This document discusses how siderophores produced by bioagents can help control plant diseases. Siderophores are small iron-chelating compounds secreted by microorganisms like bacteria and fungi to acquire iron. Certain bacteria, such as Pseudomonas fluorescens and Pseudomonas putida, produce siderophores that can suppress plant pathogens by limiting their available iron. The document examines a case study on how fluorescent siderophore production by P. fluorescens strain 3551 contributes to antagonism against the plant pathogen Pythium ultimum. In conclusion, releasing siderophores can suppress soil-borne fungal pathogens by making iron unavailable to them.

1. Cl
O
Siderophores produced by bioagents in
controlling of plant diseases

2. PL PATH 515
Submitted By;
Manjunatha o
M.Sc.Agri
Submitted to;
Dr.Bharati N Bhat
Sr, scientist Plant Pathology
SRTC Hyderabad -30

3. 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

4. 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.

5. The Paradox of the Limited
Abundance of Iron
Lack “iron” in such an
iron-abundant planet ?
•Extremely limited bioavailability.
•Bacteria battles to acquire iron to obtain nutrients that to help contribute
to growth

6. 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

7. 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 peptidic
molecules containing side chains and functional
groups that can provide a high-affinity set of
ligands to coordinate ferric ions .

8. Siderophores of bacteria
 Pseudobactin
Pseudomonas sp
 Schizokein
Bacillus subtilis

9. Others
 Pseudomonas fluorescens –
ferribactin
 Pseudomonas cepacia -
cepabactin
 Pseudomonas aeruginosa -
pyoverdin

10. Case study
Role of fluorescent
siderophore production in
biological control of pythium
ultimum by a pseudomonas
fluorescens strain
- Joyce E Loper

11.  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

12.  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.

13. Conclusion
 fluorescent siderophore production by
pseudomonas fluorescens strain 3551
contributes, but did not account for all
of its antagonistic activity against P.
ultimum.

14. How siderophores will
form???
Iron is often
insoluble
(oxides,
hydroxides)
Cells produce
siderophores
Iron binds to
siderophore
complex
Siderophore
binds to
recognition site
on cell
Iron is reduced
(Fe3+ into Fe2+)
Iron is taken up
by the cell.

15. Siderophore receptor site on cell
Siderophore
Outside the Cell
Inside the Cell
Fe3+

16. Siderophore receptor site on cell
Outside the Cell
Fe3+
Fe3+
Inside the Cell

17. Siderophore receptor site on cell
Fe3+
Fe3+
Siderophore
Outside the Cell
Fe3+
Inside the Cell

18. 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.

19.  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.

20. Bacteria used as BCA
 Psuedomonas fluroscence
 Psuedomonas putida
 Bacillus subtilis :- Bacillibactin

21.  Among most of the bacterial siderophores
studied, those produced by pseudomonads
are 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

22. 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.

23. 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

24. 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.

25. Any questions
?

26. THANK YOU