Much interest has been generated by the discoveries of biodiversity associated with seamounts. The volcanically active portion of these undersea mountains hosts a remarkably diverse range of unusual microbial habitats, from black smokers rich in sulfur to cooler, diffuse, iron-rich hydrothermal vents. As such, seamounts potentially represent hotspots of microbial diversity, yet our understanding of the microbiology of seamounts is still in its infancy. Here, we discuss recent work on the detection of seamount microbial communities and the observation that specific community groups may be indicative of specific geochemical scenarios, such as iron and sulfur cycling. These observations are based on the metabolisms predicted by phylogenetic characteristics exhibited by the dominant populations found within these microbial communities as compared to the closest related isolate found in culture. Therefore, these studies combine the use of both cultivation-dependent and -independent analyses. Cultivation-independent studies were primarily completed using cloning and sequencing techniques targeting small subunit ribosomal gene (SSU rDNA) biomarkers along with similar biomolecular tools like terminal-restriction fragment length polymorphism (T-RFLP) and quantitative polymerase chain reaction (Q-PCR), which allow for the determination of phylotypes (analogous to species). We discuss the notion of Zetaproteobacteria and/or Epsilonproteobacteria being the most common members of hydrothermal habitats associated with seamounts exhibiting volcanic activity. Another noneruptive seamount scenario is also examined, for example, South Chamorro Seamount, an active forearc serpentinite mud volcano.

Emerson, D., and C.L. Moyer. 2010. Microbiology of seamounts: Common patterns observed in community structure. Oceanography 23(1):148–163, https://doi.org/10.5670/oceanog.2010.67.

Campbell, B.J., A.S. Engel, M.L. Porter, and K. Takai. 2006. The versatile ε-proteobacteria: Key players in sulphidic habitats. Nature Reviews Microbiology 4:458–468.
1. Chadwick, W.W., D.A. Butterfield, R.W. Embley, V. Tunnicliffe, J.A. Huber, S.L. Nooner, and D.A. Clague. 2010. Spotlight 1: Axial Seamount. Oceanography 23(1):38–39 
2. Chivian, D., E.L. Brodie, E.J. Alm, D.E. Culley, P.S. Dehal, T.Z. DeSantis, T.M. Gihring, A. Lapidus, L.-H. Lin, S.R. Lowry, and others. 2008. Environmental genomics reveals a single-species ecosystem deep within Earth. Science 322:275–278.
3. Connell, L., A. Barrett, A. Templeton, and H. Staudigel. 2009. Fungal diversity associated with an active deep sea volcano: Vailulu’u Seamount, Samoa. Journal of Geomicrobiology 26:597–605.
4. Cowen, J.P., S.J. Giovannoni, F. Kenig, H.P. Johnson, D. Butterfield, M.S. Rappe, M. Hutnak, and P. Lam. 2003. Fluids from aging ocean crust that support microbial life. Science 299:120–123.
5. Curtis, A.C., C.G. Wheat, P. Fryer, and C.L. Moyer. 2009. Mariana forearc serpentine mud volcanoes harbor novel communities of extremophilic Archaea. Poster Abstracts: IODP New Ventures in Exploring Scientific Targets (INVEST), September 23–25, 2009, Bremen, Germany. 
6. Davis, R.E., and C.L. Moyer. 2008. Extreme spatial and temporal variability of hydrothermal microbial mat communities along the Mariana Island Arc and southern Mariana back-arc system. Journal of Geophysical Research 113, B08S15, http://10.1029/2007JB005413.
7. deRonde, C.E.J., E.T. Baker, G.J. Massoth, J.E. Lupton, I.C. Wright, R.A. Feely, and R.R. Greene. 2001. Intra-oceanic subduction-related hydrothermal venting, Kermadec volcanic arc, New Zealand. Earth and Planetary Science Letters 193:359–369.
8. deRonde, C.E.J., E.T. Baker, G.J. Massoth, J.E. Lupton, I.C. Wright, R.J. Sparks, S.C. Bannister, M.E. Reyners, S.L. Walker, R.R. Greene, and others. 2007. Submarine hydrothermal activity along the mid-Kermadec Arc, New Zealand: Large-scale effects on venting. Geochemistry, Geophysics, Geosystems 8(7), Q07007, http://10.1029/2006GC001495.
