engleski

Isolation and molecular characterization of endosymbiotic alga from green hydra

Symbiotic associations are of a wide significance in evolution and biodiversity. The green hydra is a typical example of endosymbiosis. In its gastrodermal myoepithelial cells it harbors the individuals of a unicellular green algae. Thus far it has been accepted that endosymbiotic algae from green hydra are impossible to grow in a clean lab culture. Hydras were collected on two distant localities in Zagreb, Croatia: Jarun Lake (strain S1J - J1) and the greenhouse of the Botanical gardens (strain S1B - S1) from the surface of submersed plants, and maintained in lab cultures. In this study endosymbiotic algae from green hydra have been successfully isolated and permanently maintained in a stable clean lab culture on a sterile deep stock agar in tubes by means of microbiological methods. We reconstructed the phylogeny of endosymbiotic algae using the 18S rRNA gene, which is unavoidably used in the phylogeny of symbiotic organisms as essential molecular marker which evolves slowly and is functionally preserved, to clarify its current status and to validate the traditional inclusion of these endosymbiotic algae within the Chlorella genus. Molecular analyses (Bayesian analysis, Maximum likelihood, Maximum parsimony) established that different genera and species of unicellular green algae could be present as symbionts in green hydra, depending on the natural habitat of a particular strain of green hydra. The results showed that the isolated endosymbionts belonged to the genera Desmodesmus and Mychonastes. The green hydra symbiosis revealed that hydra-alga associations’ biodiversity is much more complex than previously thought.

endosymbiosis ; green hydra ; alga ; phylogeny

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