Diversity and distribution of eukaryotic microbes in and around a brine pool adjacent to the Thuwal cold seeps in the Red Sea

Abstract

A hypoxic/suboxic brine pool at a depth of about 850 m was discovered near the Thuwal cold seeps in the Red Sea. Filled with high concentrations of hydrogen sulfide and ammonia, such a brine pool might limit the spread of eukaryotic organisms. Here, we compared the communities of the eukaryotic microbes in a microbial mat, sediments and water samples distributed in 7 sites within and adjacent to the brine pool. Taxonomic classification of the pyrosequenced 18S rRNA amplicon reads showed that fungi highly similar to the species identified along the Arabic coast were almost ubiquitous in the water and sediment samples, supporting their wide distribution in various environments. The microbial mat displayed the highest species diversity and contained grazers and a considerable percentage of unclassified species. Phylogeny-based methods revealed novel lineages representing a majority of the reads from the interface between the sea water and brine pool. Phylogenetic relationships with more reference sequences suggest that the lineages were affiliated with novel Alveolata and Euglenozoa inhabiting the interface where chemosynthetic prokaryotes are highly proliferative due to the strong chemocline and halocline. The brine sediments harbored abundant species highly similar to invertebrate gregarine parasites identified in different oxygen-depleted sediments. Therefore, the present findings support the uniqueness of some microbial eukaryotic groups in this cold seep brine system.

Draft genome of an Aerophobetes bacterium reveals a facultative lifestyle in deep-sea anaerobic sediments

“…The Thuwal cold seep was discovered on the continental slope of the Red Sea. The seeping brine from this cold seep contains high concentrations of ammonia and H 2 S [26,43], but no methane. In the present study, we obtained a sediment sample under a microbial mat in the Thuwal cold seep and binned the draft genome of Aerophobetes TCS1 from the metagenome.…”

“…Minor components included halite (10.7 %) and quartz (2.9 %). The chemical components of pore water in the sediments near the cold seeps had been measured in our previous study [26], which indicates an anoxic and ammonia-rich environment in the sediment.…”

Diversity and Evolutionary History of the Symbiontida (Euglenozoa)

“…Although the specific taxonomic identities of these euglenozoans remain unknown, many of them are likely members of the Symbiontida. Environmental SSU rDNA sequence surveys suggest that members of the Symbiontida have a cosmopolitan distribution: Northern Europe (Framvaren Fjord, Norway; Mariager Fjord, Denmark), Western North America (Saanich inlet, Canada), Black Sea, Caribbean sea (Cariaco basin) and the Red Sea (Zuendorf et al, 2006;Orsi et al, 2011Orsi et al, , 2012Wang et al, 2014). The previous molecular phylogenetic analyses of eDNA sequences demonstrated three distinct symbiontid clades (A, B, and C) as well as a "putative novel euglenozoan class;" (Orsi et al, 2011).…”

“…Symbiontid clades A and B only contained sequences from the Cariaco basin (Venezuela), and symbiontid clade C contained sequences from the Framvaren and Mariager Fjords. Environmental DNA sequences closely related to Bihospites baccati were found near a cold seep 850 m deep in the Red Sea (Wang et al, 2014).…”

Changing composition of microbial communities indicates seepage fluid difference of the Thuwal Seeps in the Red Sea

“…These cold seeps consist of several seeping vents located on the seafloor of the Red Sea at a depth of approximately 850 m, where hypersaline brine seeps out of the seabed and fills an adjacent brine pool (Batang et al 2012). In a previous study, we characterized the eukaryotic microbial communities in this cold seep ecosystem and identified some lineages affiliated with novel Alveolata and Euglenozoa (Wang et al 2014b). In a previous study, we characterized the eukaryotic microbial communities in this cold seep ecosystem and identified some lineages affiliated with novel Alveolata and Euglenozoa (Wang et al 2014b).…”