9. Duennebier, F.K., N.C. Becker, J. Caplan-Auerbach, D.A. Clague, J. Cowen, M. Cremer, M. Garcia, F. Goff, A. Malahoff, G.M. McMurtry, and others. 1997. Researchers rapidly respond to submarine activity at Loihi Volcano, Hawaii. Eos, Transactions, American Geophysical Union 78:229–233.
10. Edwards, K.J., W. Bach, and T.M. McCollom. 2005. Geomicrobiology in oceanography: Microbe-mineral interactions at and below the seafloor. TRENDS in Microbiology 13:449­–456.
11. Elsaied, H., H.W. Stokes, T. Nakamura, K. Kitamura, H. Fuse, and A. Maruyama. 2007. Novel and diverse integron integrase genes and integron-like gene cassettes are prevalent in deep-sea hydrothermal vents. Environmental Microbiology 9:2,298–2,312.
12. Embley, R.W., E.T. Baker, D.A. Butterfield, W.W. Chadwick, J.E. Lupton, J.A. Resing, C.E.J. de Ronde, K. Nakamura, V. Tunnicliffe, J. Dower, and S.G. Merle. 2007. Exploring the submarine ring of fire, Mariana Arc–Western Pacific. Oceanography 20(4):68–79.
13. Embley, R.W., W.W. Chadwick, D. Clague, and D. Stakes. 1999. 1998 Eruption of Axial Volcano: Multibeam anomalies and sea-floor observations. Geophysical Research Letters 26:3,425–3,428.
14. Emerson, D., and C.L. Moyer. 2002. Neutrophilic Fe-oxidizing bacteria are abundant at the Loihi Seamount hydrothermal vents and play a major role in Fe oxide deposition. Applied and Environmental Microbiology 68:3,085–3,093.
15. Emerson, D., J.A. Rentz, T.G. Lilburn, R.E. Davis, H. Aldrich, C. Chan, and C.L. Moyer. 2007. A novel lineage of Proteobacteria involved in formation of marine Fe-oxidizing microbial mat communities. PLoS ONE 2:e667, http://10.1371/journal.pone.0000667.
16. Fisher, A.T., and C.G. Wheat. 2010. Seamounts as conduits for massive fluid, heat, and solute fluxes on ridge flanks. Oceanography 23(1):74–87.
17. Forget, N.L., S.A. Murdock, and S.K. Juniper. In press. Bacterial diversity in Fe-rich hydrothermal sediments at two South Tonga Arc submarine volcanoes. Geobiology.
18. Fryer P., J. Gharib, K. Ross, I. Savov, and M.J. Mottl. 2006. Variability in serpentinite mudflow mechanisms and sources: ODP drilling results on Mariana forearc seamounts. Geochemistry, Geophysics, Geosystems 7(8), Q08014, http://10.1029/2005GC001201.
19. Fryer, P., C.G. Wheat, and M.J. Mottl. 1999. Mariana blueschist mud volcanism: Implications for conditions within the subduction zone. Geology 27:103–106.
20. Glazer, B.T., and O.J. Rouxel. 2009. Redox speciation and distribution within diverse iron-dominated microbial habitats at Loihi Seamount. Journal of Geomicrobiology 26:606–622.
21. Gold, T. 1992. The deep, hot biosphere. Proceedings of the National Academy of Sciences of the United States of America 89:6,045–6,049.
22. Higashi, Y., M. Sunamura, K. Kitamura, K. Nakamura, Y. Kurusu, J. Ishibashi, T. Urabe, and A. Maruyama. 2004. Microbial diversity in hydrothermal surface to subsurface environments of Suiyo Seamount, Izu-Bonin Arc, using a catheter-type in situ growth chamber. FEMS Microbiology Ecology 47:327–336.
23. Hodges, T.W., and J.B. Olsen. 2009. Molecular comparison of bacterial communities within iron-containing flocculent mats associated with submarine volcanoes along the Kermadec Arc. Applied and Environmental Microbiology 75:1,650–1,657.
