Role of Bacillus subtilis exopolymeric genes in modulating rhizosphere microbiome assembly.

BACKGROUND: Bacillus subtilis is well known for promoting plant growth and reducing abiotic and biotic stresses. Mutant gene-defective models can be created to understand important traits associated with rhizosphere fitness. This study aimed to analyze the role of exopolymeric genes in modulating tomato rhizosphere microbiome assembly under a gradient of soil microbiome diversities using the B. subtilis wild-type strain UD1022 and its corresponding mutant strain UD1022eps-TasA, which is defective in exopolysaccharide (EPS) and TasA protein production. RESULTS: qPCR revealed that the B. subtilis UD1022eps-TasA- strain has a diminished capacity to colonize tomato roots in soils with diluted microbial diversity. The analysis of bacterial ß-diversity revealed significant differences in bacterial and fungal community structures following inoculation with either the wild-type or mutant B. subtilis strains. The Verrucomicrobiota, Patescibacteria, and Nitrospirota phyla were more enriched with the wild-type strain inoculation than with the mutant inoculation. Co-occurrence analysis revealed that when the mutant was inoculated in tomato, the rhizosphere microbial community exhibited a lower level of modularity, fewer nodes, and fewer communities compared to communities inoculated with wild-type B. subtilis. CONCLUSION: This study advances our understanding of the EPS and TasA genes, which are not only important for root colonization but also play a significant role in shaping rhizosphere microbiome assembly. Future research should concentrate on specific microbiome genetic traits and their implications for rhizosphere colonization, coupled with rhizosphere microbiome modulation. These efforts will be crucial for optimizing PGPR-based approaches in agriculture.

Draft genome sequences of Streptomyces virginiae strain CMAA1738, Paenibacillus ottowii strain CMAA1739 and Pseudomonas inefficax strain CMAA1741, isolated from rhizosphere of wheat landraces.

In this study, we have identified and characterized three genomes from bacteria isolated from the rhizosphere of Triticum aestivum. Streptomyces virginiae CMAA1738 and Paenibacillus ottowii CMAA1739 were obtained from the wheat landrace Iran 1-29-11334, and Pseudomonas inefficax CMAA1741 was isolated from the wheat landrace Karakilcik.