Novel active kinetoplastids associated with hypersaline anoxic basins in the Eastern Mediterranean deep-sea

The combination of nearly saturated salt concentration and corresponding high density, high hydrostatic pressure, absence of light, anoxia, and a sharp chemocline make the deep hypersaline anoxic basins in the Eastern Mediterranean Sea some of the most polyextreme habitats on Earth. Using kinetoplastid-specific primers, we detected kinetoplastid flagellates in some of the harshest deep-sea environments known to date, including some whose small subunit ribosomal RNA gene sequences are not closely related to cultured representatives. Kinetoplastids, including presumably novel representatives appear to be specialists of halocline environments in the Eastern Mediterranean, and to comprise a significant fraction of the protist communities in the brines and haloclines of several basins. Fluorescent in situ hybridization data indicate a novel ‘unidentified’ sequence clade of kinetoplastids related to bodonids represents as much as 10% of the total protist community in the Discovery Basin halocline. Different kinetoplastid groups are unevenly represented in the different basins and habitats we sampled, which we discuss as a result of environmental selection.

► Deep hypersaline anoxic lakes in Eastern Mediterranean are some of the most polyextreme habitats on Earth.
► First combo of FISH and rRNA data show active protists in the halocline and/or brines of some basins.
► Distinct chemical compositions of brine lakes select for different lineages of kinetoplastids.
► Kinetoplastid flagellates are significant members of the microbial eukaryote community.
► Novel clade of kinetoplastids represents up to 10% of  protists in some DHAL habitats.