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Mercury adaptation among bacteria from a deep-sea hydrothermal vent Vetriani et al. 2005

Mercury adaptation among bacteria from a deep-sea hydrothermal vent Vetriani et al. 2005. East Pacific Rise. http://www.mbari.org/molecular/images/EPR%20mussel-map.jpg. East Pacific Rise Physical properties. First discovered in 1979 Tectonic plates spreading apart and new crust being formed

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Mercury adaptation among bacteria from a deep-sea hydrothermal vent Vetriani et al. 2005

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  1. Mercury adaptation among bacteria from a deep-sea hydrothermal ventVetrianiet al. 2005

  2. East Pacific Rise http://www.mbari.org/molecular/images/EPR%20mussel-map.jpg

  3. East Pacific RisePhysical properties • First discovered in 1979 • Tectonic plates spreading apart and new crust being formed • Precipitate forms chimney-like constructs • Fluids around 350-360°C (662 – 680°F) • The rise of a plume is a function of water column stratification and the strength of the source

  4. East Pacific RiseChemical properties • Mercury-rich due to cinnabar (HgS) deposits • Vent fluids rich in metal sulfides mix with oxygen-rich, cold water • Low toxicity, low bioavailability  more toxic, more bioavailable • Creates large chemical gradient between vent source and plume http://www.mineralatlas.com/mineral%20photos/C/

  5. Ambient seawater vs. vent fluids Atkins et al. 2002

  6. East Pacific RiseBiological properties • Vestimentiferans, clams & mussels • Harbor symbiotic chemoautotrophic bacteria • Spatially separate acquisition of oxygen and sulfide • Free-living chemoautotrophic bacteria • Thermophiles • Mesophiles • Psychrophiles http://bioweb.uwlax.edu/bio203/s2007/rossing_jaco/images/blacksmoker.jpg http://www.compostinfo.com/images/Tutorial/microbes

  7. Mercuryresistance • First reported in 1960 in Staphylococcus aureus • Unique: only bacterial metal resistance mechanism that transforms its toxic target on a large scale • Efflux pumps or extracellular sequestration most common • merAgene • Mercuric reductase • OrganomercuryHg(II)  inert, monoatomic Hg(0) http://www.sacriver.org/images/mercury/figure4.jpg

  8. The study… • Collected vent, plume and control samples from EPR 9° N • Isolated and sequenced using 16S for identification Pseudoalteromonas Alcanivorax Psychrobacter http://microbewiki.kenyon.edu/images/6/64/Coccoid http://genome.jgi-psf.org/pseat/pseat.jpg http://jb.asm.org/content/vol188/issue24/cover.dtl

  9. The study (cont’d)… • Topt & Hg resistance • Various concentrations of HgCl2 in ASW (0 – 75 μM) • Plume and vent (mesophilic and thermophilic) displayed higher Topt& higher Hg resistance than controls • Hg volatilization • Add HgCl2 to cultures and add to volatilization buffer in microplate

  10. The study (cont’d)…

  11. The study (cont’d)… • Only four strains were successfully sequenced • 1 mesophilic, 3 thermophilic • Phylogenetic analysis revealed a new cluster of merAfrom thermophilic strains.

  12. Conclusions • Mesophilic and thermophilic strains from the hydrothermal vent region were resistant to mercury, while control psychrophilic strains were sensitive. • New cluster of merAin thermophilic bacteria • Elevated Topt of MR suggests that this enzyme is of thermophilic origin

  13. What do you think? • Should they have tested volatilization in more strains? • Only used EPR3, 6, 7 and 8 • Did they support their hypothesis that thermophilic bacteria are the source of the MR in mesophilic bacteria? • Deep-sea vents origin of life? • Evolution of metal resistance in deep-sea vents? • Note to self: How fast does photodegradation occur in shallow waters?

  14. References • Atkins, M.S., Hanna, M.A., Kupetsky, E.A., Saito, M.A., Taylor, C.D. & Wirsen, C.O. 2002. Tolerance of flagellated protists to high sulfide and metal concentrations potentially encountered at deep-sea hydrothermal vents. Marine Ecology Progress Series. 226:63-75. • Barkay, T., Miller, S.M. & Summers, A.O. 2003. Bacterial mercury resistance from atoms to ecosystems. FEMS Microbiology Reviews. 27:355-384. • German , C.R., Baker, E.T. & Klinkhammer, G. 1995. Regional setting of hydrothermal activity, pp. 3-15. In Parson, L.M., Walker, C.L. & Dixon, D.R. (eds.), Hydrothermal vents and processes. The Geological Society. Geological Society Publishing House, Bath, UK. • Jannasch, H.W. 1995. Microbial interactions with hydrothermal fluids, pp. 273-296. In Humphris, S.E., Zierenberg, R.A., Mullineaux, L.S. & Thomson, R.E. (eds.), Seafloor Hydrothermal Systems; Physical, Chemical, Biological, and Geological Interactions. American Geophysical Union, Washington, DC USA. • Lauro, F.M. & Bartlett, D.H. 2008. Prokaryotic lifestyles in deep-sea habitats. Extremophiles. 12:15-25. • Nakamura, K. & Nakahara, H. 1988. Simplified X-Ray Film Method for Detection of Bacterial Volatilization of Mercury Chloride by Escherichia coli. Applied and Environmental Microbiology. 54(11):2871-2873. • Vetriani, C., Chew, Y.S., Miller, S.M., Yagi, J., Coombs, J., Lutz, R.A. & Barkay, T. 2005. Mercury adaptation among bacteria from a deep-sea hydrothermal vent. Applied and Environmental Microbiology. 71(1):220-226.

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