User:Carolinewebster2021

From MicrobeWiki, the student-edited microbiology resource

Overview

Photo of white smoker located at the Champagne vent, Northwest Eifuku volcano, Marianas Trench Marine National Monument


By Caroline Webster

Detailed Environmental Description

White smokers are deep-sea hydrothermal vents located off-axis from mid-ocean ridges. They are high-pH (around 9-9.8) and are typically 260-300˚C, though can be as cool as 45-75˚C.[1][2] Hydrothermal vents form from superheated seawater that circulates in the ocean's crust, dissolving toxic minerals and gases. As pressure builds, the water is released through mineralized chimneys into contrastingly freezing ocean water, creating hot plumes. White smokers should not be confused with their more common relatives, black smokers, which are typically located directly along mid-ocean ridges and whose plumes are much hotter (around 360˚C). Black smokers are usually larger and gets their black color from iron monosulfide; white smokers emit lighter-hued chemicals such as barium, calcium and silicon. Furthermore, white smokers are "characterized by an axial zone of high porosity that favors outward percolation of hot fluids from all surfaces", whereas black smokers release hot water from only the top chimney opening. [3][4]


Overview of Microbial Ecology as it is known

Hydrothermal vents create unique conditions for microbial communities. These communities are dominated by hyperthermophilic anaerobic archaea and bacteria [5]. Bacteria living in these plumes rely on cemosynthesis, conversitng minerals into organic material in the absense of sunlight. Due to the stark constrast between vent plumes and surrounding seawater, plumes are characterized by steep gradients. According to a study conducted Kormas et. al of a white smoker from the East Pacific Rise (9°N), the inner chimney walls, which can reach temperatures over 250˚C, are home to thermophilic and hyperthermophilic prokaryotes such as methanogens, anaerobic hydrogen oxidizers, NO3/Fe/S°/SO4 reducers and fermentative heterotrophs [3][6]. Outer chimney walls come in contact with cool, oxygenated sea water and host a denser mesophilic community, "consisting mostly of H2S‐, Fe‐ and Mn‐oxidizers, oxygen‐respiring hydrogen oxidizers, and aerobic methanotrophs"[3] [7]. 16S rRNA gene clone libraries from the Kormas study were dominated by epsilon-Proteobacteria, Bacteroidetes, Thermales and Aquificales bacterial phlya along with hyperthermophilic Thermococcales, Archaeoglobales, Desulfurococcales and Thermoproteales archaeal orders. The superheated pyrrhotite-rich chimney center was populated only with epsilon-Proteobacteria "related to meophilic isolates". [3]

Key Microbial Players

Phylogenetic tree of bacterial phyla Proteobacteria, Bacteroidetes, Thermales and Aquificales found in white smoker [3]
Phylogenetic tree of archaeal phyla present in white smoker (Kormas)

Information on key microbial players is derived from Kormas et. al 16S rRNA gene cloning and sequencing. The first key microbial player to mention is the Epsilon-Proteobacteria. Strains of Epsilon-Proteobacteria are mainly found in the chimney top, porous central orifice walls at the chimney top, and in the outer part of the middle chimney layer.[3] Clones are related to Rimicaris exoculata (polz) and Alvinella pompejana (Cary) and were derived from symbionts of Alvinellid polychaetes [3] [8]. Cultured strains are described as mesophilic or moderate thermophlic chemoautotrophs [3] and "all strains use nitrate or oxygen as electron acceptors, and hydrogen, thiosulfate and elemental sulfur as electron donors". [5] [9]
Next, Kormas et. al identified Thermales and Aquificales are important hyperthermophilic bacteria players. They are found "located at the top chimney surface, the porous central orifice walls at the top of the chimney and the outer part of the middle layer" (Kormas). Strains are closely realted to Oceanithermus profundus, a thermophilic microaerophilic and facultatively chemolithotrophic bacterium (Kormas, Miroshnickenko). The closest cultured relative to Aquificales is Persephonella, "thermophilic, nitrate‐ and oxygen‐respiring, sulfur‐, thiosulfate‐ and hydrogen‐oxidizing chemolithoautotrophic bacteria" with optimal growth at 70-73˚C (Kormas, Götz).[3]Cite error: Invalid <ref> tag; invalid names, e.g. too many While it is still unclear how organic compounds evolved, hydrothermal vents are a plausible geological context for where it could have happened. These vents provide the necessary geothermal gradients to facilitate such reactions [10] .

Conclusion

References

  1. Arndt N. (2011) White Smoker. In: Gargaud M. et al. (eds) Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg
  2. Kelley, D.S., Karson, J.A., Blackman, D.K., Fruh-Green, G.L., Butterfield, D.A., Lilley, M.D., Olson, E.J., Schrenk, M.O., Roe, K.K., Lebon, G.T., Rivizzigno, P., and the, A.T.S.P., 2001, An off-axis hydrothermal vent field near the Mid-Atlantic Ridge at 30[deg N: Nature, 412, 145-149.]
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 [1]
  4. Koski, R.A., Jonasson, I.R., Kadko, D.C., Smith, V.K., Wong, F.L. (1994) Compositions, growth mechanisms, and temporal relations of hydrothermal sulfide‐sulfate‐silica chimneys at the northern Cleft segment, Juan de Fuca Ridge. J Geophys Res 99: 4813–4832.
  5. 5.0 5.1 Takai, K., Nealson, K.H., Horikoshi, K. (2004) Hydrogenimonas thermophila gen. nov., sp. nov. a novel thermophilic, hydrogen‐oxidizing chemolithoautotroph within the epsilon‐Proteobacteria, isolated from a black smoker in a Central Indian Ridge hydrothermal field. Int J Syst Evol Microbiol 54: 25–32.
  6. McCollom, T.M., Shock, E.L. (1997) Geochemical constraints on chemolithoautotrophic metabolism by microorganisms in seafloor hydrothermal systems. Geochim Cosmochim Acta 61: 4375–4391.
  7. Reysenbach, A.‐L., Götz, D., Yernool, D. (2001) Microbial diversity of marine and terrestrial thermal springs. In Biodiversity of Microbial Life: Foundation of Earth's Biosphere. Staley, J.T., Reysenbach, A.‐L. (eds). New York, NY, USA: Wiley‐Liss, pp. 345–421.
  8. Cary, S.C., Cottrell, M.T., Stein, J.L., Camacho, F., Desbruyeres, D. (1997) Molecular identification and localization of filamentous symbiotic bacteria associated with the hydrothermal vent annelid Alvinella pompejana . Appl Environ Microbiol 63: 1124–1130.
  9. Inagaki, F., Takai, K., Kobayashi, H., Nealson, K.H., Horikoshi, K. (2003) Sulfurimonas autotrophica gen. nov., sp. nov., a novel sulfur‐oxidizing epsilon‐Proteobacterium isolated from hydrothermal sediments in the Mid‐Okinawa Trough. Int J Syst Evol Microbiol 53: 1801–1805.
  10. Cite error: Invalid <ref> tag; no text was provided for refs named Morowitz



Authored for Earth 373 Microbial Ecology, taught by Magdalena Osburn, 2020, NU Earth Page.