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6 Functional Groups of Microrganisms<br />

of the Phosphorus Cycle<br />

4 Microorganisms on the Rhizosphere Microcosm 59<br />

The main functional groups of the phosphorus cycle are the mycorrhizal<br />

fungi and the inorganic phosphate solubiliser microorganisms. The interaction<br />

between these two microbial groups is fundamental for the nutrition of<br />

the majority of native <strong>plant</strong>s and is also of agronomic interest.<br />

The phosphate solubiliser functional group can include fungi, actinomycetes<br />

and bacteria that are capable of solubilizing inorganic phosphate by<br />

production and excretion of organic and inorganic acids, of a phosphatase<br />

group of enzymes and of carbon dioxide (CO 2) in the rhizosphere soil solution.<br />

Carbon dioxide can cause the solubilisation of calcium, magnesium and<br />

Heterotrophic<br />

Microorganisms<br />

Insoluble<br />

Inorganic<br />

Phosphate<br />

Nitrifying<br />

Bacteria<br />

CO2<br />

Organic<br />

Acids Soluble<br />

Inorganic<br />

Phosphate<br />

Mycorrhiza<br />

Fungi<br />

Plant<br />

Root<br />

Nitric Acid<br />

Sulfur Oxiding<br />

Sulfur Reducing<br />

H2SO4<br />

H2S<br />

Fig. 6. The activity of some functional groups of microorganisms in the phosphorus<br />

cycle

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