, Volume 64, Issue 1, pp 77–96 | Cite as

Enumeration of Fe(II)-oxidizing and Fe(III)-reducing bacteria in the root zone of wetland plants: Implications for a rhizosphere iron cycle

  • Johanna V. Weiss
  • David Emerson
  • Stephanie M. Backer
  • J. Patrick Megonigal


Iron plaque occurs on the roots of most wetland and submersed aquatic plant species and is a large pool of oxidized Fe(III) in some environments. Because plaque formation in wetlands with circumneutral pH has been largely assumed to be an abiotic process, no systematic effort has been made to describe plaque-associated microbial communities or their role in plaque deposition. We hypothesized that Fe(II)-oxidizing bacteria (FeOB) and Fe(III)-reducing bacteria (FeRB) are abundant in the rhizosphere of wetland plants across a wide range of biogeochemical environments. In a survey of 13 wetland and aquatic habitats in the Mid-Atlantic region, FeOB were present in the rhizosphere of 92% of the plant specimens collected (n = 37), representing 25 plant species. In a subsequent study at six of these sites, bacterial abundances were determined in the rhizosphere and bulk soil using the most probable number technique. The soil had significantly more total bacteria than the roots on a dry mass basis (1.4 × 109 cells/g soil vs. 8.6 × 107 cells/g root; p < 0.05). The absolute abundance of aerobic, lithotrophic FeOB was higher in the soil than in the rhizosphere (3.7 × 106/g soil vs. 5.9 × 105/g root; p < 0.05), but there was no statistical difference between these habitats in terms of relative abundance (∼1% of the total cell number). In the rhizosphere, FeRB accounted for an average of 12% of all bacterial cells while in the soil they accounted for < 1% of the total bacteria. We concluded that FeOB are ubiquitous and abundant in wetland ecosystems, and that FeRB are dominant members of the rhizosphere microbial community. These observations provide a strong rationale for quantifying the contribution of FeOB to rhizosphere Fe(II) oxidation rates, and investigating the combined role of FeOB and FeRB in a rhizosphere iron cycle.

