The extreme plant-growth-promoting properties of Pantoea phytobeneficialis MSR2 revealed by functional and genomic analysis.

Numerous Pantoea strains are important because of the benefit they provide in the facilitation of plant growth. However, Pantoea have a high level of genotypic diversity and not much is understood regarding their ability to function in a plant beneficial manner. In the work reported here, the plant growth promotion activities and the genomic properties of the unusual Pantoea phytobeneficialis MSR2 are elaborated, emphasizing the genetic mechanisms involved in plant colonization and growth promotion. Detailed analysis revealed that strain MSR2 belongs to a rare group of Pantoea strains possessing an astonishing number of plant growth promotion genes, including those involved in nitrogen fixation, phosphate solubilization, 1-aminocyclopropane-1-carboxylic acid deaminase activity, indoleacetic acid and cytokinin biosynthesis, and jasmonic acid metabolism. Moreover, the genome of this bacterium also contains genes involved in the metabolism of lignin and other plant cell wall compounds, quorum-sensing mechanisms, metabolism of plant root exudates, bacterial attachment to plant surfaces and resistance to plant defences. Importantly, the analysis revealed that most of these genes are present on accessory plasmids that are found within a small subset of Pantoea genomes, reinforcing the idea that Pantoea evolution is largely mediated by plasmids, providing new insights into the evolution of beneficial plant-associated Pantoea.

Plant growth-promoting activities and genomic analysis of the stress-resistant Bacillus megaterium STB1, a bacterium of agricultural and biotechnological interest.

In this work, the stress-resistant Bacillus megaterium STB1 is characterized and its ability to promote plant growth under normal and stress conditions is demonstrated. The genomic sequence of this bacterium, and a detailed analysis of the genes involved in facilitating its stress resistance and plant growth-promoting activities is also reported. The B. megaterium STB1 genome is rich in genetic elements involved in multiple stress resistance, xenobiotic degradation, pathogen antagonistic activities, and other traits related to soil and rhizosphere colonization. Moreover, genes participating in the biosynthesis of auxins and cytokinins, the modulation of polyamines, GABA, brassinosteroids and ethylene levels were also found. Ultimately, this study brings new insights into the role of B. megaterium as a plant growth-promoting bacterium and opens new opportunities for the development of novel strategies for agriculture and biotechnology.