Microorganisms are fundamental components of many geochemical transformations
occurring in the aquatic environment. Microbial redox and methylation of metals within
the environment can alter metal speciation, mobility and ultimately, toxicity to
eukaryotes. It is therefore practical that any environmental monitoring framework
advocating the application of `early-warning biomarker system' should incorporate a
holistic view of the environment beginning with microbial activity. This thesis describes
the development of protocols for assessing the in situ condition of microbial ecosystems
within a gradient of metal contaminated sites radiating downstream of the Anaconda
Smelter, a USEPA-designated superfund site and within two control sites. Experiments
focus on evaluating the incidence (i. e. prevalence and absence) of genes related to
general stress and specific metal detoxification reactions. Moreover, a number of
selected genes were quantified directly from the environment and statistically correlated
with metal concentrations. Furthermore, the influence of metals on structuring microbial
communities was also investigated by evaluating temporal communities shifts in response
to changing metal concentrations using denaturant gradient gel electrophoresis (DGGE).
The data recorded the highest prevalence of all genes was found at the most polluted site
directly downstream of the Anaconda Smelter. Furthermore, significant correlations
were observed between gene prevalence and metals (arsenic, copper and zinc) (P < 0.05)
and organic carbon concentration (P < 0.05). A number of genes were successfully
amplified from sediment with significantly higher gene copy number (/ ng DNA) at the
more polluted sites when compared to corresponding control sites. Examination of
community diversity found that long-term metal-contaminated sediments, adjacent to the
Smelter, had microbial communities twice as diverse as corresponding reference sites. In
addition, multivariate statistical techniques identified factors important to community
structuring, concluding that geographic position and localized geochemistry
fundamentally influence the structuring of communities. This thesis represents a
significant advance in the use of microorganisms as `early warning systems' of
deterioration in ecosystem health, while the application of advanced molecular methods
facilitates their intergration within a traditional ecotoxicological framework.
Date of Award | 2006 |
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Original language | English |
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Awarding Institution | |
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The development and optimization of microbial molecular biomarkers for the in situ assessment of trace metal toxicity
Bouskill, N. J. (Author). 2006
Student thesis: PhD