The purB gene controls rhizosphere colonization by Pantoea agglomerans

Area of Science:

• Microbiology
• Plant-Microbe Interactions
• Molecular Biology

Background:

• Rhizosphere competence is vital for beneficial rhizobacteria.
• Transposon mutagenesis is a key tool for identifying genes involved in bacterial traits.

Purpose of the Study:

• To isolate and characterize a Pantoea agglomerans mutant defective in root colonization.
• To identify the specific gene responsible for impaired rhizosphere competence.

Main Methods:

• Transposon (Tn5) mutagenesis of Pantoea agglomerans NBRISRM.
• Root colonization assays in a sand-nonsterilized soil system.
• Southern hybridization and DNA sequencing to identify the Tn5 insertion site.

Main Results:

• One mutant, SRMT, exhibited a 6-log unit decrease in root colonization compared to the wild type.
• Sequencing revealed Tn5 insertion disrupted the purB gene, encoding adenylosuccinate lyase.
• The SRMT mutant produced significantly less exopolysaccharide and biofilm.

Conclusions:

• The purB gene is essential for rhizosphere competence and root colonization in Pantoea agglomerans.
• Disruption of purB impairs biofilm formation, impacting colonization ability.
• This research highlights the functional role of purB in rhizobacterial root colonization.