24. Huber, J.A., D.A. Butterfield, and J.A. Baross. 2002. Temporal changes in archaeal diversity and chemistry in a mid-ocean ridge subseafloor habitat. Applied and Environmental Microbiology 68:1,585­–1,594.
25. Huber, J.A., D.A. Butterfield, and J.A. Baross. 2003. Bacterial diversity in a subseafloor habitat following a deep-sea volcanic eruption. FEMS Microbiology Ecology 43:393–409.
26. Huber, J.A., H.P. Johnson, D.A. Butterfield, and J.A. Baross. 2006. Microbial life in ridge flank crustal fluids. Environmental Microbiology 8:88–99.
27. Ishibashi, J., K. Marumo, A. Maruyama, and T. Urabe. 2007. Direct access to the sub-vent biosphere by shallow drilling. Oceanography 20(1):24–25.
28. Jørgensen, B.B., and A. Boetius. 2007. Feast and famine: Microbial life in the deep-sea bed. Nature Reviews Microbiology 5:770–781.
29. Juniper, S.K., and Y. Fouquet. 1988. Filamentous iron-silica deposits from modern and ancient hydrothermal sites. Canadian Mineralogist 26:859–869.
30. Karl, D.M. 1995. Ecology of free-living, hydrothermal vent microbial communities. Pp. 35–124 in Microbiology of Deep-Sea Hydrothermal Vents. D.M. Karl, ed., CRC Press, Boca Raton, FL.
31. Karl, D.M., G.M. McMurtry, A. Malahoff, and M.O. Garcia. 1988. Loihi Seamount, Hawaii: A mid-plate volcano with a distinctive hydrothermal system. Nature 335:532–535.
32. Kato, S., K. Hara, H. Kasai, T. Teramura, M. Sunamura, J. Ishibashi, T. Kakegawa, T. Yamanaka, H. Kimura, K. Marumo, T. Urabe, and A. Yamagishi. 2009. Spatial distribution, diversity and composition of bacterial communities in sub-seafloor fluids at a deep-sea hydrothermal field of the Suiyo Seamount. Deep-Sea Research Part I 56:1,844–1,855.
33. Kennedy, C.B., S.D. Scott, and F.G. Ferris. 2003. Ultrastructure and potential sub-seafloor evidence of bacteriogenic iron oxides from Axial Volcano, Juan de Fuca Ridge, northeast Pacific Ocean. FEMS Microbiology Ecology 43:247–254.
34. Koppers, A.A.P., H. Staudigel, S.R. Hart, C. Young, and J.G. Konter. 2010. Spotlight 8: Vailulu’u Seamount. Oceanography 23(1):164–165.
35. Langley, S., P. Igric, Y. Takahashi, Y. Sakai, D. Fortin, M.D. Hannington, and U. Schwarz-Schampera. 2009. Preliminary characterization and biological reduction of putative biogenic iron oxides (BIOS) from the Tonga-Kermadec Arc, Southwest Pacific Ocean. Geobiology 7:35–49.
36. Lavelle, J.W., and C. Mohn. 2010. Motion, commotion, and biophysical connections at deep ocean seamounts. Oceanography 23(1):90–103.
37. Mori, K., A. Maruyama, T. Urabe, K. Suzuki, and S. Hanada. 2008. Archaeoglobus infectus sp. nov., a novel thermophilic, chemolithoheterotrophic archaeon isolated from a deep-sea rock collected at Suiyo Seamount, Izu-Bonin Arc, western Pacific Ocean. International Journal of Systematic and Evolutionary Microbiology 58:810–816.
38. Mottl, M.J., S.C. Komor, P. Fryer, and C.L. Moyer. 2003. Deep-slab fluids fuel extremophilic Archaea on a Mariana forearc serpentinite mud volcano: Ocean Drilling Program Leg 195. Geochemistry, Geophysics, Geosystems 4(11), 9009, http://10.1029/2003GC000588.
39. Mottl, M.J., C.G. Wheat, P. Fryer, J. Gharib, and J.B. Martin. 2004. Chemistry of springs across the Mariana forearc shows progressive devolatilization of the subducting plate. Geochimica et Cosmochimica Acta 68:4,915–4,933.
