>Magister Scientiae - MSc / Molecular methods were used to investigate the microbial diversity and community
structure of ammonia-oxidizing bacteria (AOB) associated with the roots of the
Proteaceae plant family. The identification of ammonia oxidizing bacteria in this
ecosystem is of particular interest since Proteaceae are adapted to acidic, low nutrient
(e.g. nitrogen) soils. The ammonia monooxygenase operon was used as a molecular
marker to identify ammonia-oxidizing bacteria associated with the proteoid roots of
the three Proteaceae members and compared to non-plant associated soil. PCR
amplification using primer sets targeting the ammonia monooxygenase gene (amoA
subunits) were used to construct a clone library. Sequence diversity was determined
by RFLP analysis of amoA to identify major groups of AOB of the ~-subclass of
Proteobacteria in total community DNA, and DNA sequencing and phylogenetic
analysis were also applied. DGGE analysis was performed to determine the
community structure and distribution of ammonia-oxidizing bacteria in plant-associated and non-plant associated soils. The AOB genotypic diversity was similar in
the plant-associated samples and non-plant associated soil. All AOB phylotypes
belonged to Nitrosospira species and clustered with Nitrosospira cluster 3. The
abundance of the amoA was quantified to be approximately 4.2 x 107 copies/g of dry
soil, using a real-time PCR assay. These data suggest that the Nitrosospira species are
the dominant phylotypes in that environment. This investigation provides new insights into
the relationships between plants and ammonia-oxidizing bacteria in natural Fynbos
ecosystems.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uwc/oai:etd.uwc.ac.za:11394/8831 |
| Date | January 2005 |
| Contributors | Cowan, D. A. |
| Publisher | University of the Western Cape |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Rights | University of the Western Cape |
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