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Plant Growth-Promoting Bacteria

ACC Deaminase enzyme

Cleaves ACC to α-ketobutyrate


Precursor of ethylene

Way to lower levels of ethylene in plants

Use bacteria that produce ACC deaminase

How bacteria use ACC deaminase and lower levels of ethylene

Bacteria binds to seed coats or plant roots.
Isolates ACC and cleaves

ACC deaminase prevents

Inhibition of root elongation resulting in large healthy plants

Siderophores used to

Solubulize and sequester Iron from soil and provide to plant cells

Ethylene is synthesized by a plant

After environmental stress

ACC produced in response to flood in roots

Can't be converted to ethylene because of no O2.

When ACC in the roots can't be converted to ethylene because of flooding causing anoxic conditions...

ACC is transported up and kills the stem/leaves


Increasing Phosphorous availability

Used to increase phosphorous availability

Transformed bacteria express and secrete phytase

Transposons used to

Move genes into chromosome


Promoter for the tac operon (lac+trp)

Increases biocontrol activity


Solution to fear of antibiotics spreading to other bacteria

Transfer deficient derivative of plasmids


Unable to transfer genes

Enzymes that can degrade fungal cell walls


Biocontrol activity

Indirect promotion of plant growth when PGPB decrease or prevent damage

In order to use PGPB as a biocontrol agent

Must adhere to root surfaces to prevent incursion by pathogens

PGPB activities

Fix Nitrogen.
Sequester Iron.
Iron uptake.
Produce Phytohormones.
Reduce Ethylene.

Examples of how to increase the amount of Nitrogen that can be fixed

Inhibiting synthesis of rhizobial glycogen(modulating the level of O2 within the bacterial cell).
Preventing rhizobial synthesis of polymer poly-B-hydroxybutryrate, which normall acts as a C storage compound)


First small peak which increases plant enhances survival, second peak causes senescence or death

Hydrogenase converts

H2 generated by nitrogenase into H+ to increase efficiency of N. fixation

Other nitrogrenase function

Creates H2 using ATP

Examples of biocontrols

Enzymes that lyse fungal cell walls.
Engineer strains to be better root colonizers, more efficient at lowering ethylene levels, more active producers of antibiotics/enzymes

Direct stimulation by PGPB

N. fixation.
Phosphorous mineralization.
ACC Deaminase

Examples of phytohormones


Auxin, Cytokinin, and Gibberellin do what

Enhance stages of plant growth

One of the most abundant minerals on eart and essential requirement for living organisms


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