Fe(II)-oxidizing bacteria Fe(III)-reducing bacteria Rhizosphere Wetland 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Armstrong W. 1964. Oxygen diffusion from the roots of some British bog plants. Nature 204: 801–802.Google Scholar
  2. Armstrong W. 1971. Radial oxygen loss from intact rice roots as affected by distance from the apex, respiration, and waterlogging. Physiol. Plantarum 25: 192–197.Google Scholar
  3. Armstrong W. 1979. Aeration in higher plants. In: Woolhouse H.W.W. (ed.), Advances in Botanical Research. Academic Press, London, pp. 226–332.Google Scholar
  4. Batty L.C., Baker A.J.M., Wheeler B.D. and Curtis C.D. 2000. The effect of pH and plaque on the uptake of Cu and Mn in Phragmites australis. Ann. Bot. 86: 647–653.Google Scholar
  5. Bodelier P.L.E., Duyts H., Blom C.W.P.M. and Laanbroek H.J. 1998. Interactions between nitrifying and denitrifying bacteria in gnotobiotic microcosms planted with the emergent macrophyte Glyceria maxima. FEMS Microbiol. Ecol. 25: 63–78.Google Scholar
  6. Brix H. and Schierup H. 1991. Soil oxygenation in constructed reed beds: the role of macrophyte and soil-atmosphere interface oxygen transport. In: Cooper P.F. and Findlater B.C. (eds), Constructed Wetlands in Water Pollution Control. Pergamon Press, Oxford, pp. 53–66.Google Scholar
  7. Chen C.C., Dixon J.B. and Turner F.T. 1980. Iron coatings on rice roots – mineralogy and quantity influencing factors. Soil Sci. Soc. Am. J. 44: 635–639.Google Scholar
  8. Chen C.C., Dixon J.B. and Turner F.T. 1980. Iron coatings on rice roots – morphology and models of development. Soil Sci. Soc. Am. J. 44: 1113–1119.Google Scholar
  9. Christensen K.K. and Sand-Jensen K. 1998. Precipitated iron and manganese plaques restrict root uptake of phosphorus in Lobelia dortmanna. Can. J. Bot. 76: 2158–2163.Google Scholar
  10. Conrad R. and Klose M. 1999. Anaerobic conversion of carbon dioxide to methane, acetate and propionate on washed rice roots. FEMS Microbiol. Ecol. 30: 147–155.Google Scholar
  11. Crowder A.A. and Macfie S.M. 1986. Seasonal deposition of ferric hydroxide plaque on roots of wetland plants. Can. J. Bot. 64: 2120–2124.Google Scholar
  12. Dannenberg S. and Conrad R. 1999. Effect of rice plants on methane production and rhizospheric metabolism in paddy soil. Biogeochemistry 45: 53–71.Google Scholar
  13. Darke A.K. and Walbridge M.R. 1994. Estimating non-crystalline and crystalline aluminum and iron by selectable dissolution in a riparian forest soil. Commun. Soil Sci. Plant Anal. 25: 2089–2101.Google Scholar
  14. Day P.R. 1965. Particle fractionation and particle size analysis. In: Black C.A. (ed.), Methods of Soil Analysis. American Society of Agronomy, Madison, Wisconsin, USA, pp. 545–566.Google Scholar
  15. Eaton A.D. and Franson M.A.H. 1995. Multiple-tube fermentation technique for members of the coliform group. In: Standard Methods for the Examination of Water and Wastewater. American Public Health Association, Washington, DC, USA, pp. 9–51.Google Scholar
  16. Emerson D. 2000. Microbial oxidation of Fe(II) and Mn(II) at circumneutral pH. In: Lovley D.R. (ed.), Environmental Microbe-Metal Interactions. ASM Press, Washington, DC, USA, pp. 31–52.Google Scholar
  17. Emerson D. and Moyer C. 1997. Isolation and characterization of novel iron-oxidizing bacteria that grow at circumneutral pH. Appl. Environ. Microb. 63: 4784–4792.Google Scholar
  18. Emerson D. and Revsbech N.P. 1994. Investigation of an iron-oxidizing microbial mat community located near Aarhus, Denmark – laboratory studies. Appl. Environ. Microbiol. 60: 4032–4038.Google Scholar
  19. Emerson D., Weiss J.V. and Megonigal J.P. 1999. Iron-oxidizing bacteria are associated with ferric hydroxide precipitates (Fe-plaque) on the roots of wetland plants. Appl. Environ. Microbiol. 65: 2758–2761.Google Scholar
  20. Faulkner S.P. 1994. Biogeochemistry of Iron and Manganese in Constructed Wetlands Receiving Coalmine Drainage. Duke University, Durham, NC, USA.Google Scholar
  21. Fisher H.M. and Stone E.L. 1991. Iron oxidation at the surfaces of slash pine roots from saturated soils. Soil Sci. Soc. Am. J. 55: 1123–1129.Google Scholar
