Skip to main content

Diversity and Activity of Microbes Oxidizing Methane and Ammonium in Northern Organic Soils under Changing Environmental Conditions

  • Chapter
Book cover Biotechnology for the Environment: Strategy and Fundamentals

Part of the book series: Focus on Biotechnology ((FOBI,volume 3A))

Abstract

Microbial methane and ammonium oxidation in soil has a great importance in the atmospheric gas composition. Peat soils, typical in northern latitudes, are major sources of atmospheric methane as a result of methane producing microbes they harbour. Only a part of the methane produced in anaerobic peat is emitted to atmosphere because of microbial methane oxidation in the uppermost aerobic peat profile. Lowering of water table e.g., for agricultural or forestry purposes, changes the relative activity of methane producing and oxidizing microbes. Drainage generally decreases methane emissions. Nitrogen-rich peat soils are potential sources of nitrous and nitric oxides. Microbes oxidizing ammonium are among the key organisms responsible for the production of nitrogenous oxides. In natural water-logged peat, the production of nitrous and nitric oxides is negligible because activities of nitrifying and denitrifying bacteria are low. Drainage of peat soils for agriculture largely increases decomposition of organic matter and activity of nitrifying and denitrifying bacteria. Among soil ecosystems, organic agricultural soils have the highest nitrous oxide production. Drainage for forestry also induces some nitrous oxide production, especially in the most nitrogen-rich sites. There is a risk that global warming will change the hydrology of northern peatlands and their methane and nitrous oxide dynamics because the microbial processes are closely associated to the hydrological characteristics of peatlands. The global importance of methane and ammonium oxidation in northern organic soils is known but the microbes responsible for these processes are poorly characterized. The isolation of these microbes has proven to be difficult, there are only few isolates. However, PCR amplification and sequencing of DNA extracted from natural and manipulated organic soils suggest a great diversity among these microbial populations. These studies are based on the gene sequences of 16S rDNA, or the genes encoding for the ammonia monooxygenase (AMO) of ammonium-oxidizing bacteria, and the methane monooxygenase (MMO) of methane-oxidizing microbes. The results obtained by molecular biological techniques strongly suggest that in acidic organic soils there are novel organisms responsible for ammonium and methane oxidation. The effect of environmental changes on the diversity of these microbes is unknown. Some recent results indicate that there are high similarities in microbial populations oxidizing ammonium and methane in various northern organic soils although their hydrological and nutritional conditions differ greatly.

This is a preview of subscription content, log in via an institution to check access.

Access this chapter

Chapter
USD 29.95
Price excludes VAT (USA)
  • Available as PDF
  • Read on any device
  • Instant download
  • Own it forever
eBook
USD 39.99
Price excludes VAT (USA)
  • Available as EPUB and PDF
  • Read on any device
  • Instant download
  • Own it forever
Softcover Book
USD 54.99
Price excludes VAT (USA)
  • Compact, lightweight edition
  • Dispatched in 3 to 5 business days
  • Free shipping worldwide - see info

Tax calculation will be finalised at checkout

Purchases are for personal use only

Institutional subscriptions

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  • Allison, S.M., and Prosser, J.I. (1991) Urease activity in neutrophilic autotrophic ammonia-oxidizing bacteria isolated from acid soils, Soil Biol. Biochem. 23, 45–51.

    Article  CAS  Google Scholar 

  • Aim, J., Saarnio, S., Nykanen, H., Silvola, J., and Martikainen, P.J. (1999) Winter CO2, CH4 and N2O fluxes on some natural and drained boreal peatlands, Biogeochemistry 44, 163–186.

    Google Scholar 

  • Amaral, J.A., and Knowles R. (1997) Inhibition of methane consumption in forest soils and pure cultures of methanotrophs by aqueous forest soil extracts, Soil Biol. Biochem. 29, 1713–1720.

    Article  CAS  Google Scholar 

  • Bartlett, K.R., Harriss, R.C. (1993) Review and assessment of methane emissions from wetlands, Chemosphere 26, 261–320.

    Article  CAS  Google Scholar 

  • Bender, M. and Conrad, R (1992) Kinetics of CH4 oxidation in oxic soils exposed to ambient air or high CH4 mixing ratios, FEMS Microbiol. Ecol. 101, 261–270.

