Environmental Engineering Reference
In-Depth Information
the contaminant. The second phenomenon is of
great interest as it increases the bioavailability of
a pollutant to bacteria. As heavy metals are com-
mon contaminants worldwide and are a threat to
the quality and sustainability of natural soil re-
source, rescuing of the heavy metal contaminated
soils by microbes (in situ bioremediation) is a low
cost and effective tool to minimize environment
pollution and is in use today. Evdokimova (
2000
)
have shown that in copper, nickel, cobalt, and
sulphur compound contaminated sites in Kola
Peninsula, the microbial diversity decreased a
lot. But the fungi, bacteria, and actinomycetes
were found to bioconcentrate these heavy metals
by volatilizing or accumulating in cell capsules
etc.
P. flourescens
AF39 accumulated heavy met-
als such as nickel and others and the whole pro-
cess was observed to be rapid and pH dependent.
Several biomarkers or technically biosensors are
available now to obtain the presence of specific
contaminant at a particular site.
a chemical synthesis. Remarkable milestone in
the medicinal use of microbial metabolites and
their derivatives was the introduction of the im-
mune suppressants cyclosporin A, and rapamycin
(Chen et al.
1995
, Van Middlesworth and Cannell
1998
). Other examples are the commercialization
of the antihyperlipidemic lovastatin and gug-
gulsterone (Urizar et al.
2002
). Microbial natural
products have also been developed as antidiabet-
ic drugs, hormone (ion-channel or receptor) an-
tagonists, anticancer drugs, and agricultural and
pharmaceutical agents (Zhang
2005
).
4.5
Genetic Diversity
and Metagenomics
Genetic diversity is manifested as biological di-
versity through the structure, organization, regu-
lation, and expression of DNA. Presence and
expression of DNA in the biological systems of
a given environment determine the physiological
functions of the biotic and abiotic components of
the environment. Metagenomics (also referred
to as environmental and community genomics)
is the genomic analysis of microorganisms by
direct extraction and cloning of DNA from an
assemblage of microorganisms. It is a new field
combining molecular biology and genetics to iso-
late, identify, and characterize the genetic mate-
rial from environmental samples and express it in
suitable host. The metagenomic DNA is inserted
into a model organism that lacks a specific gene
function. Restoration of a physical or chemical
phenotype can then be used to detect genes of in-
terest. A genotype is the specific sequence of the
DNA and offers another means of analyzing the
metagenomic DNA fragment. The sequences of
the bases in DNA can be compared to the data-
base of known DNA to get information regard-
ing the structure and organization of the metage-
nomic DNA. Comparisons of these sequences
can provide insight into how the gene proteins
function.
4.4.4
Microbial Products Used in
Novel Chemical Synthesis
Bioprocesses, which involve biocatalysts for the
production of useful compounds, are expected to
play a key role in green chemistry. Microbial di-
versity constitutes an infinite pool of novel chem-
istry, making up a valuable source for innovative
biotechnology. So far we have only scratched the
surface of it. The most recent estimates suggest
that by now we only know approximately 5 % of
the total species of fungi and may be as little as
0.1 % of the bacteria and among the ones already
described, only a small fraction has been exam-
ined for metabolite profile.
The microbial secondary metabolites can be
brought in use in three different ways: the bio-
active molecule can be produced directly by fer-
mentation; or the fermentation product can be
used as starting material for subsequent chemi-
cal modification (derivatization); or thirdly the
molecules can be used as lead compounds for
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