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University of Essex

University of Essex. BIODEEP-WP5. Understanding of ecological relations between the microbial communities and the functioning of DHAB environments. Andrea Sass , Terry McGenity, Boyd McKew. Proteobacteria:. mostly from interfaces some sulfur-oxidizing bacteria

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University of Essex

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  1. University of Essex BIODEEP-WP5 Understanding of ecological relations between the microbial communities and the functioning of DHAB environments Andrea Sass , Terry McGenity, Boyd McKew

  2. Proteobacteria: mostly from interfaces some sulfur-oxidizing bacteria many related to bacteria found in deep-sea environments all grow on sea water medium, some extremely halotolerant • isolates are marine bacteria derived from the oxic water column • some isolates could benefit from the conditions in the interface (particularly sulfur-oxidizing bacteria) Future: investigation of an extremely halotolerant, aerobic, aerotactic strainn from Urania basin interface

  3. Bacillus related isolates: almost all derived from sediments  no correlation between phylogeny and basin of origin  vast majority of tested strains only halotolerant  (some very halotolerant and also facultatively anaerobic)  probably derived from dormant spores  six strains obligately halophilic (no growth below 3.5% salt, optimum at 5-10% salt)  two strains isolated anaerobically in highly saline medium

  4. Strain AS4 3% 5% 10% 15% 20% 20% 25 % 30%

  5. Strain US13 5% 10% 15% 20% 22% 25% 27% 30% 5% 10% 15% 20% 22% 25% 27% 30%

  6. other characteristics: • anaerobic growth, also at high salt concentrations • favours moderate temperatures and pH • substrates used: amino acids, betaine, organic acids, yeast extract possibly active in situ Future: characterization of Halobacillus-related strains growing anaerobically at 20% salt

  7. Physiological properties of anerobic isolates •  Halanaerobiaceae : • all except one (from DS) extremely halophilic • distinct species from each basin, some isolated repeatedly • strains derived from BI similar to isolate from another DHAB (Red Sea) •  CFB: moderately halophilic •  Clostridia: moderately halophilic •  Methanogens: extremely halophilic • e-Proteobacterium: moderately halophilic, reduces sulfur compounds and nitrate •  Halorhabdus sp.: facultative anaerobe, extremely halophilic

  8. Active in situ? • Methanogens, Haloanaerobiaceae and Halobacterium possibly active in situ in the brines • e-Proteobacterium and CFB could thrive in the interface • Clostridia probably derived from dormant spores

  9. Sequences similar to three cultivates strains were also found in clone libraries made from the basins Archaea: AN-AI3 (Halorhabdus utahensis 99%): !99% identity to clone DLIA-31 AN-AS7 (Methanohalophilus mahii 99%): ! 99% identity to clones ULIA-84, DLIA-189, ALIA-123, ABBA-51 Eubacteria: AN-BI4 (CFB): !98% identity to clone BBBB-69 (tRFLP-fragments with lengths analogous to fragments derived from AN-BI4 occur in samples from interfaces and brines)

  10. l‘Atalante sediment: • extremely halophilic fermenting organisms isolated from top layers • Bannock sediment: • only organisms probably not active in situ isolated • t-RFLP profile like that from brine • no anaerobic isolates from brines l‘Atalante basin upper sediments contain bacterial population different from brine

  11. some organisms possibly active in the brines/interfaces could be cultivated vast majority of organisms inhabiting the DHAB remain uncultivated cultivation-independent approaches needed for understanding the function of DHAB environments

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