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Melitza Crespo-Medina September 12, 2007

Aerobic Chemosynthesis and Microbial Hg-Resistance at Diffuse Flow Hydrothermal Vents from the East Pacific Rise at 9ºN. Melitza Crespo-Medina September 12, 2007. Goals.

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Melitza Crespo-Medina September 12, 2007

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  1. Aerobic Chemosynthesis and Microbial Hg-Resistance at Diffuse Flow Hydrothermal Vents from the East Pacific Rise at 9ºN Melitza Crespo-Medina September 12, 2007

  2. Goals • To study the abundance and diversity of aerobic chemosynthetic thiosulfate oxidizing bacteria from diffuse flow hydrothermal vents • To measure the concentration of mercury (Hg) in vent fluids • To investigate microbially mediated detoxification of heavy metals (such as mercury) by hydrothermal vent bacteria

  3. Diffuse flow fluid sampling: ‘04, ‘05 and ‘07 Direct enrichment MPN and bacterial isolation Pure cultures Total Hg (THg) concentration: 2.8 to 88.7 ng/L Sequencing and Identification MPN with Hg and bacterial isolation Identification of merA gene Methods

  4. merR merT merP merA merB merD Loss of Hg(II) during growth of strain EPR3 () Hg(II) remaining in solution, (D) OD600 (optical density at 600 nm () Remaining Hg(II) in uninoculated medium Vetriani et al., 2005. Appl. Environ. Microbiol. 71: 220-226 Hg detoxification The mer operon: Mercuric reductase enzyme Hg2+ Hg0

  5. Total cell counts: 107 to 108cells/ml • MPN counts (no Hg): 103 to 107 cells/ml • MPN counts with Hg: 102 to 104cells/ml Abundance of chemosynthetic thiosulfate oxidizing bacteria Pre-eruption Post-eruption

  6. Gram + Alphaproteobacteria Gammaproteobacteria Phylogenetic analysis of selected thiosulfate oxidizing bacteria isolated form deep-sea vents

  7. CM OM PS • Gamma proteobacterium • 95 % similarity to Salinisphaera shabanense • Isolated in 142-A at 28 ºC • Facultative autotroph • Grows in 142+A, ASW, Low strength ASW (0.5 g/l peptone and 0.1 g/L YE) • Acid producing • Growth temperature range: 20 - 45 ºC Optimal growth temp.: 28 - 37 ºC Phylogenetic analysis of selected thiosulfate oxidizing bacteria isolated form deep-sea vents

  8. Conclusion • The abundance of aerobic chemosynthetic thiosulfate oxidizers ranges from 103to 107 cells/ml of hydrothermal fluid • Diffuse flow fluids are enriched with Hg, with concentrations that can be considered toxic to living organisms • 0.2 to 24.6 % of the chemosynthetic thiosulfate oxidizing organisms are also Hg resistant • In some cases the abundance of Hg resistant organisms correlates to the THg concentration (e.g., at Tica). • THg concentration was also measured from focused flow vent fluids and concentrations ranged from 701.3 to 2213.1 ng/L • Future work include mercury volatilization assays and environmental surveys of merA genes

  9. Acknowledgement • Dr. Costantino Vetriani (advisor) and Dr. Tamar Barkay (co-advisor ) • Vetriani and Barkay’s lab members • Dr. John Reinfelder and Derek Wright (Rutgers University) • Nicolas Bloom (Frontier Geoscience) • Dr. George Luther III (University of Delaware) • Dr. Richard Lutz (Rutgers University) • Dr. Timothy Shank (WHOI) • Crew of R/V Atlantis and crew and pilots of the DSV Alvin • Funding: • NIH grant GM58389 • NSF Graduate Research Fellowship Program • NSF grant 03-27353 and 04-56676

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