    CAS  Google Scholar 

  • Bender, M. and Conrad, R. (1994) Methane oxidation activity in various soils and freshwater sediments: occurrence, characteristics, vertical profiles, and distribution on grain size fractions, J. Geophys. Res. 99, 16531–16540.

    Article  CAS  Google Scholar 

  • Benstead, J., King, M. and Williams, H.G. (1998) Methanol promotes atmospheric methane oxidation by methanotrophic cultures and soils, Appl. Environ. Microbiol 64, 1091–1098.

    PubMed  CAS  Google Scholar 

  • Bodelier, P.L.F., and Frenzel, P. (1999) Contribution of methanotrophic and nitrifying bacteria to CH4 and NH4 oxidation in the rhizosphere of rice plants as determined by new methods of discrimination, Appl. Environ. Microbiol. 65, 1826–1832.

    PubMed  CAS  Google Scholar 

  • Bruns, M.A., Stephen, J.R., Kowalchuk, G.A., Prosser, J.I., and Paul, E.A. (1999). Comparative diversity of ammonia oxidizer 16S rRNA gene sequences in native, tilled, and successional soils, Appl. Environ. Microbiol. 65, 2994–3000.

    PubMed  CAS  Google Scholar 

  • Bull, I.D., Parekh, N.R., Hall, G.H., Ineson, P. and Evershed, R.P. (2000) Detection and classification of atmospheric methane oxidizing bacteria in soil, Nature 405, 175–178.

    Article  PubMed  CAS  Google Scholar 

  • Clymo, R.S. (1992) Models of peat growth, in H. Vasander and M. Starr (eds.), SUO, Mires and peat 4, 127–136, Proceedings of the International Workshop, Hyytiala., Finland, 28 September — 1 October 1992. Finnish Peatland Society.

    Google Scholar 

  • Crill, P.M. (1991) Seasonal patterns of methane uptake and carbon dioxide release by a temperate woodland soil, Global Biogeochem. Cycles 5, 319–334.

    Article  CAS  Google Scholar 

  • Crill, P., Martikainen, P.J., Nykanen, H., and Silvola, J. (1994) Temperature and N fertilization effects on methane oxidation in a drained peatland soil, Soil Biol. Biochem 26, 1331–1339.

    Article  CAS  Google Scholar 

  • Davidson, E.A. (1991) Fluxes of nitrous oxide and nitric oxide from terrestrial ecosystems, in J.E. Rogers and W.B. Whitman (eds), Microbial Production and Consumption of Greenhouse Gases: Methane, Nitrogen Oxides and Halomethanes, American Society for Microbiology, Washington, D.C., pp. 219–235.

    Google Scholar 

  • De Boer, W., Duyts, H. and Laanbroek, H.J. (1989) Urea stimulated autotrophic nitrification in suspension of fertilized, acid heath soil, Soil Biol. Biochem. 21, 349–354

    Article  Google Scholar 

  • Dedysh, S.N., Panikov N.S., and Tiedje, J.M. (1998a) Acidophilic methanotrophic communities from sphagnum peat bogs, Appl. Environ. Microbiol. 64, 922–929.

    PubMed  CAS  Google Scholar 

  • Dedysh, S.N., Panikov, N., Liesack, W., Grosskopf, R., James, J.Z. and Tiedje, J.M. (1998b) Isolation of acidophilic methane-oxidizing bacteria from northern peat wetlands, Science 282, 281–284.

    Article  PubMed  CAS  Google Scholar 

  • Dobbie, K.E., Smith, K.A., Prieme, A., Christensen, S., Degorska, A., and Orlanski, P. (1996) Effect of land use on the rate of methane uptake by surface soils in northern Europe, Atmos. Environ. 30, 1005–1011.

    CAS  Google Scholar 

  • Dunfield, P. and Knowles, R. (1995) Kinetics of methane oxidation by nitrate, nitrite, and ammonium in a humisol, Appl. Environ. Microbiol. 61, 3129–3135.

    PubMed  CAS  Google Scholar 

  • Dunfield, P.F., Liesack, W., Henckel, T. Knowles, R. and Conrad, R. (1999) High affinity methane oxidation by a soil enrichment culture containing a type II methanotroph, Appl. Environ. Microbiol. 65, 1009–1014.

