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Siderophores produced by bioagents in controlling of plant diseases

PL PATH 515

Submitted By;

Manjunatha o

M.Sc.Agri

Submitted to;

Dr.Bharati N Bhat

Sr, scientist Plant Pathology

SRTC Hyderabad -30

Contents

Iron – An Important Element Siderophores Siderophores of bacteria Case study How siderophores will form??? Role of siderophores in controlling

plant pathogens Bacteria used as BCA Conclusion Refereces

Iron – An Important Element

4th most abundant element in the world

An important nutrient for the body.

Helps with growth and development in the body, especially in children.

Iron is forever cycled from a liver storehouse in a protein called ferritin.

Lack “iron” in such an

iron-abundant planet ?

The Paradox of the Limited

Abundance of Iron

•Extremely limited bioavailability.

•Bacteria battles to acquire iron to obtain nutrients that to help contribute

to growth

Siderophores Siderophores is a Greek word means "iron carrier”.

They are small, high-affinity iron chelating compounds secreted by micro organisms such as bacteria, fungi and grasses .

Siderophores are amongst the strongest soluble Fe3+ binding agents known.

Siderophores usually form a stable, hexadentate, octahedral complex with Fe3+

Kloepper et al.(1980) were the first to demonstrate the imp. of Siderophores

Structure

Siderophores are amongst the strongest binders to Fe3+ known, with enterobactin being one of the strongest of these.

Siderophores are produced by both pathogenic and non-pathogenic bacteria in different environments.

Siderophores can be defined as small peptidicmolecules containing side chains and functional groups that can provide a high-affinity set of ligands to coordinate ferric ions .

Siderophores of bacteria

Pseudobactin

Pseudomonas sp

Schizokein

Bacillus subtilis

Others

Pseudomonas fluorescens –

ferribactin

Pseudomonas cepacia -

cepabactin

Pseudomonas aeruginosa -

pyoverdin

Case study

Role of fluorescent

siderophore production in

biological control of pythium

ultimum by a pseudomonas

fluorescens strain

- Joyce E Loper

pseudomonas fluorescens migula strain 3551 isolated from cotton rhizosphere soil, cotton from seed colonization and pre-emergence damping off.

The role of fluorescent siderophore production by strain 3551 in antagonism against P. ultimum was investigated

14 non fluorescent (Flu-) Tn5 insertion mutants of P. fluorescens 3551 obtained following matings with E-coli SM 10

Strain 3551 grew on iron deficient

medium, whereas the 14 (Flu-

)derivative strains did not. These 2

strains evaluated for colonization by P.

ultimum.

3551 decreased the colonization of

cotton seed by P. ultimum and

increased the seedling emergence.

(Flu-) derivative strains did not.

Conclusion

fluorescent siderophore production by

pseudomonas fluorescens strain 3551

contributes, but did not account for all

of its antagonistic activity against P.

ultimum.

How siderophores will

form???

Iron is often insoluble (oxides,

hydroxides)

Cells produce siderophores

Iron binds to siderophore

complex

Siderophorebinds to

recognition site on cell

Iron is reduced(Fe3+ into Fe2+)

Iron is taken upby the cell.

Siderophore

Siderophore receptor site on cell

Outside the Cell

Inside the Cell

Fe3+

Siderophore receptor site on cell

Outside the Cell

Fe3+

Fe3+Inside the Cell

Siderophore receptor site on cell

Fe3+

Fe3+

Siderophore

Outside the Cell

Fe3+

Inside the Cell

Role of siderophores in

controlling plant pathogens

To satisfy nutritional requirements of iron, microorganisms have evolved highly specific pathways that employ low molecular weight iron chelators termed siderophores.

Siderophores are secreted to solubilize iron from their surrounding environments.

forming a complex ferric-siderophore that can move by diffusion and be returned to the cell surface.

Siderophores can chelate ferric ion with high affinity.

its solubilization and extraction from most mineral or organic complexes.

In aerobic conditions at physiological pH, the reduced ferrous (Fe2+) form is unstable.

Fe2+ is readily oxidized to the oxidized ferric (Fe3+) form.

Fe3+ occurs as a poorly soluble iron hydroxide basically unavailable to biological systems.

Bacteria used as BCA

Psuedomonas fluroscence

Psuedomonas putida

Bacillus subtilis :- Bacillibactin

Among most of the bacterial siderophoresstudied, those produced by pseudomonadsare known for their high affinity to the ferric ion.

The potent siderophore, pyoverdin, can inhibit the growth of bacteria and fungi that present less potent siderophores in iron-depleted media in vitro.

P. putida B10 strain against Fusarium oxysporum.

But this suppression was lost when the soil was replenished with iron, a condition that represses the production of iron chelators by microorganisms.

conclusion

Recent studies have demonstrated the

suppression of soil-borne fungal

pathogens through the release of iron-

chelating siderophores by fluorescent

pseudomonads, rendering it

unavailable to other organisms.

References

International Journal of Modern Plant

& Animal Sciences.

Department of Soils and Water

Resource Management, Faculty of

Agriculture, Rajarata University of Sri

Lanka.

The Society for Biotechnology, Japan.

Published by Elsevier B.V

Reviews Anderson, A. J., Tari, P. H., and Tepper, C. S. 1988. Genetic

studies on the role of an agglutinin in root colonization by Pseudomonas putida. Appl. Environ. Microbiol.

Anderson, A. J., Tari, P. H., and Tepper, C. S. 1988. Genetic studies on the role of an agglutinin in root colonization by Pseudomonas putida. Appl. Environ. Microbiol.

Tari, P.H., and Anderson, A. J. 1988. Fusarium wilt suppression and agglutinability of Pseudomonas putida. Appl. Environ. Microbiol.

Jacobsen, B. J., Zidack, N. K., and Larson, B. J. 2004. The role of Bacillus-based biological control agents in integrated pest management systems: Plant diseases. Phytopathology.

Kloepper J W, Ryu C M, Zhang S. (2004). Induce systemic resistance and promotionplant growth by Bacillus spp. Phytopathology.

Kloepper J W, Leong J, Teintze M, Schroth M N. (1980). Pseudomonas siderophores: A mechanism explaining disease suppression in soils. Current Microbiology.

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