Transcript Extremophiles - People Server at UNCW

http://www.mbari.org/molecular/images/EPR%20mussel-map.jpg
First discovered in 1979
Tectonic plates spreading
apart and new crust being
formed
 Precipitate forms chimneylike 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
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Mercury-rich due to cinnabar (HgS)
deposits
 Vent fluids rich in metal sulfides mix with
oxygen-rich, cold water
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 Low toxicity, low bioavailability 
more toxic, more bioavailable
 Creates large chemical gradient
between vent source and plume
http://www.mineralatlas.com/mineral%20photos/C/
Atkins et al. 2002
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Vestimentiferans, clams & mussels
 Harbor symbiotic chemoautotrophic
bacteria
 Spatially separate acquisition of
oxygen and sulfide
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Free-living chemoautotrophic
bacteria
http://bioweb.uwlax.edu/bio203/s2007/rossing_jaco/images/blacksmoker.jpg
 Thermophiles
 Mesophiles
 Psychrophiles
http://www.compostinfo.com/images/Tutorial/microbes
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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
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merA gene
 Mercuric reductase
 Organomercury Hg(II)  inert,
monoatomic Hg(0)
http://www.sacriver.org/images/mercury/figure4.jpg
Collected vent, plume and control samples from
EPR 9° N
 Isolated and sequenced using 16S for identification
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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
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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
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Hg volatilization
 Add HgCl2 to cultures and add to volatilization buffer in
microplate
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Only four strains were
successfully sequenced
 1 mesophilic, 3 thermophilic
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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 Topt of MR suggests that this enzyme is of
thermophilic origin
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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?
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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.