Rhizobacteria

Rhizobacteria are root-associated bacteria that can have a detrimental (parasitic varieties), neutral or beneficial effect on plant growth.

[3][failed verification] Endophytic relationships involve the PGPRs residing and growing within the host plant in the apoplastic space.

Creating and maintaining root nodules for rhizobacteria can cost between 12–25% of the plant's total photosynthetic output.

Phosphorus, a limiting nutrient for plant growth, can be plentiful in soil, but is most commonly found in insoluble forms.

[5] Though microbial inoculants can be beneficial for crops, they are not widely used in industrial agriculture, as large-scale application techniques have yet to become economically viable.

Inoculation with PGPRs ensures efficient nitrogen fixation, and they have been employed in North American agriculture for over 100 years.

These include motility, chemotaxis to seed and root exudates, production of pili or fimbriae, production of specific cell surface components, ability to use specific components of root exudates, protein secretion, and quorum sensing.

The generation of mutants altered in expression of these traits is aiding our understanding of the precise role each one plays in the colonization process.

[16] PGPRs enhance plant growth by direct and indirect means, but the specific mechanisms involved have not all been well characterized.

[19] PGPR that synthesize auxins, gibberellins and kinetins or that interfere with plant ethylene synthesis have been identified.

[22] Studies conducted on sugar beet crops found that some root-colonizing bacteria were deleterious rhizobacteria (DRB).

Inoculated seeds are more likely to establish large enough rhizobacterial populations within the rhizosphere to produce notable beneficial effects on the crop.

Kyselková et al 2015 find planting forage species known to encourage native rhizobacteria retards the spread within the soil of antibiotic resistance genes of cow faeces bacteria.