Biomedical Engineering Reference
In-Depth Information
Examples of such mobility are viruses which infect a wide host range, such as
some retroviruses, the alfalfa mosaic virus and the Ti plasmid of
Agrobacterium
tumefaciens
which the bacterium introduces into plant cells. The retroviruses,
of which Human Immunodeficiency Virus (HIV) is an example, are unusual in
having RNA as their genetic material. They replicate in a manner which includes
double stranded DNA as an intermediate and so may integrate into the host cell
genome. RNA viruses tend to be more susceptible than DNA viruses to mutation
presumably due to the less chemically stable nature of the macromolecule. They
have been invoked as being the likely agents for the spread of genetic informa-
tion between unrelated eukaryotes by Reanney (1976). His observations led him
to conclude that there is only a blurred distinction between cellular and ECE
DNA both in eukaryotes and prokaryotes and further suggests that no organism
lives in true genetic isolation as long as it is susceptible to at least one of the
classes of ECEs described above. Clearly, for the mutation to be stabilised, it
must occur in inheritable DNA sequences, a situation reasonably easy to achieve
in microbes and at least possible in multicellular organisms.
The existence of genetic mobility has been accepted for many years, even
though the extent and the mechanisms by which it operates are still being elu-
cidated. From this knowledge several lessons may be learned; among them, that
the genetic environment of any organism may well be significant and that there
is some justification in viewing the principle of genetic engineering as perform-
ing in the laboratory, a process which is occurring in abundance throughout the
living world. This is a topic, that is further explored in later chapters.
Closing Remarks
As has been seen, even within the brief discussion in this chapter, life on Earth
is a richly varied resource and the functional reality of biodiversity is that many
more metabolic pathways exist, particularly within the microbial melting pot,
than might be commonly supposed. As a result, a number of generally unfamil-
iar groups of chemicals and organisms have implications for the application of
environmental biotechnology which exceed their most obvious contributions to
a wider consideration of the life sciences. Hence, xenobiotics, as an example of
the former, represent a current problem for which the solution remains largely
unresolved and extremophiles, as the latter, hold the potential to revolutionise
many industrial procedures, thereby heralding major benefits in terms of 'clean
technology'. There are many aspects of current environmental management for
which there is no presently relevant biotechnological intervention. However, this
is not a static science, either in terms of what can be done, or the tools available.
Thus, while the bulk of the rest of this topic addresses the sorts of biotechnolog-
ical applications that have now become fairly routinely applied to environmental
problems, discoveries and developments both within the field and from other
disciplines can and do filter in and alter the state of the possible.
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