Rhizobacteria
Encyclopedia
Rhizobacteria are root-colonizing bacteria
that form symbiotic relationships with many plants. The name comes from the Greek
rhiza, meaning root. Though parasitic varieties of rhizobacteria exist, the term usually refers to bacteria that form a relationship beneficial for both parties (mutualism). Such bacteria are often referred to as plant growth-promoting rhizobacteria, or PGPRs.
The mechanism by which PGPRs promote plant growth is not clearly understood, but it is believed to be by the production of siderophores, assimilation of minerals, production of phytohormones, and symbiotic nitrogen fixation. PGPR bacteria include Pseudomonas putida
, Azospirillum fluorescens, and Azospirillum lipoferum.
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. A notable exception is the use of rhizobial inoculants for legumes such as peas. Inoculation with PGPRs ensure efficient nitrogen fixation, and they have been employed in North American agriculture for over 100 years.
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
that form symbiotic relationships with many plants. The name comes from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
rhiza, meaning root. Though parasitic varieties of rhizobacteria exist, the term usually refers to bacteria that form a relationship beneficial for both parties (mutualism). Such bacteria are often referred to as plant growth-promoting rhizobacteria, or PGPRs.
The mechanism by which PGPRs promote plant growth is not clearly understood, but it is believed to be by the production of siderophores, assimilation of minerals, production of phytohormones, and symbiotic nitrogen fixation. PGPR bacteria include Pseudomonas putida
Pseudomonas putida
Pseudomonas putida is a gram-negative rod-shaped saprotrophic soil bacterium. Based on 16S rRNA analysis, P. putida has been placed in the P. putida group, to which it lends its name....
, Azospirillum fluorescens, and Azospirillum lipoferum.
Though microbial inoculants
Soil inoculant
Soil inoculants are bacteria or fungi that are added to soils in order to improve plant growth by either:*Freeing up soil nutrients for plant use.*Entering into symbiotic relationships with plant root systems....
can be beneficial for crops, they are not widely used in industrial agriculture
Industrial agriculture
Industrial farming is a form of modern farming that refers to the industrialized production of livestock, poultry, fish, and crops. The methods of industrial agriculture are technoscientific, economic, and political...
, as large-scale application techniques have yet to become economically viable. A notable exception is the use of rhizobial inoculants for legumes such as peas. Inoculation with PGPRs ensure efficient nitrogen fixation, and they have been employed in North American agriculture for over 100 years.