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

 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

Atkins et al. 2002

 Vestimentiferans, clams & mussels  Harbor symbiotic chemoautotrophic bacteria  Spatially separate acquisition of oxygen and sulfide  Free-living chemoautotrophic bacteria  Thermophiles  Mesophiles  Psychrophiles

 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  merA gene  Mercuric reductase  Organomercury Hg(II)  inert, monoatomic Hg(0)

 Collected vent, plume and control samples from EPR 9° N  Isolated and sequenced using 16S for identification Alcanivorax Psychrobacter Pseudoalteromonas

 T opt & Hg resistance  Various concentrations of HgCl2 in ASW (0 – 75 μM)  Plume and vent (mesophilic and thermophilic) displayed higher T opt & higher Hg resistance than controls  Hg volatilization  Add HgCl2 to cultures and add to volatilization buffer in microplate

 Only four strains were successfully sequenced  1 mesophilic, 3 thermophilic  Phylogenetic analysis revealed a new cluster of merA from thermophilic strains.

 Mesophilic and thermophilic strains from the hydrothermal vent region were resistant to mercury, while control psychrophilic strains were sensitive.  New cluster of merA in thermophilic bacteria  Elevated T opt of MR suggests that this enzyme is of thermophilic origin

 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?

 Atkins, M.S., Hanna, M.A., Kupetsky, E.A., Saito, M.A., Taylor, C.D. & Wirsen, C.O Tolerance of flagellated protists to high sulfide and metal concentrations potentially encountered at deep-sea hydrothermal vents. Marine Ecology Progress Series. 226:  Barkay, T., Miller, S.M. & Summers, A.O Bacterial mercury resistance from atoms to ecosystems. FEMS Microbiology Reviews. 27:  German, C.R., Baker, E.T. & Klinkhammer, G Regional setting of hydrothermal activity, pp 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 Microbial interactions with hydrothermal fluids, pp 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 Prokaryotic lifestyles in deep-sea habitats. Extremophiles. 12:  Nakamura, K. & Nakahara, H Simplified X-Ray Film Method for Detection of Bacterial Volatilization of Mercury Chloride by Escherichia coli. Applied and Environmental Microbiology. 54(11):  Vetriani, C., Chew, Y.S., Miller, S.M., Yagi, J., Coombs, J., Lutz, R.A. & Barkay, T Mercury adaptation among bacteria from a deep-sea hydrothermal vent. Applied and Environmental Microbiology. 71(1):