Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Sulfate reducing prokaryotes in the Eastern Mediterranean A functional genomics approach • Sulfate reduction: – SO42- + 8H+ +8e– Electron donors S2- + 4H2O • Organic matter (lactate, acetate, ethanol, etc) • H2 • CH4 – Important in anoxic marine ecosystems but occurs in other ecosystems as well. Sulfate reducing prokaryotes • Dissimilatory sulfite reductase (DSR) – Enzyme involved in sulfate reduction – Catalysis following reaction: – The gene encoding for enzyme contains conservative and variable sites – Therefore a good gene to study diversity of sulfate reducing prokaryotes in the environment Deep hypersaline brines • Eastern Mediterranean contains hypersaline brines which are located at the deep-sea. • These brines are characterized by high salinity (up to 30% salt), high pressure (up to 350 bar) absence of oxygen and relatively high concentrations of sulfate and sulfide. Deep hypersaline brines • 16S rDNA sequence analysis revealed many sequences related to δproteobacteria. • Sulfate reduction rates ranged from 8 to 80 µmol H2S day-1 in the different brines. • Conclusion: – Sulfate reduction occurs as a metabolic process in deep hypersaline brines Objectives • What is the similarity of SRP communities between different sampling sites • Is their similarity between DSR sequence analysis and 16S rDNA sequence analysis. • What is the community structure of sulfate reducing prokaryotes (SRP)? Mat & Meth • Study sites: – L’Atalante brine and interface – Urania brine and interface – Eastern Mediterranean deep-sea sediment three layers • α- and β-subunit of DSR gene amplified • 700 bp of α-subunit were sequenced • Amino acid alignments were created and trees were constructed using these alignments Diversity and Similarity Diversity Atalante brine Atalante interface Urania brine Urania interface Sed1 Sed2 Sed3 DSR δ-16S DSR δ-16S DSR δ-16S DSR δ-16S DSR DSR DSR Sequences 100 18 100 6 100 28 100 16 22 21 10 Shannon index 1.5 2.0 0.99 1.3 0.28 0.71 1.67 1.2 1.3 2.0 1.6 Urania interface Sed1 Sed2 Sed3 Similarity AB DSR/16S AI DSR/16S UB DSR/16S UI DSR/16S Sed1 DSR/16S Sed2 DSR/16S Sed3 DSR/16S Atalante brine Atalante interface Urania brine DSR δ-16S DSR δ-16S DSR δ-16S DSR δ-16S DSR DSR DSR 1 1 0.26 0.00 0.00 0.22 0.00 0.05 0.00 0.00 0.00 1 1 0.00 0.00 0.00 0.03 0.00 0.00 0.00 1 1 0.00 0.31 0.00 0.00 0.00 1 1 0.00 0.00 0.00 1 0.00 0.00 1 0.00 1 Nearest relatives DSR-protein OTU Nearest relative similarity 46 AB 56 Desulfohalobium retbaense 83.4% 11 AB 29 Desulfohalobium retbaense 83% 11 AB 90 Desulfobacter vibrioformis 85% 23 AB 95 uncultured deep-sea hydrothermal vent 1 77% 75 AI 36 Desulfobacter vibrioformis 86% 6 AI 18 Desulfobacter vibrioformis 86% 5 AI 60 unidentified bacterium 87% 8 AI 37 uncultured deep-sea hydrothermal vent 1 76% 94 UB 28 uncultured deep-sea hydrothermal vent 1 76% 11 UI 91 Desulfobacter vibrioformis 85% 5 UI 15 Desulfobacterium oleovorans 82% 5 UI 7 Desulfobacterium oleovorans 85% 6 UI 43 uncultured bacterium 1 84% 11 UI 14 unidentified bacterium 92% 52 UI 75 unidentified bacterium 93% 13 Sed1 01 uncultured bacterium 2 84% 7 Sed2 09 uncultured Guaymas Basin 64% 3 Sed3 01 uncultured deep-sea hydrothermal vent 1 84% Phylogenetic tree DSRa-protein Phylogenetic tree δ-16S rDNA δ-Proteobacterial family distribution 100 90 Percentage of clones 80 70 60 Dulfohalobiaceae Desulfobacteriaceae 50 Desulfovibrionaceae Desulfobulbaceae 40 30 20 10 0 DSR AB 16S DSR 16S AI DSR 16S UI DSR 16S UB Origin of sulfate reduction Desulfobotulus sapovorans Desulfohalobium retbaense Desulfobacula toluolica Desulfovibrio fructosovorans Desulfosarcina variabilis Desulfotomaculum kuznetsovii Archaeoglobus profundus Archaeoglobus fulgidus Desulfotomaculum ruminis Thermodesulfovibrio islandicus Percentage of clones without insertion 100 90 percentage of clones 80 70 60 50 40 30 20 10 0 AB AI UB UI sed1 sed2 sed3 Conclusions/Discussion • All sites sampled showed diverse sulfate reducing prokaryotic communities except Urania brine. • The low diversity in Urania brine has been observed with total community structure as well. • Similarity of DSRa sequences between sites is very low thus each site studied had a unique sulfate reducing community. • There are some differences between site similarity of DSRa and δ-16S rDNA. Can be related to OTU cut-off value or that not all DSRa sequences are from δ-proteobacteria Conclusions/Discussion • The obtained DSR-sequences show low similarity with GenBank sequences and represent yet-unknown DSRa genes from sulfate reducing prokaryotes. • The DSRa and 16S rDNA tree topology and family distribution were similar for AI, UB and AB. • This was not true for UI. UI DSRa sequences distantly related to Desulfotomaculum but no 16S rDNA sequences related to that cluster. Conclusions/Discussion • This can be caused by – 1. These DSRa sequences are related to the δ-16S rDNA sequences but this cannot be seen because tree topologies are non congruent – 2. 16S rDNA sequences of UI related to unknown or candidate division clusters, from which metabolic capacities are unknown, are from prokaryotes with sulfate reducing capabilities. Conclusions/Discussion • Allmost all DSRa sequences from deep-sea brines and interfaces contain an insertion in αsubunit. – This might indicate that sequences are from nonthermophilic sulfate reducing prokaryotes • Most DSRa sequences from intermediate layer sediment miss this insertion. – This might indicate that sequences are thermophilic sulfate reducing prokaryotes. This agrees with the thermogenic history. Why these sequences only occur at the intermediate layer is presently unknown.