Protistan life in deep hypersaline anoxic basins in the eastern Mediterranean Sea
Final Report Abstract
The goal of the conducted project was the exploration of protistan life in the brines of geochemically contrasting hypersaline anoxic deep-sea basins (DHABs) located in the eastern Mediterranean Sea, which belong to the most polyextreme habitats known on our planet. Genetic signatures (SSU rRNA genes) suggested the existence of unexpectedly rich and diverse plankton communities in the DHABs. Most of these signatures were highly divergent to known sequences deposited in public databases, pointing to a high degree of taxonomic novelty existing in the DHABs. Subsequent fluorescence in situ hybridization analyses with fluorochromelabelled oligonucleotide probes (FISH) succeeded to microscopically visualize some of the taxa, confirming this high degree of taxonomic novelty as well as the true existence of these taxa in the DHABs. This finding redefines the limits of eukaryote life under extremely low water activity. An in-depth analyses of the plankton communities in the basins L’Atalante, Tyro, Medee, Thetis, Bannock, Urania and Discovery, all of which are characterized by different physicochemical environmental settings, using terminal restriction fragment lengths polymorphism and next generation sequencing technologies revealed a specific partitioning of the diversity patterns. Statistical analyses identified the type of salt, its concentration, and also sulphides explain as variables that explain a large proportion of the observed diversity patterns. Distance-decay relationships could not be detected. Based on these data, we developed a scenario, in which the evolutionary history of the basins as well as environmental settings are made responsible for the spatial distribution of the distinct polyextremophile plankton communities. Current efforts are in order to identify the physiological potential of the individual DHAB plankton communities. This will help to understanding the selective force of environmental parameters in shaping the DHAB plankton communities and their distribution patterns. Two major articles in a newspaper (Rheinpfalz) reported from this project. Furthermore, this project was invited for an article in the DFG magazine “forschung”. For one of our research cruises we had a webpage through which we communicated with local schools.
Publications
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(2009) Protistan community patterns within the brine and halocline of deep hypersaline anoxic basins in the eastern Mediterranean Sea. Extremophiles 13:151-167
Edgcomb V, Orsi W, Leslin C, Epstein Ss, Bunge J, Jeon S, Yakimov Mm, Behnke A, Stoeck T
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(2011) Novel active kinetoplastids associated with hypersaline anoxic lakes in the eastern Mediterranean deep-sea. Deep Sea Res Part I, 58: 1040-1048
Edgcomb V, Orsi W, Breiner HW, Stock A, Filker S, Yakimov MM, Stoeck T
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(2012) Unveiling microbial life of new deep-sea hypersaline lake Thetis. Part II: Microeukaryotes. Extremophiles 16:21-34
Stock, Breiner, Pachiadaki, Edgcomb, Filker, La Cono, Yakimov, Stoeck
