Unravelling adaptive evolution in response to changing salinities in a tripartite species interaction

• Main Author: Goehlich, Henry
• Format: Thesis
• Language: English
• Published: 2021
• Subjects: Ocean acidification
• Online Access: https://oceanrep.geomar.de/id/eprint/51984/; https://oceanrep.geomar.de/id/eprint/51984/1/20210101_PhDthesis_Henry_final.pdf; https://macau.uni-kiel.de/receive/macau_mods_00001160

Over a long time, marine organism have adapted to their biotic and abiotic environment. Currently, anthropogenic induced climate change is rapidly altering the environment with unpredictable consequences for marine ecosystems. To predict how organisms will cope with those changes in a future ocean, research mainly focused on exposing individual species to elevated water temperatures and ocean acidification scenarios. In the Baltic Sea, a decrease in salinity due to increased rainfall is predicted to be an additional stressor for marine life. However, the impact of low salinity levels on marine organisms has been ignored. By studying the interaction between a filamentous phage and an opportunistic bacterium (Vibrio alginolyticus) as well as the interaction between V. alginolyticus and the pipefish Syngnathus typhle, this thesis provides empirical data on the ecological and coevolutionary consequences of altered salinity levels on species interactions. Filamentous phages can infect and integrate in the genome of Vibrio bacteria. Whether filamentous phages are detrimental or beneficial for the bacterium depends not only on the costs they are causing for the bacterium, but also on the additional genes they are carrying and the environment. The genes introduced by the phage can provide the bacterium with additional properties which help the bacterium to infect marine animals. The results of chapter I, show that filamentous phages predominantly infect Vibrio bacteria within one clade. Infections and thus potential transfer of genes across bacterial clades occur at lower frequencies. In chapter II, I showed that reduced salinity levels made the bacteria more susceptible for phage infections, which may result in an increased transfer of genes between bacteria and facilitate the spread of virulence and antibiotic resistant genes in the future Baltic Sea. In chapter III, I used an evolution experiment to find out that Vibrio bacteria can quickly become resistant against filamentous phages and that resistance evolution is ...