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 Hungarian Academy of Sciences (RISSAC), Herman O ut 15, H-1022 Budapest, Hungary.

Adaptation as a tool of sustainability Adaptation - better tolerance of environmental (stress)factors 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! 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? But how the adaptation developes? Do adapted microbes functioning well? Do adapted microbes functioning well?

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

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

1µM ZnSO µM ZnSO 4 Hyphal biomass 80mg 500 µm 160mg 500 µm Discrepances at metal effects! Double biomass, but low sporulation (reduced fertility?)!

Discrepancies between adaptation and functioning (Summary) Adaptation: Adaptation: better metal tolerance! better metal tolerance! enhanced growth even for the host-plant! enhanced growth even for the host-plant! But! But! Altered other ecophysiological parameters (sporulation, infection ability – effectivity, N 2 - fixing or P-mobilising ability – efficiency) Altered other ecophysiological parameters (sporulation, infection ability – effectivity, N 2 - fixing or P-mobilising ability – efficiency) In a multifactorial system any parameters have his own „private life” In a multifactorial system any parameters have his own „private life” Needs for modell experimental background!

Introduction and hypothesis N 2 -fixing (bioferilizer) bacteria are important element of soil-fertility! Some adaptation is necessary in the polluted soil (microbial inoculums)! N 2 -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? the affecting periods?or the affecting doses? the affecting doses?

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

Materials and methods N 2 -fixing Rhizobium strains: Control (only fertilizer, no sludge, no metals) Control (only fertilizer, no sludge, no metals) Long(slow)-adapted strains (16-years) Long(slow)-adapted strains (16-years) Short(fast)-adapted (1.-, 4.-years isolates) Short(fast)-adapted (1.-, 4.-years isolates)

Short-term effect of Zn-containing sewage sludge t/ha Studies on the root-nodulation an on the Rhizobium isolates

Rhizobium – Zn Long-(16-years)-adaptation StimulationRetardation mg.L -1 Zn become non-essential and less-dependent on the doses with a reduced growth-ability!

Rhizobium - Cu Long-(16-years)-adaptation mg.L -1 tolerant sensitive Less dosis-dependence, better growth at highest rates

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

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

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

Adaptation in time Better tolerance for a certain limits!

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

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! Affecting periods at a certain metal- type (Zn) at a certain metal doses!

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