Enhance of tomato production and induction of changes on the organic profile mediated by Rhizobium biofortification.

Introduction: The extensive use of chemical fertilizers has served as a response to the increasing need for crop production in recent decades. While it addresses the demand for food, it has resulted in a decline in crop productivity and a heightened negative environmental impact. In contrast, plant probiotic bacteria (PPB) offer a promising alternative to mitigate the negative consequences of chemical fertilizers. PPB can enhance nutrient availability, promote plant growth, and improve nutrient uptake efficiency, thereby reducing the reliance on chemical fertilizers. Methods: This study aimed to evaluate the impact of native Rhizobium strains, specifically Rhizobium calliandrae LBP2-1, Rhizobium mayense NSJP1-1, and Rhizobium jaguaris SJP1- 2, on the growth, quality, and rhizobacterial community of tomato crops. Various mechanisms promoting plant growth were investigated, including phosphate solubilization, siderophore production, indole acetic acid synthesis, and cellulose and cellulase production. Additionally, the study involved the assessment of biofilm formation and root colonization by GFP-tagged strains, conducted a microcosm experiment, and analyzed the microbial community using metagenomics of rhizospheric soil. Results: The results showed that the rhizobial strains LBP2-1, NSJP1-1 and SJP1-2 had the ability to solubilize dicalcium phosphate, produce siderophores, synthesize indole acetic acid, cellulose production, biofilm production, and root colonization. Inoculation of tomato plants with native Rhizobium strains influenced growth, fruit quality, and plant microbiome composition. Metagenomic analysis showed increased Proteobacteria abundance and altered alpha diversity indices, indicating changes in rhizospheric bacterial community. Discussion: Our findings demonstrate the potential that native Rhizobium strains have to be used as a plant probiotic in agricultural crops for the generation of safe food and high nutritional value.

Endofungal Rhizobium species enhance arsenic tolerance in colonized host plant under arsenic stress.

Arsenic (As) is a toxic metalloid that is present in natural surroundings in many forms with severe consequences to sustainable agriculture and human health. Plant growth-promoting Rhizobia have been found involved in the induction of plant tolerance under various biotic and abiotic stresses. An endofungal Rhizobium species associated with arbuscular mycorrhizal fungi (AMF) Serendipita indica deploy beneficial role in the promotion of plant growth and tolerance against various biotic and abiotic stresses. In the current study, we have determined the role of endofungal Rhizobium species in protection of host plant growth under As stress. We observed that endofungal Rhizobium species strain Si001 tolerate AsV up to 25 mM and its inoculation enhances tomato seed germination and seedling growth. A hyper-colonization of Rhizobium species Si001 in tomato roots was observed under As stress and results in modulation of GSH and proline content with reduced ROS. Rhizobium species Si001 colonization in host plant recovered pigment contents (chlorophyll-a and chlorophyll-b up to 189.5% and 192%, respectively), photosynthesis (157%), and water use efficiency (166%) compared to As-treated plants. Interestingly, bacterial colonization results in 40% increased As accumulation in the root, while a reduction in As translocation from root to shoot up to 89% was observed as compared to As treated plants. In conclusion, endofungal Rhizobium species Si001 association with the host plant may improve plant health and tolerance against As stress with reduced As accumulation in the crop produce.

Genomic comparisons of Rhizobium species using in silico AFLP-PCR, endonuclease restriction, and AMPylating enzymes

Background: The whole-genome sequences of nine Rhizobium species were evaluated using different in silico molecular techniques such as AFLP-PCR, restriction digest, and AMPylating enzymes. The entire genome sequences were aligned with progressiveMauve and visualized by reconstructing phylogenetic tree using NTSYS pc 2.11X. The "insilico.ehu.es" was used to carry out in silico AFLP-PCR and in silico restriction digest of the selected genomes. Post-translational modification (PTM) and AMPylating enzyme diversity between the proteome of Rhizobium species were determined by novPTMenzy. Results: Slight variations were observed in the phylogeny based on AFLP-PCR and PFGE and the tree based on whole genome. Results clearly demonstrated the presence of PTMs, i.e., AMPylation with the GS-ATasE (GlnE), Hydroxylation, Sulfation with their domain, and Deamidation with their specific domains (AMPylating enzymes) GS-ATasE (GlnE), Fic, and Doc (Phosphorylation); Asparagine_hydroxylase and Collagen_prolyl_lysyl_hydroxylase; Sulfotransferase; and CNF (Cytotoxic Necrotizing Factors), respectively. The results pertaining to PTMs are discussed with regard to functional diversities reported in these species. Conclusions: The phylogenetic tree based on AFLP-PCR was slightly different from restriction endonuclease- and PFGE-based trees. Different PTMs were observed in the Rhizobium species, and the most prevailing type of PTM was AMPylation with the domain GS-ATasE (GlnE). Another type of PTM was also observed, i.e., Hydroxylation and Sulfation, with the domains Asparagine_hydroxylase and Collagen_prolyl_lysyl_hydroxylase and Sulfotransferase, respectively. The deamidation type of PTM was present only in Rhizobium sp. NGR234. How to cite: Qureshi MA, Pervez MT, Babar ME, et al. Genomic comparisons of Rhizobium species using in silico AFLP-PCR, endonuclease restrictions and ampylating enzymes.

Structural and biochemical characterization of a carbohydrate acetylesterase from Sinorhizobium meliloti 1021.

In many microorganisms, carbohydrate acetylesterases remove the acetyl groups from various types of carbohydrates. Sm23 from Sinorhizobium meliloti is a putative member of carbohydrate esterase family 3 (CE3) in the CAZy classification system. Here, we determined the crystal structure of Sm23 at 1.75 Å resolution and investigated functional properties using biochemical methods. Furthermore, immobilized Sm23 exhibited improved stability compared with soluble Sm23, which can be used for the design of plant cell wall degrading-systems.

Biodegradation of Selected Nigerian Fruit Peels by the use of a Non-pathogenic Rhizobium species CWP G34B.

This study was carried out to determine the ability of Rhizobium species CWP G34B to degrade the peels of selected Nigerian fruits. The potential of the bacterium to digest some carbon sources (lactose, maltose, sucrose and mannitol) and peels of some Nigerian fruits (pineapple, orange, plantain, banana, pawpaw and mango fruits) was investigated by growing the organism on the substances separately after which DNSA reagent method was used to quantify glucose released into the medium. The results showed that the bacterium was able to degrade all the carbohydrates with the highest and the lowest glucose concentrations of 5.52 mg/ml for lactose and 0.50 mg/ml for mannitol. The carbohydrate-catabolic-enzyme (CCE) activity ranged from 0.169 mg/ml to 1.346 mg/ml glucose per mg/ml protein. Mannitol exhibited the highest CCE activity while the lowest activity was observed in the presence of sucrose. The amount of extracellular protein synthesized was highest (9.803 mg/ml) in the presence of maltose and lowest (0.925 mg/ml) in mannitol. The mean polygalacturonase activity was 0.54 unit/ml when the bacterium was grown in pectin in contrast to 0.28 unit/ml when it was grown in mannitol. The bacterium showed ability to breakdown the peels of the Nigerian fruits with the highest capability in banana and pineapple (0.42 and 0.41 mg/ml glucose per mg/ml protein respectively). The fruit-peel-degrading enzyme activity was lowest in orange peel (0.75 unit/ml).