Beneficial Plant Bacterial Interaction by Bernard Glick

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What are some factors to consider when commercializing PGPB?

Rhizospheric versus endophytic, appropriate biological activity, non-pathogenic, easy to prepare, easy to ship and store, stable

What are wet inoculants in the context of PGPB commercialization?

Bacterial suspensions sold in 1-5 lit plastic bags

How are peat-based inoculants different from wet inoculants?

PGPB mixed with peat, stable for several years, support 10^9-10^10 bacterial cells per gram of peat

What is the purpose of using adhesives and polymers in peat-based inoculants?

To ensure good contact between the rhizobia and the legume seed coat Signup and view all the answers

When did the earliest recorded instance of commercialization of PGPB occur?

1895 Signup and view all the answers

What are some challenges associated with shipping wet inoculants for PGPB?

Expensive shipping costs, need for long-distance shipping if not produced locally Signup and view all the answers

Why is genetic engineering of plants with the entire nif gene cluster not effective for increasing nitrogen fixation?

Normal level of oxygen in the host cells would inactivate nitrogenase. Signup and view all the answers

What is the main challenge in regulating nitrogen fixation in plants?

There are no plant promoters that respond to the NifA protein. Signup and view all the answers

Explain the consequence of increasing nitrogen fixation in terms of energy requirement.

Increasing nitrogen fixation increases the requirement of energy. Signup and view all the answers

Why may a bacterium engineered to fix a higher level of nitrogen lose its effectiveness as a PGPB?

Diminished growth rate due to depleting the cell's ATP stores. Signup and view all the answers

Describe the complexity of nodulation in nitrogen fixation.

It requires the functioning of a large number of genes, some of which are highly conserved while others are species-specific. Signup and view all the answers

How do rhizobia utilize plant exudates as chemo-attractants?

Rhizobia move towards host plant-secreted nutrients that act as chemo-attractants to locate infection sites. Signup and view all the answers

How do siderophore-producing bacteria promote plant growth?

By supplying iron for plant utilization and removing iron from the environment of phytopathogens Signup and view all the answers

What is the principal storage form of phosphorus in plants?

Inositol hexaphosphate (phytate) Signup and view all the answers

What are the two main forms of insoluble phosphorus in soil?

Inorganic and organic forms Signup and view all the answers

What is the role of phosphatases in plant growth?

To break down organic phosphorus compounds like phosphomonoesters and phosphotriesters Signup and view all the answers

Which minerals are considered inorganic forms of phosphorus in soil?

Minerals such as Apatite Signup and view all the answers

How is Apatite commonly used in agriculture?

Ground into a powder and used as a fertilizer as a source of phosphorus Signup and view all the answers

What are the characteristics of bacterial shape as described in the text?

Rod, spherical, spiral, or filamentous Signup and view all the answers

How do filamentous bacteria reproduce?

By producing spores called conidia at the end of the filament Signup and view all the answers

What is the size range of bacteria in a young culture?

0.6 to 3.5 micrometers in diameter Signup and view all the answers

What type of DNA do bacteria possess?

Chromosomal circular DNA and extra-chromosomal Plasmid DNA Signup and view all the answers

What envelops the cell walls of most plant pathogenic bacteria?

Viscous, gummy material called slime layer (thin) and Capsule (thick) Signup and view all the answers

What do Gram-negative bacteria have that Gram-positive bacteria do not?

An extra outer membrane Signup and view all the answers

What is the function of the nitrogenase enzyme other than fixing nitrogen?

Reduce acetylene to ethylene Signup and view all the answers

How are the nif genes arranged in bacteria like Rhizobia spp. and PGPB?

In a single cluster of ~24 kb with seven separate operons Signup and view all the answers

What is the role of the NifA protein in nitrogen fixation?

It turns on the transcription of all nif operons except its own Signup and view all the answers

How does the NifL protein regulate nitrogen fixation under unfavorable conditions?

It binds to NifA to block its activity Signup and view all the answers

What happens to the transcription of nif genes in the presence of oxygen or high levels of fixed nitrogen?

It is turned off Signup and view all the answers

Do all nitrogen-fixing organisms have a NifL protein?

No Signup and view all the answers