40. Moyer, C.L., and J.J. Engebretson. 2002. Colonization by pioneer populations of epsilon-Proteobacteria and community succession at mid-ocean ridge hydrothermal vents as determined by T-RFLP analysis. Eos, Transactions, American Geophysical Union, Fall Meeting Supplement, 83, Abstract V11C-12.
41. Moyer, C.L., F.C. Dobbs, and D.M. Karl. 1995. Phylogenetic diversity of the bacterial community from a microbial mat at an active, hydrothermal vent system, Loihi Seamount, Hawaii. Applied and Environmental Microbiology 61:1,555–1,562.
42. Nakagawa, S., and K. Takai. 2008. Deep-sea vent chemoautotrophs: Diversity, biochemistry and ecological significance. FEMS Microbiology Ecology 65:1–14.
43. Nakagawa, S., K. Takai, K. Horikoshi, and Y. Sako. 2003. Persephonella hydrogeniphila sp. nov., a novel thermophilic, hydrogen-oxidizing bacterium from a deep-sea hydrothermal vent chimney. International Journal of Systematic and Evolutionary Microbiology 53:863–869.
44. Nakagawa, T., K. Takai, Y. Suzuki, H. Hirayama, U. Konno, U. Tsunogai, and K. Horikoshi. 2006. Geomicrobiological exploration and characterization of a novel deep-sea hydrothermal system at the TOTO caldera in the Mariana Volcanic Arc. Environmental Microbiology 8:37–49.
45. Parkes, R.J., B.A. Cragg, and P. Wellsbury. 2000. Recent studies on bacterial populations and processes in subseafloor sediments: A review. Hydrogeology Journal 8:11–28.
46. Rassa, A.C., S.M. McAllister, S.A. Safran, and C.L. Moyer. 2009. Zeta-Proteobacteria dominate the colonization and formation of microbial mats in low-temperature hydrothermal vents at Loihi Seamount, Hawaii. Geomicrobiology Journal 26:623–638.
47. Rhodes, J.M., C. Morgan, and R.A. Liias. 1990. Geochemistry of Axial Seamount lavas: Magmatic relationship between the Cobb Hotspot and the Juan de Fuca Ridge. Journal of Geophysical Research 95:12,713–12,733.
48. Staudigel, H., and D.A. Clague. 2010. The geological history of deep-sea volcanoes: Biosphere, hydrosphere, and lithosphere interactions. Oceanography 23(1):58–71.
49. Staudigel, H., H. Furnes, N. McLoughlin, N.R. Banerjee, L.B. Connell, and A. Templeton. 2008. 3.5 billion years of glass bioalteration: Volcanic rocks as a basis for microbial life? Earth-Science Reviews 89:156–176.
50. Staudigel, H., S.R. Hart, A. Pile, B.E. Bailey, E.T. Baker, S. Brooke, D.P. Connelly, L. Haucke, C.R. German, I. Hudson, and others. 2006. Vailulu’u Seamount, Samoa: Life and death on an active submarine volcano. Proceedings of the National Academy of Sciences of the United States of America 103:6,448–6,453.
51. Staudigel, H., C.L. Moyer, M.O. Garcia, A. Malahoff, D.A. Clague, and A.A.P. Koppers. 2010. Spotlight 3: Lō`ihi Seamount. Oceanography 23(1):72–73.
52. Stoffers, P., T.J. Worthington, U. Schwarz-Schampera, M.D. Hannington, G.J. Massoth, R. Hekinian, M. Schmidt, L.J. Lundsten, L.J. Evans, R. Vaiomo’unga, and T. Kerby. 2006. Submarine volcanoes and high-temperature hydrothermal venting on the Tonga arc, Southwest Pacific. Geology 34:453–456.
53. Stott, M.B., J.A. Saito, M.A. Crowe, P.F. Dunfield, S. Hou, E. Nakasone, C.J. Daughney, A.V. Smirnova, B.W. Mountain, K. Takai, and M. Alam. 2008. Culture-independent characterization of a novel microbial community at a hydrothermal vent at Brothers Volcano, Kermadec arc, New Zealand. Journal of Geophysical Research 113, B08S06, http://10.1029/2007JB005477.
