@PhdThesis{macau_mods_00000591,
  author = 	{Bathia, Jay},
  title = 	{Tripartite symbiosis in Hydra viridissima: Understanding the interactions between host, algae and bacteria},
  year = 	{2020},
  publisher = 	{Christian-Albrechts-Universit{\"a}t zu Kiel},
  address = 	{Kiel},
  keywords = 	{metaorganism; microbiome; causation; hydra},
  abstract = 	{The aim of the project was to understand the symbiotic interactions in Hydra viridissima metaorganism. The bipartite interaction between the host and the algae has been a subject of interest for decades, but the influence of bacteria on these interactions has always been overlooked. The first part of the thesis focused on expanding the understanding of the metabolic co-dependence between the host and the algae. Presented in chapter1, I showed the specificity of the metabolic genes in the host that aided in producing glutamine for the algae. Moreover, I could show that maltose, the photosynthetic sugar supplemented by the algae, was likely to be broken down into glucose before being utilized by the host. In the second part of this thesis, I expanded the view on symbiotic interactions in Hydra viridissima by taking the bacterial colonizers into consideration. Chapter 2.1 focuses on understanding the effect of algal symbionts on the bacterial composition. I could demonstrate that co-cultivation of symbiotic (hosts with algae) and aposymbiotic (hosts without algae) animals resulted in the transfer of an invasive bacterium Legionella sp. to the symbiotic animals. This bacterium was fitness costly for the host; it reduced the growth rate of the host and increased algal expulsion. These expelled algae were further taken up by the aposymbiotic animals. However, under the influence of algal photosynthesis, this bacterium was eventually lost from the population, thus portraying the role of algae in controlling the invasive species and maintaining the core microbiome of the host. Chapter 2.2 focuses on the effect of bacterial symbionts on the host and algal fitness. I assessed a wide array of fitness parameters and compared the germ-free (bacteria-free) symbiotic and aposymbiotic animals with the respective controls to study if there is any fitness loss in the absence of bacteria. Since the results were not conclusive and I could not observe any detectable effect of the bacteria, I replaced the native bacteria with complete sets of bacterial consortia from other Hydra species and assessed for their impact on host fitness. Interestingly, I could see reduced fitness in all animals that received foreign bacteria, thus portraying the importance of harboring the native, stable microbiota.},
  url = 	{https://macau.uni-kiel.de/receive/macau_mods_00000591},
  file = 	{:https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/macau_derivate_00001620/Jay_Bathia_thesis.pdf:PDF},
  language = 	{en}
}