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Nature manuscript. Life in Deep-Sea Hypersaline Anoxic Basins. Objectives. What determines the establishment of microbial communities in the different DHABs? What are the functional and biogeochemical relationships in the four DHABs?

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Nature manuscript

Life in Deep-Sea Hypersaline Anoxic Basins


Objectives

  • What determines the establishment of microbial communities in the different DHABs?

  • What are the functional and biogeochemical relationships in the four DHABs?

  • Is there life under the extreme conditions of the Discovery basin?


Methods

  • 16S rDNA analysis:

    • Clone libraries (Paul/Henk)

    • t-RFLP (Terry/Andrea)

    • ARISA, DGGE (Sara/Daniele)

  • Enzyme activities:

    • SO4 reduction rates, CH4 production (Daniëlle)

    • Glutamate respiration and assimilation, Aminopept. and phosphatase activity (Christian)

  • Meiofauna data (Nikos/Elena/Tassos)

  • Geochemical data

    • Na, Cl, Mg, K, Ca, HS, SO4 (Andreas/Gert)

    • Ba, Ni, Cu, Pb, Si, Mn Cr, Fe, Cd, Sr, Al (Soteris)

    • Sediment accumulation rates (John)

    • CH4 (Daniëlle)


  • Objective 1. Establishment microbial community

    UPGMA cluster analysis 16S rDNA sequence data (Bacteria and Archaea)

    UPGMA cluster analysis geochemical data


    Objective 1. Establishment microbial community

    • Both cluster analyses show the same clustering of the different DHABs

    • Geochemical conditions in the brines thus correlates to the differences in microbial communities

    • To be included: meiofauna data??, fingerprinting data??


    Objective 2. Functional and biogeochemical relations

    Table 3. Enzymatic activities, CH4 production and sulfate reduction rates in brine waters of the four different DHABs.


    Objective 2. Functional and biogeochemical relations

    16S rDNA data

    • Sulfate reducing and sulfide oxidizing bacteria present in brines and interfaces.

    • Dominant archaea in brines belong to a new subdivision in the archaea tree (MSBL1).

    • Sphingobacteria, Planctomycetales, α-, γ-proteobacteria, Firmicutes, Verrucomicrobiae, Actinobacteria, Chloroflexi, Acidobacteria and Halobacteria are present in brines and interfaces thus (fermentative) heterotrophic bacteria/archaea are important as well.


    Objective 2. Functional and biogeochemical relations

    • Sulfate reduction, sulfide oxidation and heterotrophic metabolic routes are important in brines and interfaces.

    • No clear results about methanogenesis. Natural methane production measured but only few sequences related to methanogenic archaea. However, most archaeal sequences unknown.

    • Anaerobic methane oxidation. No results showing that this occurs in the brines. If we want to include this in future studies we need to measure δ-13C values to my opinion.

    • To be included: meiofauna???


    Objective 3. Life in Discovery?

    Table. Morisita-Horn index for similarity between OTU distribution of Discovery brine and interface water and seawater at 3300 meters depth just above Discovery brine.


    DW1500

    DW2500

    DW3300

    DI

    DB

    Objective 3. Life in Discovery?

    Figure. ARISA fingerprints from seawater at 1500 meters depth (DW1500), 2500 meters depth (DW 2500), 3300 meters depth (DW3300), Discovery interface (DI) and Discovery brine water (DB).


    Objective 3. Life in Discovery?

    Table 2. Enzymatic activities, CH4 production and sulfate reduction rates in Discovery interface and brine waters.


    Objective 3. Life in Discovery?

    • 16S rDNA data (clone libraries and ARISA) show that Discovery brine, interface and seawater above Discovery has its own specific microbial community.

    • Halorhabdus utahensis, characterized by high MgCl2 toleration, becomes enriched in Discovery.

    • The enzyme activity studies show that microbial enzymes from the Discovery brine are active under Discovery brine water conditions.

    • Natural methane production and sulfate reduction is observed in Discovery brine and interface samples.

    • To be included: t-RFLP???


    Conclusions

    • Geochemical conditions in the brines determines the establishment of a certain microbial community. Thus, microbial communities become adapted to the specific geochemical conditions in the brines.

    • Conditions in brines supports growth of microbes important in the sulfur cycle, heterotrophic microorganisms and (possible) methanogens. These methanogens might belong to a new subdivision in the archaea tree.

    • Microbial life exists in the Discovery brine. The first report that microbial life is possible at ~ 5 M MgCl2


    Discussion

    • Is it good enough for Nature??

    • What geochemical data should be included in the cluster analysis?

    • Can the meiofauna data be included to support the conclusions drawn in this manuscript and is the meiofauna data clear and strong enough to draw conclusions??


    Time plan

    • We (Paul/Henk/Biodeep) need publications!!!!!!!!!!!

    • Therefore timeplan:

      • Within two weeks after this meeting I need all data

      • Subsequently one month to finish first version of ms

      • Two weeks time to comment on first version

      • Two weeks time to rewrite ms

      • Etc.

    • I’m planning on using this time plan very strict!!!!!!


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