Study of the physiological and biochemical characteristics of Cupriavidus metallidurans YX16 and growth-promoting on maize seedlings under salt stress.
Findings indicate that Cupriavidus metallidurans YX16 is a salt-tolerant plant growth-promoting rhizobacterium (PGPR) that effectively alleviates salt-induced damage and promotes maize growth, providing a basis for the development of microbial agents for the amelioration of saline-alkali soils.
Abstract
Background
Driven by the dual pressures of continuous global population growth and dwindling arable land, ensuring food security has become a paramount challenge for human society. However, soil salinization, a primary abiotic stress factor limiting agricultural production, is degrading vast tracts of arable land globally and causing drastic reductions in crop yields. Consequently, harnessing microorganisms to enhance crop adaptability to saline-alkaline environments has become a critical focus in the reclamation and utilization of these degraded soils.
Results
In this study, a salt-tolerant plant growth-promoting bacterium, Cupriavidus metallidurans strain YX16, was isolated from the red soil of Yunnan Province in China. It is characterized by salt tolerance, nitrogen fixation, inorganic phosphorus solubilization, and indole-3-acetic acid (IAA) production (83.75 ± 1.14 µg/mL), but lacks the ability to solubilize potassium and organic phosphorus, and it does not produce siderophores or 1-aminocyclopropane-1-carboxylate (ACC) deaminase. Under salt stress, compared to the control group, the YX16 suspension treatment elevated the primary root length, plant height, root dry weight, shoot fresh weight, and shoot dry weight by 23.95%, 52.45%, 28.38%, 51.46%, and 107.69%, respectively. Furthermore, the total root length and root surface area increased by 44.08% and 32.48%, respectively. Inoculation with the YX16 suspension also promoted the accumulation of osmotic regulatory substances in maize, thereby activating the antioxidant system and reducing the malondialdehyde (MDA) content in roots and leaves by 27.50% and 49.57%, respectively. Under non-salt stress conditions, compared with the uninoculated control, the YX16 treatment decreased the root soluble sugar content by 20.64% and the leaf CAT activity by 13.08%, but elevated the root proline content by 29.16%, the root dry weight by 18.75%, and the leaf chlorophyll content by 12.74%; however, other antioxidant enzyme (SOD, POD) activities and root dehydrogenase activity (DHA) were not significantly affected.
Conclusions
These findings indicate that Cupriavidus metallidurans YX16 is a salt-tolerant plant growth-promoting rhizobacterium (PGPR) that effectively alleviates salt-induced damage and promotes maize growth, providing a basis for the development of microbial agents for the amelioration of saline-alkali soils.
Soil salinization and phosphorus (P) deficiency are critical environmental challenges that severely limit global ag - ricultural productivity, particularly in the arid regions of Uzbekistan. Under saline conditions, P is rapidly immobilized, becoming unavailable for plant uptake, which leads to stunted growth and significant yield losses. This study addresses the urgent need for sustainable bio-remediation by evaluating halotolerant endophytic bacteria as effec - tive bio-fertilizers. Several endophytic bacterial strains isolated from native halophytes were screened for their tolerance to extreme salinity (up to 10% NaCl) and their ability to solubilize insoluble phosphates. The most potent isolates, Pseudomonas putida KoPr129 and Bacillus amyloliquefaciens HAPH2, were biochemically characterized for plant growth-promoting (PGP) traits, including IAA, ammonia, and HCN production. A 6-week greenhouse pot experiment was conducted to validate their efficacy on wheat ( Triticum aestivum L.) under 150 mM NaCl stress and P-deficient conditions. In vitro assays confirmed that P. putida KoPr129 maintained a robust phosphate solu - bilization index (FPI 18.16±0.56 mm) even at 10% NaCl. Greenhouse trials demonstrated that inoculation with these endophytes significantly mitigated the negative impacts of combined stress. Specifically, P. putida KoPr129 increased wheat shoot length by 9% and more than doubled the total phosphorus uptake (over 130% increase) compared to the non-inoculated stressed control. Biochemical profiling revealed high levels of IAA produc - tion in both strains, facilitating enhanced root architecture and nutrient acquisition. Our findings demonstrate that halotolerant endophytes, particularly P. putida KoPr129, are superior candidates for the development of effective bio-inoculants. These results provide a promising pathway to restore soil fertility and improve wheat productivity in degraded, saline-alkali landscapes, offering a sustainable alternative to chemical fertilizers.
Shahzod Axanbayev, Zafar Rakhmonov, M. Norboyev et al.· Journal of Ecological Engine...· 0 citations
The growing global population and rising food demand have intensified reliance on chemical fertilizers, leading to soil degradation, environmental pollution, and heavy metal accumulation. As a sustainable alternative, Trichoderma spp. have gained prominence as bioinoculants due to their diverse plant growth-promoting abilities. However, emerging evidence highlights strain-specific variability and regulatory complexity in their beneficial traits, aspects that remain insufficiently addressed in current literature. This review explores the molecular basis of three key mechanisms: (i) indole-3-acetic acid (IAA) biosynthesis through indole-3-pyruvic acid (IPA), indole-3-acetamide (IAM), and tryptophan-independent pathways; (ii) phosphate solubilization mediated by phytase, phosphatase, and organic acid production; and (iii) iron (Fe) acquisition through siderophore production, primarily synthesized by nonribosomal peptide synthetases (NRPSs). Not all Trichoderma species exhibit the full spectrum of plant growth-promoting traits; while some are efficient in phosphate solubilization, others may primarily contribute through IAA production or siderophore production. Genomic and bioinformatic studies have revealed that T. atroviride, T. asperellum, T. virens, T. harzianum, T. citrinoviride, T. reesei, T. longibrachiatum, and T. koningiopsis harbor putative genes encoding proteins homologous to enzymes associated with IAA production, such as flavin monooxygenase and indoleamine-2,3-dioxygenase, as well as genes involved in siderophore production, including sidA, sidF, sidL, sidC, sidD, and sidG. However, the genetic and regulatory mechanisms underlying IAA production and phosphate solubilization in Trichoderma remain poorly characterized, with limited genomic information available on genes encoding auxin-related enzymes, phytases, acid phosphatases, and those involved in organic acid biosynthesis. These findings highlight the importance of targeted molecular research to support the development of strain-specific bioformulations that enhance nutrient use efficiency, reduce chemical inputs, and advance sustainable agricultural practices.
