30 Questions
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
When did the earliest recorded instance of commercialization of PGPB occur?
1895
What are some challenges associated with shipping wet inoculants for PGPB?
Expensive shipping costs, need for long-distance shipping if not produced locally
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.
What is the main challenge in regulating nitrogen fixation in plants?
There are no plant promoters that respond to the NifA protein.
Explain the consequence of increasing nitrogen fixation in terms of energy requirement.
Increasing nitrogen fixation increases the requirement of energy.
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.
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.
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.
How do siderophore-producing bacteria promote plant growth?
By supplying iron for plant utilization and removing iron from the environment of phytopathogens
What is the principal storage form of phosphorus in plants?
Inositol hexaphosphate (phytate)
What are the two main forms of insoluble phosphorus in soil?
Inorganic and organic forms
What is the role of phosphatases in plant growth?
To break down organic phosphorus compounds like phosphomonoesters and phosphotriesters
Which minerals are considered inorganic forms of phosphorus in soil?
Minerals such as Apatite
How is Apatite commonly used in agriculture?
Ground into a powder and used as a fertilizer as a source of phosphorus
What are the characteristics of bacterial shape as described in the text?
Rod, spherical, spiral, or filamentous
How do filamentous bacteria reproduce?
By producing spores called conidia at the end of the filament
What is the size range of bacteria in a young culture?
0.6 to 3.5 micrometers in diameter
What type of DNA do bacteria possess?
Chromosomal circular DNA and extra-chromosomal Plasmid DNA
What envelops the cell walls of most plant pathogenic bacteria?
Viscous, gummy material called slime layer (thin) and Capsule (thick)
What do Gram-negative bacteria have that Gram-positive bacteria do not?
An extra outer membrane
What is the function of the nitrogenase enzyme other than fixing nitrogen?
Reduce acetylene to ethylene
How are the nif genes arranged in bacteria like Rhizobia spp. and PGPB?
In a single cluster of ~24 kb with seven separate operons
What is the role of the NifA protein in nitrogen fixation?
It turns on the transcription of all nif operons except its own
How does the NifL protein regulate nitrogen fixation under unfavorable conditions?
It binds to NifA to block its activity
What happens to the transcription of nif genes in the presence of oxygen or high levels of fixed nitrogen?
It is turned off
Do all nitrogen-fixing organisms have a NifL protein?
No
Learn about the screening, isolation, and commercialization of Plant Growth-Promoting Bacteria (PGPB) as discussed by Bernard Glick. Explore the benefits of using PGPB in agriculture to enhance plant growth and yield. Understand the historical context and commercial applications of PGPB.
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