also found to be mesophilic, nitrogen-fixing, spore-forming and
obligate anaerobes (Monserrate, Leschine and Canale-Parola 2001). Again, there
is interest in this organism with regard to clean technology in the hope that it may