Adaptation of Rhizobium bacteria depends on the short- or long-term

effects of heavy metals

Borbala BIROBorbala BIRO

Laboratory of RhizobiologyLaboratory of Rhizobiology

Research Institute for Soil Science and Agricultural Chemistry

Hungarian Academy of SciencesHungarian Academy of Sciences (RISSAC)(RISSAC), Herman O ut 15, H-1022 , Herman O ut 15, H-1022

Budapest, Hungary. Budapest, Hungary. E-mail: E-mail: biro@rissac.hubiro@rissac.hu

Adaptation as a tool of sustainabilityAdaptation as a tool of sustainability

Adaptation - better tolerance of Adaptation - better tolerance of environmental (stress)factorsenvironmental (stress)factors

Adapted microbes confer their tolerance Adapted microbes confer their tolerance to the non-adapted plants (crops) – best to the non-adapted plants (crops) – best „„strugle for life strategystrugle for life strategy” of both ” of both partners!partners!

New generation of microbial inoculums? New generation of microbial inoculums? But how the adaptation developes?But how the adaptation developes? Do adapted microbes functioning Do adapted microbes functioning

well?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 ZnSO4

100 µM ZnSO4

500 µM ZnSO4

1 mM ZnSO4

Root-organ carrot inoculated with Glomus intraradices Sy167

Growth as a function of the applied rates!

Better growth at the 2nd ratio!

1µM ZnSO4100 µM ZnSO4

Hyphal biomass 80mg

500 µm

160mg

500 µm

Discrepances at metal effects!Double biomass, but low sporulation (reduced fertility?)!

Discrepancies between adaptation Discrepancies between adaptation and functioning (Summary)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 Altered other ecophysiological parameters

((sporulationsporulation, infection ability – , infection ability – effectivityeffectivity, N, N22--fixing or P-mobilising ability – fixing or P-mobilising ability – efficiencyefficiency))

In a multifactorial system any In a multifactorial system any parameters have his own „private life”parameters have his own „private life”Needs for modell experimental background!

Introduction and hypothesis NN22-fixing (bioferilizer) bacteria-fixing (bioferilizer) bacteria are are

important element of soil-fertility! important element of soil-fertility! Some Some adaptation is necessary in the polluted adaptation is necessary in the polluted soil soil (microbial inoculums)!(microbial inoculums)!

But! But! How the adaptation developes?How the adaptation developes?How the adaptation is depending on:How the adaptation is depending on: the affectingthe affecting periods? periods?oror the affecting the affecting doses? doses?

Materials and methods

Modell experiments:Modell experiments: Long-termLong-term ( (16 year16 year) application in ) application in

(Braunschweig field study with (Braunschweig field study with sewage sewage sludgesludge) )

Short-termShort-term ( (4-year4-year)pot experiment with )pot experiment with sludgesludge (RISSAC, Budapest) (RISSAC, Budapest)

Long-termLong-term, , only metal-salt only metal-salt experiment (experiment (13 13 metals, 4 dosesmetals, 4 doses) – (RISSAC, ) – (RISSAC, Nagyhörcsök) Nagyhörcsök)

Materials and methods

NN22-fixing -fixing Rhizobium Rhizobium strains:strains: Control (only fertilizer, no sludge, no Control (only fertilizer, no sludge, no

metals)metals)

Long(slow)-adapted strains (16-years) Long(slow)-adapted strains (16-years) Short(fast)-adapted (1.-, 4.-years Short(fast)-adapted (1.-, 4.-years

isolates)isolates)

Short-term effect of Zn-containing sewage sludge

0 7.5 15 30 60 t/ha

Studies on the root-nodulation an on the Rhizobium isolates

Rhizobium – Zn Long-(16-years)-adaptation

Adapted Rhizobium

40

60

80

100

120

140

160

180

0 1 2 3 4 5Concentrations

Rela

tive

grow

t (%

)

Non adapted Rhizobium

40

60

80

100

120

140

160

180

0 1 2 3 4 5Concentrations

Rela

tive

grow

th (%

)

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!

Rhizobium - CuLong-(16-years)-adaptation

Non adapted Rhizobium

0

20

40

60

80

100

120

140

0 1 2 3 4 5Concentrations

Rela

tive

grow

th (%

)

Adapted Rhizobium

0

20

40

60

80

100

120

140

0 1 2 3 4 5Concentrations

Relat

ive g

rowt

(%)

0 0.1 1 10 100 1000 mg.L-1

tolerantsensitive

Less dosis-dependence, better growth at highest rates

Rhizobium – Zn Short-(4-years)-adaptation

2000/Zn

4

6

8

10

12

14

kontrol 45 90 180 360 720Concentrations (mg.l-1)

LgCF

Uml-1

2002/Zn

4

6

8

10

12

14

kontrol 45 90 180 360 720Concentrations (mg.l-1)

LgCF

Uml-1

Zn become more toxic at the higher doses!

Tolerant Sensitive

Rhizobium – CrShort-(4-years)-adaptation)

Cr/2000

4

6

8

10

12

14

kontrol 37,5 75 150 300 600Concentrations (mg.l-1)

LgCF

Uml

-1

Cr/2002

4

6

8

10

12

14

kontrol 37,5 75 150 300 600Concentrations (mg.l-1)

LgCF

Uml-1

Cr become more toxic at the higher ratios!

tolerant sensitive

Summary Summary ShortShort and and longlong-term effect of metals-term effect of metals

A clear dosis-dependence was found! A clear dosis-dependence was found!

Slow releaseSlow release of below toxic levels of below toxic levels might might increse the adaptationincrese the adaptation to the toxic ratios! to the toxic ratios!

The adaptation is a The adaptation is a process in timeprocess in time and and might enhance the behaviour and „strugle might enhance the behaviour and „strugle for life” success of microbes! for life” success of microbes!

háttér-érték

tulajdonság

adaptáció toxikusság

növekvő stressz vagy szennyeződés

javuló tulajdonság

A környezeti alkalmazkodás folyamata

Adaptáció és szennyeződésAdaptation in timeAdaptation in time

Better tolerance for a certain limits!

Conclusion - I

Take care of the affecting doses! Take care of the affecting doses! The sensitivity is incresing at The sensitivity is incresing at

beyond-tolerable levels! beyond-tolerable levels!

Enhanced selection pressure on the Enhanced selection pressure on the population! population!

Conclusion - II

According to Puskin, According to Puskin, Minden az „Anyegin” Minden az „Anyegin” múlikmúlik” („things are highly dependent on ” („things are highly dependent on the the moneymoney”?)”?)

In our caseIn our case::

((It is a fortune, that microbe behaves differentlyIt is a fortune, that microbe behaves differently))

The adaptation success is highly The adaptation success is highly dependent on the:dependent on the:

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

Acknowledgement!

MTA TAKI for experimental background MTA TAKI for experimental background (Imre (Imre KÁDÁR, Tamás NÉMETH)KÁDÁR, Tamás NÉMETH)

Support of the Hung. Res. Fund (OTKA)Support of the Hung. Res. Fund (OTKA) Spanish, Swiss, Austrian, Russian – Spanish, Swiss, Austrian, Russian –

bilateral collaborationsbilateral collaborations Hungarian parners of studies (NyF, Hungarian parners of studies (NyF,

Nyiregyháza, SZIE, Gödöllő), Nyiregyháza, SZIE, Gödöllő),