    PubMed  CAS  Google Scholar 

  • Freeman, C, Lock, M.A. and Reynolds, B. (1993). Fluxes of CO2, CH4 and N2O from a Welsh peatland following simulation of water table draw-dawn: Potential feedback to climatic change. Biogeochem. 19, 51–60.

    Article  Google Scholar 

  • Goldman, M.B., Groffman, P.M., Pouyat, R.V., McDonnell, M.J., and Pickett, S.T.A. (1995) CH4 uptake and N availability in forest soils along an urban to rural gradient, Soil Biol. Biochem. 27, 281–286.

    Article  CAS  Google Scholar 

  • Gorham, E. (1991) Northern peatlands: Role in the carbon cycle and probable responses to climatic warming, Ecol. Appl. 1, 182–195.

    Article  Google Scholar 

  • Hankinson, T.R., and Scmidt, E.L. 1984 Examination of an acid forest soil for ammonia-and nitrite-oxidizing autotrophic bacteria, Can. J. Microbiol. 30, 1125–1132.

    Article  CAS  Google Scholar 

  • Hastings, R.C., Ceccherine, M.T., Miclaus, N., Saunders, J.R., Bazzicalupo, M., McCarthy, A.J. (1997) Direct molecular biological analysis of ammonia oxidizing bacteria populations in cultivated soil plots treated with swine manure, FEMS Microbiol. Ecol. 23, 45–54.

    Article  CAS  Google Scholar 

  • Henckel, T., Jackel, U., Schnell, S., and Conrad, R. (2000) Molecular analyses of novel methanotrophic communities in forest soil that oxidize atmospheric methane, Appl. Environ. Microbiol. 66, 1801–1808.

    Article  PubMed  CAS  Google Scholar 

  • Holmes, A.J., Roslev, P., McDonald, I.R., Iversen, N., Henriksen, K., and Murrell, J.C. (1999). Characterization of methanotrophic bacterial populations in soils showing atmospheric methane uptake. Appl. Environ. Microbiol. 65, 3312–3318.

    PubMed  CAS  Google Scholar 

  • Hutsch, B.W., Webster, CP., and Powlson, D.S. (1994) Methane oxidation in soil as affected by land use, soil pH and N fertilization, Soil Biol. Biochem. 26, 1613–1622.

    Article  Google Scholar 

  • Jensen, S., Prieme, A., and Bakken, L. (1998) Methanol improves methane uptake in starved methanotrophic microorganisms, Appl. Environ. Microbiol. 64, 1143–1146.

    PubMed  CAS  Google Scholar 

  • Jiang, Q.Q., and Bakken L. (1999) Nitrous oxide production and methane oxidation by different ammonia.-oxidizing bacteria, Appl. Environ. Microbiol 65, 2679–2684.

    PubMed  CAS  Google Scholar 

  • Kettunen, A., Kaitala, V., Lehtinen, A., Lohila, A.L., Aim, J., Silvola, J., and Martikainen, P.J. (1999) Methane production and oxidation potentials in relation to water table fluctuations in two boreal mires, Soil. Biol. Biochem. 31, 1741–1749.

    Article  CAS  Google Scholar 

  • King, G. (1996) Regulation of methane oxidation: controls between anoxic sediments and oxic soils, in M.E. Lidstrom and F.R. Tabita (eds.), Microbial Growth on C1 Compounds, Kluwer Academic Publisher, Dordrecht, pp. 318–324.

    Chapter  Google Scholar 

  • King, G.M., Roslev, P., Skovgaard, H. (1990) Distribution and rate of methane oxidation in sediments of the Florida Everglades, Appl. Environ. Microbiol. 56, 2902–2911.

    PubMed  CAS  Google Scholar 

  • King G.M., and Schnell S. (1994a) Effect of increasing atmospheric methane concentration on ammonium inhibition of soil methane consumption, Nature 370, 282–284.

    Article  CAS  Google Scholar 

  • King, G.M., and Schnell, S. (1994b) Ammonium and nitrite inhibition of methane oxidation by Methylobacter albus BG8 and Methylosinus trichosporium OB3b at low methane concentration, Appl. Environ. Microbiol. 60, 3508–3513.