Jerry Junior Rama, D. David, Ahmad Asnawi Bin Mus et al.· Recent Advances in Food Nutr...· 0 citations
Drought stress is among the most critical limitations to maize productivity, particularly under rainfed conditions. In this study, we explored the Brazilian Caatinga biome as a source of drought adapted plant growth-promoting bacteria and evaluated their potential to mitigate drought effects in maize (Zea mays L.). A total of 414 thermo-tolerant bacterial strains were isolated from soil, of which 28 Bacillus strains were able to grow under low water activity. These strains exhibited multiple plant growth-promoting traits in vitro, including exopolysaccharide production, biofilm formation, siderophore production, indole-3-acetic acid synthesis, putative nitrogen fixation, and phosphate solubilization. Twelve selected strains significantly improved root morphology, relative chlorophyll content (SPAD units), and biomass accumulation in maize seedlings under osmotic stress induced by polyethylene glycol. Notably, strain 1A11 showed the most consistent effects, promoting root growth and biomass accumulation under both stressed and non-stressed conditions, indicating constitutive growth promotion across environments, whereas other strains showed stronger responses under stress. This stability across environments strengthens its agronomic value, particularly in regions characterized by high rainfall variability. Genome sequencing of five elite strains (1A11, 5D5, 6E9, 1H10, and 2E7) identified conserved gene clusters associated with exopolysaccharide production, indole-3-acetic acid synthesis, phosphate metabolism, iron acquisition (siderophore synthesis), synthesis of volatile compounds, motility, chemotaxis, and general responses to osmotic and oxidative stress. Multi-location field trials conducted across five locations in Brazil, under rainfed conditions, indicate that strains 1A11 (Bacillus subtilis), 5D5, and 6E9 (Bacillus velezensis) consistently increased grain yield compared to the non-inoculated control and performed similarly to or better than a commercial inoculant. Mean productivity gains with the strain 1A11 reached up to 39% relative to the non-inoculated treatment across environments. These results indicate that Bacillus strains isolated from semi-arid soils were able to convert multifunctional potential into measurable agronomic gains under field conditions, demonstrating their potential as bioinoculants to enhance maize resilience under water-limited agricultural systems.
U. G. Lana, S. M. de Sousa, Bárbara Temponi Vilarino Godinho et al.· Frontiers in Plant Science· 0 citations
The combined application of microbial inoculation and seedling transplanting is recommended for large-scale and high-quality cultivation of G. uralensis in moderately saline-alkali soils of arid northwestern China, as this integrated practice maximizes plant growth, medicinal compound accumulation, and rhizosphere microenvironment optimization.
Qihao Guo, Jun Zhang, Xin Li et al.· Environmental Microbiome· 0 citations
Enhanced soil salinity is a major constraint to rice production in the coastal regions of Bangladesh. Salinity stress impairs nutrient uptake and induces ionic toxicity and osmotic stress, while excessive use of chemical fertilizers degrades soil health and causes environmental pollution. A novel salt-tolerant endophytic fungus, Aspergillus welwitschiae Ocstreb1, isolated from the halophytic wild rice Oryza coarctata, exhibited multiple plant growth–promoting traits under both non-saline and 900 mM salt-stress conditions in vitro. These findings suggest that Ocstreb1-based biofertilizer could serve as an eco-friendly and cost-effective alternative to enhance rice productivity under saline conditions. In this experiment, the biofertilizer was prepared using fungal spores produced on wheat bran and subsequently mixed with talcum powder as a carrier. Field trials were conducted following a randomized complete block design (RCBD), incorporating different levels of chemical fertilizer application (0%, 80%, and 100% of the BRRI-recommended NPKSZn rates) in both biofertilizer-treated and untreated plants. Compared with the 100% chemical fertilizer treatment, the combined application of biofertilizer and 80% chemical fertilizer resulted in a comparable yield in Barguna and increased yield of 196.6 kg ha⁻¹ in Satkhira. Profitability analysis showed that this treatment provided an additional economic benefit of USD 48–68 ha⁻¹ over the 100% chemical fertilizer treatment. Moreover, fumonisin B1 levels in grains from biofertilizer-treated plants were negligible. In conclusion, commercial production of this biofertilizer will pave the way for enhancing rice yield with less use of chemical fertilizer while promoting sustainable agricultural practice particularly in areas affected by salinity stress.
Amit Chowdhury, J. Bhattacharya, Md. Iyasir Arafat et al.· Discover Agriculture· 0 citations
This study introduces L. aquatilis strain MC3 as an emerging candidate for bioinoculant development and one of the first reports for identification of L. aquatilis as multifunctional PGPR from Himalayan ecosystems.
S. Devi, Riya Chandel, D. Thakur et al.· Frontiers in Systems Biology· 0 citations