The Hydra Holobiont: A Tale of Several Symbiotic Lineages
The personal journey of one of us (TB) toward the realization that beneficial microbes are important began in summer 2000 when Jens Schröder, a dermatologist at Kiel University, on the occasion of the inauguration of the new chair of Zoology asked if Hydr
- PDF / 950,215 Bytes
- 19 Pages / 439.37 x 666.14 pts Page_size
- 90 Downloads / 211 Views
The Hydra Holobiont: A Tale of Several Symbiotic Lineages
The personal journey of one of us (TB) toward the realization that beneficial microbes are important began in summer 2000 when Jens Schröder, a dermatologist at Kiel University, on the occasion of the inauguration of the new chair of Zoology asked if Hydra were not a good model system to investigate the biochemistry of epithelial defenses. Nobody at that time would have anticipated that this triggered the development of a novel model system in comparative and evolutionary immunology. Up to that moment, Hydra was all for examining developmental mechanisms in an evolutionary context and to uncover basic principles of pattern formation and stem cell regulation. To think of immune reactions as equally important features of an animal did not come to our mind. That evolution of a simple multicellular animal such as Hydra means both invention of developmental pathways to shape and maintain a given body plan and also to protect this body all life long, and understanding that part of that context requires understanding the biotic and abiotic environment in which Hydra evolved turned out to be enlightening and exciting. This chapter will show just how much we know about host–microbe interactions in Hydra and what these findings mean in a more general context of holobiont research. Hydra represents a classical model organism in developmental biology which was introduced by Abraham Trembley as early as 1744 (Fig. 7.1). Because of its simple body plan, having only two epithelial layer (an endodermal and ectodermal epithelium separated by an extracellular matrix termed mesoglea); a single body axis with a head, gastric region, and foot; and a limited number of different cell types, Hydra served for many years as model in developmental biology to approach basic mechanisms underlying de novo pattern formation, regeneration, and cell differentiation.
© Springer-Verlag Wien 2016 T.C.G. Bosch, D.J. Miller, The Holobiont Imperative: Perspectives from Early Emerging Animals, DOI 10.1007/978-3-7091-1896-2_7
79
80
7.1
7 The Hydra Holobiont: A Tale of Several Symbiotic Lineages
Rationale for Studying Host–Microbe Interactions in Hydra
Novel computational tools and genomic resources have brought a molecular perspective on the Hydra holobiont. The genome sequence of Hydra magnipapillata revealed an unexpectedly high genetic complexity. In the sequencing process, we accidentally also sequenced the genome of a bacterial species in the Curvibacter genus that is stably associated with Hydra. The Hydra magnipapillata genome is large (1290 M base pairs in size) and contains approximately 20,000 protein-coding genes (Chapman et al. 2010). We found clear evidence for conserved genome structure between Hydra and other animals including humans. This contrasts with organisms such as Drosophila and the worm C. elegans where gene order has been shuffled extensively during evolution. In spite of the fact, however, that Hydra belongs to one of the phylogenetically oldest eumetazoan lineage
Data Loading...