  22. Flessa H. 1994. Plant-induced changes in the redox potential of the rhizospheres of the submerged vascular macrophytes Myriophyllum verticillatum and Ranunculus circinatus. Aquat. Bot. 47: 119–129.Google Scholar
  23. Giblin A.E. and Howarth R.W. 1984. Porewater evidence for a dynamic sedimentary iron cycle in salt marshes. Limnol. Oceanogr. 29: 47–63.Google Scholar
  24. Greipsson S. 1995. Effect of iron plaque on roots of rice on growth of plants in excess zinc and accumulation of phosphorus in plants in excess copper or nickel. J. Plant Nutr. 18: 1659–1665.Google Scholar
  25. Greipsson S. and Crowder A.A. 1992. Amelioration of copper and nickel toxicity by iron plaque on roots of rice (Oryza sativa). Can. J. Bot. 70: 824–830.Google Scholar
  26. Hanert H.H. 1992. The genus Siderocapsa (and other iron-and manganese-oxidizing eubacteria). In: Trüper H.G., Balows A., Dworkin M., Harder W. and Schleifer K.H. (eds), The Prokaryotes. 2nd edn. Vol. 4. Springer-Verlag, New York, NY, USA, pp. 4102–4113.Google Scholar
  27. Hansel C.M., Fendorf S., Sutton S. and Newville M. 2001. Characterization of iron plaque and associated metals on the roots of mine-waste impacted aquatic plants. Environ. Sci. Technol. 35: 3863–3868.Google Scholar
  28. Hauck S., Benz M., Brune A. and Schink B. 2001. Ferrous iron oxidation by denitrifying bacteria in profundal sediments of a deep lake (Lake Constance). FEMS Microbiol. Ecol. 37: 127–134.Google Scholar
  29. Hines M.E., Banta G.T., Giblin A.E., Hobbie J.E. and Tugel J.B. 1994. Acetate concentrations and oxidation in salt-marsh sediments. Limnol. Oceanogr. 39: 140–148.Google Scholar
  30. Howeler R.H. and Bouldin D.R. 1971. The diffusion and consumption of oxygen in submersed soils. Soil Sci. Soc. Am. P. 35: 202–208.Google Scholar
  31. Jacobson M.E. 1994. Chemical and biological mobilization of Fe(III) in marsh sediments. Biogeochemistry 25: 41–60.Google Scholar
  32. Johnson-Green P.C. and Crowder A.A. 1991. Iron-oxide deposition on axenic and non-axenic roots of rice seedlings (Oryza sativa). J. Plant Nutr. 14: 375–386.Google Scholar
  33. King G.M. and Garey M.A. 1999. Ferric iron reduction by bacteria associated with the roots of freshwater and marine macrophytes. Appl. Environ. Microbiol. 65: 4393–4398.Google Scholar
  34. Kirby C.S., Thomas H.M., Southam G. and Donald R. 1999. Relative contributions of abiotic and biological factors in Fe(II) oxidation in mine drainage. Appl. Geochem. 14: 511–530.Google Scholar
  35. Koch A.L. 1996. Growth measurement. In: Gerhardt P., Murray R.G.E. and Wood W.A. (eds), Methods for General and Molecular Bacteriology. ASM Press, Washington, DC, USA, pp. 257–260.Google Scholar
  36. Lovley D.R. 2000. Fe(III) and Mn(IV) Reduction. In: Lovley D.R. (ed.), Environmental Microbe-Metal Interactions. ASM Press, Washington, DC, USA, pp. 3–30.Google Scholar
  37. Lovley D.R., Roden E.E., Phillips E.J.P. and Woodward J.C. 1993. Enzymatic iron and uranium reduction by sulfate-reducing bacteria. Mar. Geol. 113: 41–53.Google Scholar
  38. Lunsdorf H., Brummer I., Timmis K.N. and Wagner-Dobler I. 1997. Metal selectivity of in situ microcolonies in biofilms of the Elbe River. J. Bacteriol. 179: 31–40.Google Scholar
  39. Macfie S.M. and Crowder A.A. 1987. Soil factors influencing ferric hydroxide plaque-formation on roots of Typha latifolia. Plant Soil 102: 177–184.Google Scholar
  40. Mason D.J., Shamnuganathan S., Mortimer F.C. and Gant V.A. 1998. A fluorescent gram stain for flow cytometry and epiflourescence microscopy. Appl. Environ. Microbiol. 64: 2681–2685.Google Scholar
  41. Mendelssohn I.A., Kleiss B.A. and Wakeley J.S. 1995. Factors controlling the formation of oxidized root channels – a review. Wetlands 15: 37–46.Google Scholar
  42. Mendelssohn I.A., Mckee K.L. and Patrick W.H. 1981. Oxygen deficiency in Spartina alterniflora roots – metabolic adaptation to anoxia. Science 214: 439–441.Google Scholar
  43. Michaud S.C. and Richardson C.J. 1989. Relative radial oxygen loss in five wetland plants. In: Hammer D.A. (ed.), Constructed Wetlands for Wastewater Treatment. Lewis Publishers, Chelsea, Michigan, USA, pp. 501–507.Google Scholar