    PubMed  CAS  Google Scholar 

  • King, G.M., and Schnell, S. (1998) Effects of ammonium and non-ammonium salt additions on methane oxidation by Methylosinus trichosporium OB3b and Maine forest soils, Appl. Environ. Microbiol. 64, 253–257.

    PubMed  CAS  Google Scholar 

  • Klemedtsson, L., Jian, Q., Kasimir-Klemedtsson, A., and Bakken, L. (1999) Autotrophic ammoniumoxidizing bacteria in Swedish mor humus, Soil Biol. Biochem. 31, 839–847.

    Article  CAS  Google Scholar 

  • Kowalchuck, G.A., Stephen, J.R., De Boer, W., Prosser, J.I., Embley, T.M., and Woldendorp, J.W. (1997) Analysis of ammonia-oxidizing bacteria of the β subdivision of the class proteobacteria in coastal sand dunes by denaturing gradient gel electrophoresis and sequencing of PCR-amplified 16S ribosomal DNA fragments, Appl. Environ. Microbiol. 63, 1489–1497.

    Google Scholar 

  • Lång, K., Lehtonen, M., Martikainen, P.J. (1993). Nitrification potentials at different pH values in peat samples from various layers of a drained mire, Geomicobiol. J. 11, 141–147.

    Article  Google Scholar 

  • Lång, K., Silvola, J., Ruuskanen, J., and Martikainen, P.J. (1995) Emissions of nitric oxide from boreal peat soils, J. Biogeography, 22, 359–364.

    Article  Google Scholar 

  • Martikainen, P.J., and Nurmiaho-Lassila, E.-L. (1985) Nitrosospira, an important ammonium-oxidizing bacterium in fertilized coniferous forest soil, Can. J. Microbiol. 31, 190–197.

    Article  CAS  Google Scholar 

  • Martikainen, P.J., Nykanen, H., Crill, P., and Silvola, J. (1993) Effect of a lowered water table on nitrous oxide fluxes from northern peatlands, Nature 366, 51–53.

    Article  CAS  Google Scholar 

  • Manabe, S. and Wetherald, T.R. (1986) Reduction in summer soil wetness induced by an increase in atmospheric carbon dioxide, Science 232, 626–628.

    Article  PubMed  CAS  Google Scholar 

  • McDonald, I.R, Hall, G.M., Pickup, R.W., and Murrell, J.C. (1996) Methane oxidation potential and preliminary analysis of methanotrophs in blanket bog peat using molecular ecology techniques, FEMS Microbiol. Ecol. 21, 197–211.

    Article  CAS  Google Scholar 

  • McDonald, I.R., and Murrell, J.C. (1997) The particulate methane monooxygenase gene pmoA and its use as a functional gene probe for methanotrophs, FEMS Microbiol. Lett. 156, 205–210.

    Article  PubMed  CAS  Google Scholar 

  • Mendum, T.A., Sockett, R.E., and Hirsch, P.R. (1999) Use of molecular and isotopic techniques to monitor the response of autotrophic ammonia-oxidizing populations of the p subdivision of the class proteobacteria in arable soils to nitrogen fertilizer, Appl. Environ. Microbiol. 65, 4155–4162.

    PubMed  CAS  Google Scholar 

  • Mitchell, J.F.B. (1989) The “greenhouse effect” and climate change, Rev. Geophys 27, 115–139.

    Article  Google Scholar 

  • Nedwell, D.B. (1996) Methane production and oxidation in soils and sediments, in J.C. Murrell and D.P. Kelly (eds.), Microbiology of Atmospheric Trace Gases, NATO ASI Series I, Global Environmental Change, Springer-Verlag, Berlin, pp. 31–49.

    Google Scholar 

  • Nesbit, S.P., and Breitenbeck, G.A. (1992) A laboratory study of factors influencing methane uptake by soils. Agric. Ecosyst. Environ. 41, 39–54.

    Article  CAS  Google Scholar 

  • Nykänen, H., Aim, J., Lang, K. Silvola, J., and Martikainen, P.J. (1995) Emissions of CH4, N2O and CO2 from a virgin fen and fen drained for grassland in Finland, J. Biogeogr. 22, 351–357.

    Article  Google Scholar 

  • Nykänen, H., Vasander, H., Huttunen, J., and Martikainen, P.J. Dynamics of methane and nitrous oxide on ombrotrophic boreal peatland receiving experimental nitrogen load (submitted).

