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Hydra Glue: Bioadhesion of a freshwater polyp

Final Report Summary - HYDRAGLUE (Hydra Glue: Bioadhesion of a freshwater polyp)

The capability of attachment, either temporary or permanent, of an organism to a surface is referred to as “Bioadhesion”. Bioadhesion occurs in many organisms, ranging from microscopic, such as bacteria, through much larger and complex marine algae, invertebrates, and terrestrial vertebrates. By providing information on how animals solve problems of adherence in diverse environments, such a subject offers models for bio-inspired technology with major applicability in the fields of surface engineering, and biomedicine. Recent advances in biotechnology have made available a wide range of applicable research tools and techniques, but our knowledge of natural adhesive systems remains distant from the engineering of innovative adhesives for specific industrial, and medical needs. Although initially found in traditional research on histology, biochemistry and mechanics, bioadhesion is little by little entering the genomic and proteomic era by appearing in complex functional studies. Taking into account that efforts to develop bioadhesives are most effective when guided by a detailed understanding of the key features and mechanisms of natural adhesives, in this project was intended to use cutting-edge methods in molecular biology and protein identification techniques to explore the mechanism by which the freshwater cnidarian Hydra (Cnidaria, Hydridae) adheres to the substrate.

The HydraGlue project started work in 2014 funded by the European Commission as a Marie-Curie Individual Intra-European Fellowship (IEF). The project was led by the University of Innsbruck (Austria), and counted with one national and two international research partners.
• University of Innsbruck (Coordinator and host)
• Medical University Innsbruck
• University of Mons
• University of Groningen
This team was specifically set up to provide the necessary combination of expertise in molecular and animal biology, immunochemistry, proteomics, and bioinformatics to ensure interdisciplinary training to post-doctoral researcher (Dr. Marcelo Rodrigues). The key research objective was to study the molecular mechanism involved in the underwater attachment of the freshwater cnidarian Hydra, and to discover the sequences of adhesive-protein precursors to develop novel adhesives that mimics its function in nature. In particular the project focused on the basic morphological and molecular components that facilitate organismic adhesion to the underwater surface. Our vision is that this enhanced understanding will inform the future development of new mimetic adhesives. The fellow was trained in the above mentioned thematic areas through a range of interdisciplinary projects, training courses, and short-term research visit to cooperation partners. The fellow involvement in a funded COST Action on biological adhesives (TD0906), and participation in EMBO funded courses, provided important training in a range of transferable and generic skills to enhance the future career prospects of the training fellow in academia or industry.
A range of advanced techniques such as electron, super-resolution, and atomic force microscopy, histochemistry, and immunolabelling were used to characterize the basic of cellular components involved in Hydra adhesion. Then RNA sequencing, a range of molecular biology and proteomic tools, and mass spectrometry were used to identify candidate genes involved in the adhesive mechanism. The functionality of the candidate genes are currently underway and it is expected that some of the candidate genes have an ultimate function in the organismic adhesion mechanism.

• This project showed that cnidarian Hydra polyps secrete elaborate adhesive composites underwater (freshwater) to temporarily anchor themselves to substrate surfaces. The adhesive components of Hydra are produced, stored and delivered by a single cell type, the ectodermal basal disc cells, something unique in the animal kingdom.
• The adhesive system used by Hydra exhibits unique features among metazoans. Proteinaceous glue based adhesion is the main component of the system: basal disc cells release their adhesive vesicles whose contents would have the ability to spread over the surface, displace water, and create a proper environment for curing the secreted glue.
• Post-translational modifications such as glycosylation offer additional physico-chemical properties to the adhesive and seems to be a crucial component of the system. It was elucidated at both gene and histochemical level.
• As many as 21 proteins were found that maybe structural components of or be involved in processing the secreted adhesive.

Advances in the development of novel ‘bioinspired’ adhesives, nanotechnology, and polymer science will help us to understand better the structure/properties relationship of a bioadhesives in nature, and their biological performance in silico as well. That understanding can be further enhanced by knowledge of the biointerfacial processes involved in adhesion, including how organisms explore different surfaces, the interrelationships between different organisms phylogenetically related but environmentally distant (ex. freshwater vs saltwater), and the nature of the bioadhesives themselves. Taken together this understanding will inform the development of a new generation of environmentally-friendly adhesives that have the potential of, i) to reduce the use of fossil fuels based adhesives and therefore greenhouse-gas emissions, and to reduce the release of harmful substances into the environment; ii) will favour the development of bioadhesives that outperform the current developments, mainly in the biomedicine, packaging and furniture industries.