microbial mediated micro nutrient transformation in soil

1. Microbial Mediated
Micronutrient Transformation in
soil
Fe
Zn
Cu
Mo
Mn

2. • Plants require some elements in such minute or smaller
amounts that these element have been designated as
minor/trace element or Micro nutrient.
• Plants absorbed micronutrient in lower concentration ppm
level.
Micronutrient
Iron, Zinc, Copper, Manganese, Boron, Molybdenum, Nickel, Chloride

3. • Source- Goethite, Haematite, Magnetite, Limonite,
Olivine
• Forms of Fe- Ferrous & Ferric (Two oxidation state)
• Two fraction- Organic & mineral
• Sufficient range of Fe in plants : 50 – 250 ppm.
• Below 50 ppm – Deficiency appears young leaves-
Interveinal chlorosis.
• Above 250 ppm- Leaf bronzing.
Iron (Fe)

4. Fe in soil
Mineral Fe
• 4th most abundant element in earth crust 5%
• Solubility is low.
Soil solution
• Well drained , oxidised soil has a more Fe3+
• Water logged soil – More Fe2+

5. Iron bacteria (micro organisms) play a major role
in transformation
 Bacteria & fungi oxidise ferrous state to ferric
state.
Heterotrophic microorganism attacks soluble
organic Fe in to inorganic Fe salts.
Bacteria & fungi produce specific enzyme.
Transformation of iron in soil by
Micro organisms

6. Bacteria oxidise ferrous Fe to ferric Fe state which
precipitate as ferric hydroxide – Iron Bacteria
• Gallinonella
• Siderocapsa
• Siderosphaera
• Ferribacterium
• Naumanniela
• Sideromonas
• Ferro-bacillus
• Siderobacter
• Siderococus

7. • Obligate Chemoautotrophs- Capable of utilizing
energy released in the process of ferric hydroxide
formation.
(E.g) Gallionella ferruginea
Thiobacillus ferroxidans
Ferrobacillus ferroxidans
Classification

8. • Facultative Chemoautotrophs-Utilizing energy
derived in the process of ferric hydroxide formation
or from organic matter.
• (E,g) Leptothrix ochraceae
• Heterotrophs- Do not energy derived in the process
of ferric hydroxide formation but depend on
organic matter for nutrition.
• (E.g) Naumanniela

9. • Cyanophycea
• Volvocales
• Chlorococcales
• Eugleninaea
• Conjugales
Transform ferrous salts to ferric salt
Algae

11. • Source: Limestone, Sandstone.
• Forms: Zn2+
• Sufficient range of Zn in plants : 25 – 150 ppm
• Mineral: Zn in lithosphere is 80 ppm
• Soil solution: Depends on the soil pH . If pH is more
Zn2+ availability is more.
Zinc (Zn)

12. Two fraction
Organic- Small amount 0.01%- 0.05%
Inorganic- Source is Zinc sulphate- soluble in soil
Below and above the range cause Rosetting or clustering of
young leaves.
Young leaves become chlorotic spot.

13. • Omnipotent bacteria- Increase concentration of Zn
• Fungi also influence solubilize the mineral from of
Zn in soil by production of organic acids.
• Organic material increase the availability of micro
organisms in soil
• Increase the availability of Zn in soil
Transformation of Zinc in soil by
Micro organisms

14. • Several zinc solubilizing bacteria (ZSB)- Tropical
and temperate soils to provide plant available Zn.
(Hafeez et al., 2013).
• Gluconacetobacter – sugarcane.
• Bacillus, Pseudomonas - Soybean, rice and wheat
capable of solubilizing Zn. (Saravanan et al., 2011).
Omnipotent bacteria

15. Zinc solubilizing bacteria
• Pseudomonas
• Bacillus
• Gluconacetobacter
• Burkholderia
• Acinetobacter
• Serratia
• Flavobacter
• Enterobacter

16. Comparison
• ZSB
• ZSB soil bacteria,
able to solubilize the
inorganic Zn

17. • These ZSB strains produce variety of low molecular
weight organic acids, particularly gluconic acid,
dissolute the insoluble Zn
• Reduce the pH of the soil solution - increase the plant
available zinc (Hafeez et al., 2013).
• Zn-fertilizers - 1-5% use efficiency for most of the crops
• ZSB soil bacteria, able to solubilize the inorganic Zn and
thereby increase the bioavailability for crop assimilation.

18. • Source: Pyrolusite, Hausmannite, Manganite.
• Forms: Mn2+
• Sufficient range of plant: 20 – 500 ppm.
• Fraction: Solution, Exchangeable, Organic, Mineral
Manganese

19. Mineral Mn
• Mn is found in most Fe-Mg rocks- weathering of primary
mineral.
• Pyrolusite
• Manganite
Soil solution Mn:
• MnSO4 is the most common Mn sources in soil.
• Most common form Mn2+ - 90%.
• High pH- Solubility of Mn2+ is low

20. • Manganese transformation include bacteria, fungi and
yeasts.
• Bacteria – Leptothrix mobilis - aquatic environment-
oxidizing both iron, manganese. (Nelson et al. 1998)
• Oxidize manganous compounds to manganic oxides
(MnO.,) at pH values as low as 6 & some times below 6.
(Mulder 1964, Mulder and van Veen 1963).
Transformation of Manganese in soil
by Micro organisms

21. • Manganese oxidation by a mixture of two bacteria
Corynebacterium sp. Chromobacterium sp. has been
recorded by Bromfield and Skerman (1950)
• Roots of living plants may promote the solubilization of
MnO, by excreting organic acids or other compounds
stimulating bacterial activity.

22. • Source: Malachite, Cupric ferrite, Carbonates,
Silicates, Sulfates, Chlorides.
• Sufficient range in plants: 5 to 20 ppm.
• Forms: Cuprous (Cu+), Cupric (Cu2+)
Copper

23. • Availability of copper in soil related with the presence of
black organic humus.
• H2S forming microorganisms may be involved in copper
precipitation.
Transformation of Copper in soil by
Micro organisms

24. Copper precipitation by hydrogen-sulphide-
producing bacteria
• Clostridia, Proteus vulgaris, Escherichia coli - producing
H2S from sulphur-containing amino acids (cystine,
methionine, glutathion, etc.)- precipitate the Cu
• Sulphate-reducing bacteria- precipitate the Cu- Insoluble
form- Assimilatory sulfate reduction
• Sulfate-reducing bacteria are responsible - hydrogen
sulfide will react with metal ions to produce metal
sulphides. These metal sulphides- insoluble