Search

Erwinia amylovora can rapidly become highly resistant to applications of the antibiotic streptomycin through a single nucleotide mutation in the rpsL gene, which causes an amino acid substitution that prevents inhibitory binding of streptomycin while preserving the functionality of the ribosome. Several viable mutations are described in the literature, but screenings in the orchards consistently revealed that the one leading to the substitution of lysin by arginine at position 43 (K43R) is by far the most abundant. In this work, we tested the rate of emergence of the various spontaneous mutants, their tolerance to different antibiotic concentrations and their general fitness in competition experiments. Furthermore, we developed a molecular assay based on the SNaPshot™ Multiplex Kit from Thermo Fisher Scientific that allows swift determination of rpsL mutations using a single-base primer extension approach directly from colonies on plate. Or results indicate that the prevalence of variant K43R is largely due to fact that it retains the highest environmental fitness even in absence of antibiotic pressure. Sequence analysis of two resistant colonies that did not respond as expected in the SNaPshot™ assay revealed the existence of two yet undescribed rpsL mutations resulting in conditional-lethal streptomycin-dependent (SmD) phenotypes, which are unable to grow in absence of the antibiotic.

Natural floodplains belong to ecosystems with the highest biodiversity. Human use of water, for instance to produce energy, affects the amount of water which is present in the river. This, affects the ecology of the water body and the adjacent floodplains. Therefore, there are negative effects on the diversity of habitats and on the biodiversity of the floodplains. Achieving a natural regime is an important factor in the revitalisation of regulated rivers. Since floods are an important characteristic of a natural regime of a river, experimental floods are being increasingly used to minimise the negative effects of river and storage power plants. As part of the National Research Program "energy revolution" (NFP70), on the 14. and the 15. of September 2016 an experimental flood (eFlow) was released at the Rossens dam into the Sarine river. The impacts on microbiology and abiotic parameters in different habitats of the floodplain that were studied for this thesis are based on the aforementioned eFlow., Natürliche Auenlandschaften gehören, durch die Diversität ihrer Lebensräume, zu den Ökosystemen mit der höchsten Biodiversität. Die menschliche Nutzung der Gewässer, unter anderem für die Erzeugung von Energie, beeinflusst die vorhandene Wassermenge und wirkt sich somit auf die Ökologie des Gewässers und die angrenzenden Auenlandschaften aus, was negative Einflüsse auf die Diversität der Lebensräume und somit auf die Biodiversität der Auenlandschaften hat. Das Erreichen eines natürlichen Abflussregimes ist ein wichtiger Faktor in der Revitalisierung von regulierten Flüssen. Da Fluten wichtige Eigenschaften eines natürlichen Abflussregimes von unbeeinträchtigten Fliessgewässern darstellen, werden vermehrt experimentelle Fluten zur Minimierung der negativen Auswirkungen von Fluss- und Speicherkraftwerken eingesetzt, da durch diese das natürliche Abwasserregime simuliert werden kann. Im Rahmen des Nationalen Forschungsprogramms „Energiewende“ (NFP70) wurde am 14. und 15. September 2016 eine experimentelle Überflutung (eFlow) beim Rossens Stausee an der Saane durchgeführt. Anhand dieser eFlow wurde in dieser Bachelorarbeit der Einfluss auf die Mikrobiologie und abiotische Parameter in verschiedenen Habitaten der Flussaue untersucht.