    Google Scholar 

  • Rangeley, A., and Knowles, R. (1988) Nitrogen transformation in a Scottish peat soil under laboratory conditions. Soil Biol. Biochem. 20, 385–391.

    Article  CAS  Google Scholar 

  • Regina, K. (1998) Microbial production of nitrous oxide and nitric oxide in boreal peatlands, PhD thesis, University of Joensuu Publications in Sciences 50, Joensuu, Finland.

    Google Scholar 

  • Regina, K., Nykanen, H., Silvola, J., and Martikainen, P.J. (1996) Fluxes of nitrous oxide from boreal peatlands as affected by peatland type, water table level and nitrification capacity, Biogeochemistry 35, 401–418.

    Article  CAS  Google Scholar 

  • Regina, K., Silvola, K., and Martikainen, P.J. (1998a) Mechanisms of N2O and NO production in the soil profile of a drained and forested peatland, as studied with acetylene, nitrapyrin and dimethylether. Biol. Fertil. Soil 27, 205–210.

    Article  CAS  Google Scholar 

  • Regina, K., Nykanen, H., Maljanen, M, Silvola, J. and Martikainen, P.J. (1998b) Emissions of N2O and NO and net nitrogen mineralisation in a boreal forested peatland treated with different nitrogen compounds, Can. J. Forestry 28, 132–140.

    Article  CAS  Google Scholar 

  • Regina, K., Silvola, J., and Martikainen, P.J. (1999) Short-term effects of changing water table on N2O fluxes from peat monoliths from natural and drained boreal peatlands, Global Change Biol. 5, 183–189.

    Article  Google Scholar 

  • Roslev, P., and King G.M. (1994) Survival and recovery of methanotrophic bacteria starved under oxic and anoxic conditions, Appl. Environ. Microbiol. 60, 2602–2608.

    PubMed  CAS  Google Scholar 

  • Roslev, P. and King G.M. (1995) Aerobic and anaerobic starvation metabolism in methanotrophic bacteria, Appl. Environ. Microbiol. 61, 1563–1570.

    PubMed  CAS  Google Scholar 

  • Roslev, P., Iversen, N. and Henriksen, K. (1997) Oxidation and assimilation of atmospheric methane by soil methane oxidizers, Appl. Environ. Microbiol. 63, 874–880.

    PubMed  CAS  Google Scholar 

  • Rosswal, T., and Granhall, U. (1980) Nitrogen cycling in a subarctic ombrotrophic mire, Ecol. Bull. 30, 209–234.

    Google Scholar 

  • Roulet, N.T., Ash, R., Quinton W., and Moore T. (1993) Methane flux from drained northern peatlands: Effect of persistent water table lowering on flux, Global Biogeochem. Cycles 7, 749–769.

    Article  CAS  Google Scholar 

  • Saari, A., Martikainen, P.J., Ferm, A., Ruuskanen, J., De Boer, W., Troelstra, S.R., and Laanbroek, H. (1997) Methane oxidation in soil profiles of Dutch and Finnish coniferous forests with different soil texture and atmospheric nitrogen deposition, Soil Biol. Biochem. 29, 1625–1632.

    Article  CAS  Google Scholar 

  • Saarnio, S., and Silvola, J. (1999) Effects of increased CO2 and N on CH4 efflux from a boreal mire: a growth chamber experiment, Oecologia 119, 349–356.

    Article  Google Scholar 

  • Schimel, J.P. (1995) Plant transport and methane production as controls on methane flux from arctic wet meadow tundra, Biogeochemistry 2, 183–200.

    Article  Google Scholar 

  • Schnell, S., and King, G.M. (1994) Mechanistic analysis of ammonium inhibition of atmospheric methane consumption in forest soils, Appl. Environ. Microbiol. 60, 3514–3521.

    PubMed  CAS  Google Scholar 

  • Sitaula, B.K., Bakken, L., and Abrahamsen, G. (1995) CH4 uptake by temperate forest soil: Effect of N input and soil acidifcation, Soil Biol. Biochem. 27, 871–880.

    Article  CAS  Google Scholar 

  • Stephen, J.R., McCaig, A.E., Smith, Z., Prosser, J.I, and Embley, T.M. (1996) Molecular diversity of soil and marine 16S rRNA gene sequences related to p-subgroup ammonia-oxidizing bacteria, Appl. Environ. Microbiol. 62, 4147–4154.

