Insights into the Holobiont of the Early Branching Metazoan Vaceletia sp. and its Biomineralization Strategy
by Juliane Germer
Date of Examination:2017-09-13
Date of issue:2017-12-05
Advisor:Prof. Dr. Daniel John Jackson
Referee:Prof. Dr. Daniel John Jackson
Referee:Prof. Dr. Joachim Reitner
Persistent Address:
http://dx.doi.org/10.53846/goediss-6604
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Abstract
English
Sponges are evolutionary and ecologically very successful animals. They are abundant and significant members of benthic communities throughout the world’s oceans. Having emerged during the Neoproterozoic era, sponges are among the most ancient of all extant animal lineages. Due to this basal branching position sponges are ideal models to gain insights into the origin and evolution of important metazoan traits. This thesis addresses two important aspects of sponge biology. The first part focuses on host-microbe interactions of the hypercalcifying demosponge Vaceletia sp. Like Vaceletia, most sponges comprise dense and diverse microbial communities that can constitute up to 50% of the sponge’s biomass. The analysis and characterization of Vaceletia sp. holo-transcriptome, and the comparison to other sponge transcriptomes and genomes shows that this sponge interacts in various ways with its microbial community. The results of my study imply that the sponge immune system as well as eukaryotic–like proteins from bacteria play an important role in mediating interactions. By studying the underlying molecular mechanisms of lipid pathway components, I showed that short chain fatty acids and midchain branched fatty acids are most likely produced by the sponge’s bacterial community, whereas long chain fatty acids are most likely synthesized by the sponge itself via elongation and desaturation of short-chain precursors. The second part of this thesis focuses on the biomineralization strategy employed by Vaceletia sp. By generating a comprehensive skeletal proteome of this sponge, I identified and characterized 40 proteins that most likely represent the majority of components playing an important role in the mineralization process of Vaceletia. The proteome contains components showing similarities to already identified proteins with a known role in biomineralization as well as novel components. The microbial community of Vaceletia sp. apparently plays a minimal role in directly contributing proteinaceous compounds to the skeleton formation in this sponge. This thesis represents the first investigation into the molecular mechanisms underlying sponge-microbe interactions and the biomineralization of the early branching Vaceletia sp. The studied interactions include innate immunity, eukaryotic-like proteins in bacteria and metabolic interactions. The results of my thesis expand our knowledge of the complex gene repertoire of sponges, show the importance of metabolic interactions between Vaceletia and its microbial community, and give insight into the biomineralization strategy of this sponge.
Keywords: biomineralization; sponge; microbes; symbiosis; transcriptome; metabolism; fatty acids; immunity; signalling pathway; extracellular matrix; proteome