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A daptation of Rhizobium bacteria depends on the short- or long-term effects of heavy metals

A daptation of Rhizobium bacteria depends on the short- or long-term effects of heavy metals. Borbala BIRO Laboratory of Rhizobiology Research Institute for Soil Science and Agricultural Chemistry

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A daptation of Rhizobium bacteria depends on the short- or long-term effects of heavy metals

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  1. Adaptation of Rhizobium bacteria depends on the short- or long-term effects of heavy metals Borbala BIRO Laboratory of Rhizobiology Research Institute for Soil Science and Agricultural Chemistry Hungarian Academy of Sciences (RISSAC), Herman O ut 15, H-1022 Budapest, Hungary. E-mail: biro@rissac.hu

  2. Adaptation as a tool of sustainability • Adaptation - better tolerance of environmental (stress)factors • Adapted microbes confer their tolerance to the non-adapted plants (crops) – best „strugle for life strategy” of both partners! New generation of microbial inoculums? • But how the adaptation developes? • Do adapted microbes functioning well?

  3. 12 weeks old tomato plants grown in heavy metal soil with or without metal(Zn)-adapted mycorrhiza (Glomus sp. Br1) Inoculated Non-inoculated

  4. Discrepances at metal effects! Root-organ carrot inoculated with Glomus intraradices Sy167 1 µM ZnSO4 100 µM ZnSO4 Growth as a function of the applied rates! 500 µM ZnSO4 1 mM ZnSO4 Better growth at the 2nd ratio!

  5. Discrepances at metal effects! 160mg Double biomass, but low sporulation (reduced fertility?)! 100 µM ZnSO4 1µM ZnSO4 500 µm 500 µm 80mg Hyphal biomass

  6. Discrepancies between adaptation and functioning (Summary) Adaptation: • better metal tolerance! • enhanced growth even for the host-plant! But! • Altered other ecophysiological parameters (sporulation, infection ability – effectivity, N2-fixing or P-mobilising ability – efficiency) In a multifactorial system any parameters have his own „private life” Needs for modell experimental background!

  7. Introduction and hypothesis • N2-fixing (bioferilizer) bacteria are important element of soil-fertility! Some adaptation is necessary in the polluted soil (microbial inoculums)! But! How the adaptation developes? How the adaptation is depending on: • the affecting periods? or • the affecting doses?

  8. Materials and methods Modell experiments: • Long-term (16 year) application in (Braunschweig field study with sewage sludge) • Short-term (4-year)pot experiment with sludge (RISSAC, Budapest) • Long-term, only metal-salt experiment (13 metals, 4 doses) – (RISSAC, Nagyhörcsök)

  9. Materials and methods N2-fixing Rhizobium strains: • Control (only fertilizer, no sludge, no metals) • Long(slow)-adapted strains (16-years) • Short(fast)-adapted (1.-, 4.-years isolates)

  10. Short-term effect of Zn-containing sewage sludge 07.5 15 30 60 t/ha Studies on the root-nodulation an on the Rhizobium isolates

  11. Rhizobium – Zn Long-(16-years)-adaptation Stimulation Retardation 0 0.1 1 10 100 1000 mg.L-1 Zn become non-essential and less-dependent on the doses with a reduced growth-ability!

  12. Rhizobium - CuLong-(16-years)-adaptation tolerant sensitive 0 0.1 1 10 100 1000 mg.L-1 Less dosis-dependence, better growth at highest rates

  13. Rhizobium – Zn Short-(4-years)-adaptation Tolerant Sensitive Zn become more toxic at the higher doses!

  14. Rhizobium – CrShort-(4-years)-adaptation) tolerant sensitive Cr become more toxic at the higher ratios!

  15. Summary Short and long-term effect of metals A clear dosis-dependence was found! • Slow release of below toxic levels might increse the adaptation to the toxic ratios! • The adaptation is a process in time and might enhance the behaviour and „strugle for life” success of microbes!

  16. Adaptation in time Better tolerance for a certain limits!

  17. Conclusion - I Take care of the affecting doses! • The sensitivity is incresing at beyond-tolerable levels! • Enhanced selection pressure on the population!

  18. Conclusion - II According to Puskin, Minden az „Anyegin” múlik” („things are highly dependent on the money”?) In our case: (It is a fortune, that microbe behaves differently) The adaptation success is highly dependent on the: Affecting periods at a certain metal-type (Zn) at a certain metal doses!

  19. Acknowledgement! MTA TAKI for experimental background (Imre KÁDÁR, Tamás NÉMETH) • Support of the Hung. Res. Fund (OTKA) • Spanish, Swiss, Austrian, Russian – bilateral collaborations • Hungarian parners of studies (NyF, Nyiregyháza, SZIE, Gödöllő), Thank you for your attention!

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