    PubMed  CAS  Google Scholar 

  • Stephen, JR., Kowalchuck, G.A., Bruns, M.-A.V., McCaig, A.E., Phillips, C.J., Embley, T.M., and Prosser, J.I. (1998) Analysis of P-subgroup proteobacterial ammonia oxidizer populations in soil by denaturing gradient gel electrophoresis analysis and hierarchical phylogenetic probing, Appl. Environ. Microbiol. 64, 2958–2965.

    PubMed  CAS  Google Scholar 

  • Sundh, I., Nilsson, M., Granberg, G., and Svensson, B.H. (1994) Depth distribution of microbial production and oxidation of methane in northern boreal peatlands, Microb. Ecol. 27, 253–265.

    Article  CAS  Google Scholar 

  • Sundh, I., Mikkela, C, Nilsson, M., and Svensson, B.H. (1995) Potential aerobic methane oxidation in a Sphagnum-dominated peatland — Controlling factors and relation to methane emission, Soil Biol. Biochem., 27, 829–837.

    Article  Google Scholar 

  • Svensson, B.H. (1996) Contribution of microbial processes to global change, in J.C. Murrell and D.P. Kelly (eds.), Microbiology of Atmospheric Trace Gases, NATO ASI Series I, Global Environmental Change, Springer-Verlag, Berlin, pp. 255–259.

    Google Scholar 

  • Torn, M.S., and Chapin, F.S. (1993) Environmental and biotic controls over methane flux from arctic tundra, Chemosphere 26, 357–368.

    Article  CAS  Google Scholar 

  • Utaker, J.B., Bakken, L., Jian, Q.Q., and Nes, I.E. (1995) Phylogenetic analysis of seven new isolates of ammonium-oxidizing bacteria based on 16S rRNA gene sequences, System. Appl. Microbiol 18, 549–559.

    Article  Google Scholar 

  • Vasander, H., Laiho R., and Laine, J. (1997) Changes is species diversity in peatlands drained for forestry, in C.C. Tretti, M.F. Jurgensen, D.E. Grigal, M.R. Gale, and J.K. Jeglum (eds.), Northern Forested Wetlands: Ecology and Management, CRC Lewis Publisher, Boca Raton, pp. 109–119.

    Google Scholar 

  • Vasara, R., Suutari, M.H., Lipponen, M.T.T., Martikainen, P.J., Regina, K., Tuomainen, J., Kangasjarvi, J. and Servomaa, K. The diversity of ammonia-oxidizing and methane-oxidizing microbial populations in natural and manipulated northern organic soils (submitted).

    Google Scholar 

  • West, A.E., and Schmidt, S.K. (1999) Acetate stimulates CH4 oxidation by an alpine tundra soil, Soil Biol. Biochem 31, 1649–1655.

    Article  CAS  Google Scholar 

  • Willison, T.W., Webster, C.P., Goulding, K.W.T., and Powlson, D.S. (1995) Methane oxidation in temperate soils: Effects of land use and the chemical form of nitrogen fertilizer. Chemosphere 30, 539–546.

    Article  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Editor information

Editors and Affiliations

Rights and permissions

Reprints and permissions

Copyright information

© 2002 Springer Science+Business Media Dordrecht

About this chapter

Cite this chapter

Martikainen, P.J., Vasara, R.E., Lipponen, M.T., Tuomainen, J., Suutari, M.H., Servomaa, K. (2002). Diversity and Activity of Microbes Oxidizing Methane and Ammonium in Northern Organic Soils under Changing Environmental Conditions. In: Agathos, S.N., Reineke, W. (eds) Biotechnology for the Environment: Strategy and Fundamentals. Focus on Biotechnology, vol 3A. Springer, Dordrecht. https://doi.org/10.1007/978-94-010-0357-5_3

Download citation

  • DOI: https://doi.org/10.1007/978-94-010-0357-5_3

  • Publisher Name: Springer, Dordrecht

  • Print ISBN: 978-94-010-3907-9

  • Online ISBN: 978-94-010-0357-5

  • eBook Packages: Springer Book Archive

Publish with us

Policies and ethics