54. Sudek, L.A., A.S. Templeton, B.M. Tebo, and H. Staudigel. 2009. Microbial ecology of Fe (hydr)oxide mats and basaltic rock from Vailulu’u Seamount, American Samoa. Geomicrobiology Journal 26:581–596.
55. Sunamura, M., Y. Higashi, C. Miyako, J. Ishibashi, and A. Maruyama. 2004. Two Bacteria phylotypes are predominant in the Suiyo Seamount hydrothermal plume. Applied and Environmental Microbiology 70:1,190–1,198.
56. Takai, K., C.L. Moyer, M. Miyazaki, Y. Nogi, H. Hirayama, K.H. Nealson, and K. Horikoshi. 2005. Marinobacter alkaliphilus sp. nov., a novel alkaliphilic bacterium isolated from subseafloor alkaline serpentine mud from Ocean Drilling Program Site 1200 at South Chamorro Seamount, Mariana Forearc. Extremophiles 9:17–27.
57. Takai, K., S. Nakagawa, A.-L. Reysenbach, J. Hoek. 2006. Microbial ecology of mid-ocean ridges and back-arc basins. Pp. 185–213 in Back-Arc Spreading Systems: Geological, Biological, Chemical, and Physical Interactions. D.M. Christie, C.R. Fisher, S.M. Lee, and S. Givens, eds, Geophysical Monograph Series 166, American Geophysical Union, Washington, DC.
58. Takai, K., S. Nakagawa, Y. Sako, and K. Horikoshi. 2003. Balnearium lithotrophicum gen. nov., sp. nov., a novel thermophilic, strictly anaerobic, hydrogen-oxidizing chemolithoautotroph isolated from a black smoker chimney in the Suiyo Seamount hydrothermal system. International Journal of Systematic and Evolutionary Microbiology 53:1,947–1,954.
59. Takai, K., K. Nakamura, T. Toki, U. Tsunogai, M. Miyazaki, J. Miyazaki, H. Hirayama, S. Nakagawa, T. Nunoura, and K. Horokoshi. 2008. Cell proliferation at 122°C and isotopically heavy CH₄ production by hyperthermophilic methanogen under high-pressure cultivation. Proceedings of the National Academy of Sciences of the United States of America 105:10,949–10,954.
60. Takai, K., T. Nunoura, K. Horikoshi, T. Shibuya, K. Nakamura, Y. Suzuki, M. Stott, G.J. Massoth, B.W. Christenson, C.E.J. deRonde, and others. 2009. Variability in microbial communities in black smoker chimneys at the NW caldera vent field, Brothers Volcano, Kermadec Arc. Geomicrobiology Journal 26:552–569.
61. Templeton, A.S., E.J. Knowles, D.L. Eldridge, B.W. Arey, A.C. Dohnalkova, S.M. Webb, B.E. Bailey, B.M. Tebo, and H. Staudigel. 2009. A seafloor microbial biome hosted within incipient ferromanganese crusts. Nature Geoscience 2:872–876.
62. Wessel, P., D.T. Sandwell, and S.-S. Kim. 2010. The global seamount census. Oceanography 23(1):24–33.
63. Wheat, C.G., P. Fryer, K. Takai, and S. Hulme. 2010. Spotlight 9: South Chamarro Seamount. Oceanography 23(1):174–175.
64. Wheat, C.G., H.W. Jannasch, J.N. Plant, C.L. Moyer, F.J. Sansone, and G.M. McMurty. 2000. Continuous sampling of hydrothermal fluids from Loihi Seamount after the 1996 event. Journal of Geophysical Research 105:19,353–19,367.
65. Wheat, C.G., M.J. Mottl, A.T. Fisher, D. Kadko, E.E. Davis, and E. Baker. 2004. Heat flow through a basaltic outcrop on a sedimented young ridge flank. Geochemistry, Geophysics, Geosystems 5(12), Q12006, http://10.1029/ 2004GC000700.
66. White, D.C., T.J. Phelps, and T.C. Onstott. 1998. What’s up down there? Current Opinion in Microbiology 1:286–290.
67. Whitman, W.B., D.C. Coleman, and W.J. Wiebe. 1998. Prokaryotes: The unseen majority. Proceedings of the National Academy of Sciences of the United States of America 95:6,578–6,583.

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