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Gewählte Doctoral Thesis:

Melanie Kuffner (2007): Identification of specific interactions between bacteria and heavy metal accumulating plants.
Doctoral Thesis, BOKU-Universität für Bodenkultur, pp 120. UB BOKU obvsg FullText

Data Source: ZID Abstracts
Various plants growing on metalliferous soils accumulate metals and can be used to remove heavy metals from polluted soils. Plant-associated bacteria contribute to the accumulation process. The objectives of this work were the characterization of bacteria associated with Zn/Cd accumulating Salix caprea trees, the identification of strains promoting metal accumulation and the elucidation of interaction mechanisms between bacteria and heavy metal accumulating plants. Rhizosphere isolates and endophytes from Salix caprea were screened for production of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, indole-3-acetic acid (IAA), siderophores and other metal mobilizing compounds, because these substances are thought to increase heavy metal uptake and tolerance in plants. IAA, ACC deaminase and siderophore production were detected in many isolates. Individual strains mobilized high amounts of Zn, Cd and Fe. Inoculation experiments with Salix caprea plantlets identified a Streptomyces strain enhancing Zn and Cd uptake and an Agromyces promoting plant growth. These bacteria did not produce siderophores, ACC deaminase or IAA, highlighting the importance of novel interaction mechanisms. To identify genes involved in such novel mechanisms, a Methylobacterium isolate from the Ni hyperaccumulator Thlaspi goesingense was searched by suppression subtractive hybridization (SSH) for sequences that distinguish this strain from close relatives with different habitats. The identified sequences showed similarity to DNA methylases, metabolic genes, cell surface proteins and regulators or were not related to any described gene. Further plant experiments are required to reveal which of the described phenotypic characteristics and novel genetic traits are the most relevant and to develop techniques for the stimulation of beneficial plant-microbe interactions in phytoremediation systems.

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