Biomedical Engineering Reference
In-Depth Information
Research Needs: Basic Science - Ecosystem Scale
Understand the distribution of these organisms around the globe.
Where did they come from?
How do microbes and their catalytic activities spread to contaminated sites?
Need to develop practical combined remedies.
Chemical/Biological
Thermal/Biological
Need fully-instrumented field sites.
Similar to CFB Borden, Moffett Federal Airfield, and other sites.
Allow testing of hypotheses at field scale.
12.3 KEY CONCEPTS FOR BIOAUGMENTATION
RESEARCH
This section will consider some fundamental concepts for future bioaugmentation research
and development. Three concepts are discussed: the ecological niche, the value of microcosms
and the enrichment paradox. The thesis is that an improved understanding of these concepts
will foster innovation and lead to breakthroughs in the application of bioaugmentation.
12.3.1 The Niche Concept and Its Importance for Bioaugmentation
The word “niche” is derived from the Middle French word
nicher
, meaning
to nest
. The full
range of environmental conditions (biological and physical) under which any organism can exist
describes its fundamental niche. Ecologists further refine this definition considering the effects
of resource availability, competition and predation to define a realized niche that is narrower
than an organism's fundamental niche. Natural selection drives competing species into differ-
ent patterns of resource use, in other words into different niches. This process allows two
species to partition certain resources so that one species does not outcompete the other. The
result of prolonged competition and natural selection has created very narrowly defined niches
for some organisms.
Dehalococcoides
is a case in point. The following section explores what
this concept means for bioaugmentation.
12.3.1.1 Anaerobic Dehalogenation and
' Niche
Physiological and genomic analyses have confirmed that the
Dehalococcoides
niche is similar
to that of methanogenic Archaea from an electron donor and oxidation-reduction potential
(redox) perspective. Specifically, like most methanogens,
Dehalococcoides
have an obligate
requirement for highly reduced conditions, and require hydrogen as an electron donor. Hydrogen
is provided in nature by fermentation of a broad range of substrates, and therefore is not a
significant limitation in the ecological sense. However, from the electron acceptor perspective,
Dehalococcoides
are highly adapted to a very specific niche, as they can only use halogenated
organic substrates as terminal electron acceptors. This degree of specialization is remarkable, and
was quite unexpected. Now it seems probable that other dechlorinating organisms, including
Dehalobacter
and
Dehalogenimonas,
may have similarly restricted metabolisms.
Dehalococcoides
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