  44. Nelson D.W. and Sommers L.E. 1982. Total carbon, organic carbon, and organic matter. In: Page A.L., Miller R.H. and Kenny D.R. (eds), Methods of Soil Analysis: Part 2 – Chemical and Microbiological Properties. Soil Science Society of America, Inc, pp. 539–579.Google Scholar
  45. Neubauer S.C., Emerson D. and Megonigal J.P. 2002. Life at the energetic edge: Kinetics of circumneutral iron oxidation by lithotrophic iron-oxidizing bacteria isolated from the wetland plant rhizosphere. Appl. Environ. Microbiol. 68: 3988–3995.Google Scholar
  46. Perret D., Gaillard J.F., Dominik J. and Atteia O. 2000. The diversity of natural hydrous iron oxides. Environ. Sci. Technol. 34: 3540–3546.Google Scholar
  47. Phillips E.J.P. and Lovley D.R. 1987. Determination of Fe(III) and Fe(II) in oxalate extracts of sediment. Soil Sci. Soc. Am. J. 51: 938–941.Google Scholar
  48. Phillips E.J.P., Lovley D.R. and Roden E.E. 1993. Composition of non-microbially reducible Fe(III) in aquatic sediments. Appl. Environ. Microbiol. 59: 2727–2729.Google Scholar
  49. Ratering S. and Schnell S. 2001. Nitrate-dependent iron(II) oxidation in paddy soil. Environ. Microbiol. 3: 100–109.Google Scholar
  50. Roden E.E. and Edmonds J.W. 1997. Phosphate mobilization in iron-rich anaerobic sediments: microbial Fe(III) oxide reduction versus iron-sulfide formation. Arch. Hydrobiol. 139: 347–378.Google Scholar
  51. Roden E.E. and Wetzel R.G. 1996. Organic carbon oxidation and suppression of methane production by microbial Fe(III) oxide reduction in vegetated and unvegetated freshwater wetland sediments. Limnol. Oceanogr. 41: 1733–1748.Google Scholar
  52. Sobolev D. and Roden E.E. 2001. Suboxic deposition of ferric iron by bacteria in opposing gradients of Fe(II) and oxygen at circumneutral pH. Appl. Environ. Microbiol. 67: 1328–1334.Google Scholar
  53. Sokal R.R. and Rohlf F.J. 1995. Biometry. The Principles and Practice of Statistics in Biological Research. W.H. Freeman and Company, New York.Google Scholar
  54. St-Cyr L., Fortin D. and Campbell P.G.C. 1993. Microscopic observations of the iron plaque of a submerged aquatic plant (Vallisneria americana Michx). Aquat. Bot. 46: 155–167.Google Scholar
  55. Stookey L.L. 1970. Ferrozine: A new spectrophotometric reagent for iron. Anal. Chem. 42: 779–781.Google Scholar
  56. Straub K.L. and Buchholz-Cleven B.E.E. 1998. Enumeration and detection of anaerobic ferrous iron-oxidizing, nitrate-reducing bacteria from diverse European sediments. Appl. Environ. Microbiol. 64: 4846–4856.Google Scholar
  57. Taylor G.J. and Crowder A.A. 1983. Use of the DCB technique for extraction of hydrous iron-oxides from roots of wetland plants. Am. J. Bot. 70: 1254–1257.Google Scholar
  58. Taylor G.J., Crowder A.A. and Rodden R. 1984. Formation and morphology of an iron plaque on the roots of Typha latifolia grown in solution culture. Am. J. Bot. 71: 666–675.Google Scholar
  59. Thamdrup B. 2000. Bacterial manganese and iron reduction in aquatic sediments. In: Advances in Microbial Ecology. Kluwer Academic/Plenum Publishers, New York, pp. 41–84.Google Scholar
  60. Trolldenier G. 1988. Visualization of oxidizing power of rice roots and of possible participation of bacteria in iron deposition. Z. Planz Bodenkunde 151: 117–121.Google Scholar
  61. van Bodegom P., Goudriaan J. and Leffelaar P. 2001. A mechanistic model on methane oxidation in a rice rhizosphere. Biogeochemistry 55: 145–177.Google Scholar
  62. van Bodegom P., Stams F., Mollema L., Boeke S. and Leffelaar P. 2001. Methane oxidation and the competition for oxygen in the rice rhizosphere. Appl. Environ. Microbiol. 67: 3586–3597.Google Scholar
  63. van der Nat F.J.W.A. and Middelburg J.J. 1998. Seasonal variation in methane oxidation by the rhizosphere of Phragmites australis and Scirpus lacustris. Aquat. Bot. 61: 95–110.Google Scholar

Copyright information

© Kluwer Academic Publishers 2003

Authors and Affiliations

  • Johanna V. Weiss
  • David Emerson
  • Stephanie M. Backer
  • J. Patrick Megonigal

There are no affiliations available

Personalised recommendations