Plant growth-promoting yeasts are promising bioinoculants for low-input agriculture, yet their application remains underexplored. We isolated 25 epiphytic strains from Vitis vinifera subsp. sylvestris and performed systematic in vitro biochemical profiling of plant growth promoting (PGP) traits. All produced indole-3-acetic acid (IAA); 80% synthesized under L-tryptophan-free conditions, indicating tryptophan-independent routes. ACC deaminase, siderophores, ammonia release, catalase, and biofilm were widespread, whereas nutrient solubilization (P, K, Zn), polyamines, and hydrolases (proteases, chitinases, β-1,3-glucanases, lipases, esterases) were strain-dependent, guiding evidence-based selection. Twelve representatives were evaluated in greenhouse with Nicotiana tabacum; ten increased biomass, leaf area, and root traits versus the control. The standout strains were Wickerhamomyces anomalus C(H5.1), Metschnikowia pulcherrima B(B5) and C(A11.2), Pichia kudriavzevii C(A7), and Yarrowia lipolytica B(H3.1.1), each displaying broad functional repertoires and consistent greenhouse performance. Growth promotion occurred without detectable shifts in bulk soil chemistry, supporting native epiphytic yeasts as multifunctional, soil safe bioinoculant candidates.

Cadmium (Cd)-tolerant plant growth-promoting rhizobacteria have garnered significant attention in Cd2+ remediation owing to their dual capabilities of mitigating heavy metal stress and enhancing plant growth. A rhizobacterial strain exhibiting elevated 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production was isolated from Cd-contaminated soil and genotypically characterized as Ensifer morelensis A23T. This work establishes the first documented evidence of significantly enhanced ACC deaminase activity in Ensifer morelensis under 50 mg L-1 Cd2+ exposure. Genomic analysis identified multiple functional genes implicated in Cd2+ tolerance and plant growth promotion. Transcriptome profiling revealed that Cd2+ stress significantly induced the expression of ACC deaminase-associated genes while concurrently downregulating cell cycle-related genes, suggesting a potential adaptive response to Cd-induced cytotoxicity. Furthermore, inoculation with strain A23T significantly enhanced rapeseed germination and seedling growth under Cd2+ stress. These findings underscore the potential utilization of strain A23T as a sustainable biological agent to support plant growth in cadmium-affected soils and provide novel insights into its molecular adaptation strategies to heavy metal stress.

Drought is a prolonged period of insufficient rainfall, leading to water scarcity that adversely affects both the natural environment and human endeavours. Water scarcity disrupts photosynthesis, resulting in underdeveloped, smaller plants, wilting leaves, reduced root growth, and, under severe conditions, plant death. Drought remains one of the most significant challenges to global food security, causing crop failures, rising food prices, and widespread malnutrition. The key objective of the present investigation was to isolate bacterial species capable of surviving drought conditions and to evaluate their plant growth-promoting potential. The Bacillus cereus DS1 strain was isolated from a soil sample collected from the rhizospheric region of the drought-tolerant plant Celosia argentea. Among the various tested osmotic pressure conditions, Bacillus cereus DS1 not only significantly tolerated 5% PEG 8000 (−0.47 MPa osmotic pressure) but also exhibited promising plant growth-promoting properties. The in vitro plant growth-promoting activity of the isolate was evaluated using various tests, including hydrogen cyanide, indole acetic acid, ammonia, and siderophore production; ACC deaminase activity; and phosphate solubilization and nitrogen fixation under both stress and non-stress conditions. Additionally, the effect of Bacillus cereus DS1 on seed germination was assessed, and a notable enhancement of 88% seed germination was observed in bioprimed seeds compared to the control (seeds primed with distilled water). Overall, the local isolate Bacillus cereus DS1 has the potential to withstand various levels of drought stress and enhance seed germination under drought conditions, indicating that it could serve as a valuable bioinoculant for improving crop yield in arid and semi-arid regions.

Moisture stress is one of the major factors affecting crop productivity and food security. Although several management practices are available, eco-friendly microbial approaches provide sustainable solutions through mechanisms such as nutrient solubilization, phytohormone production, biofilm formation, osmolyte accumulation and metabolite production. Among plant growth-promoting microbes, yeasts remain less explored for their role in drought tolerance. The present study aimed to evaluate the potential of yeast in mitigating moisture stress and promoting rice growth. Fifty isolates were obtained from soil samples, of which 18 isolates survived up to 30% PEG 6000. Further, the isolates were evaluated for plant growth-promoting (PGP) traits, including the indole acetic acid, siderophore, and exopolysaccharides production, phosphorus and zinc solubilization, and biofilm formation under increasing PEG concentrations (0, 10, 20 and 30%). Among the 18, five well-performing isolates S2R2, CAL, SF, SA1, and V1BG were selected for further experiments. All these five isolates demonstrated ACC deaminase activity (maximum of 111.50 nmole of α-ketobutyrate mg- 1 protein h- 1) and osmolytes accumulation such as proline, trehalose and glycine betaine. Moreover, these isolates on seed biotization improved seed germination and seedling growth under moisture stress. Metabolite profiling revealed that production of phenols, alkaloids, and amino acids was predominant under PEG-induced stress and associated with plant growth promotion. Overall findings highlight the potential of yeast as bioinoculants for enhancing drought resilience and growth promotion in rice.

Here, ACC deaminase ACC Deaminase producing rhizobacteria, Priestia aryabhattai MD-85 (Accession no. PV155249.1) and Enterobacter cloacae MD-79 (Accession no. PV155250.1), were assessed for their potential to enhance water-deficit stress tolerance in muskmelon. Both strains produced ACC Deaminase and exhibited drought tolerance, with MD-79 showing 78.9 ± 7.6 µM α-ketobutyrate mg⁻¹ protein h⁻¹ at 18%-PEG, and MD-85 showing 68.4 ± 5.4 µM α-ketobutyrate mg⁻¹ protein h⁻¹ at 21%-PEG. Both strains produced multi-functional growth-promoting substances under PEG-induced stress, conferring their significant drought tolerance potential. Increasing water stress negatively impacted growth and physiological characteristics of soil-grown muskmelon plants. However, ACC Deaminase-producing strains, especially when applied in combination (P. aryabhattai MD-85 + E. cloacae MD-79), effectively mitigated adverse effects of drought stress. For instance, under 3%-polyethylene glycol (PEG)-induced stress in muskmelon, co-inoculation (MD-79 + MD-85) enhanced root length (44.3%), shoot length (47.6%), root dry and fresh wight ratio (40.7%), leaf dry and fresh wight ratios (51.7%), total chlorophyll (41.5%), and carotenoids (38.8%). Further, bacterial consortia significantly (p ≤ 0.05) enhanced chlorophyll colour index (56.7%), net photosynthetic rate (64.3%), Fv/Fm (50.8%), stomatal conductance (64.3%) and relative water content (62.3%) in leaf tissues of 3%-PEG-stressed muskmelon. Single/combined bacterial inoculation lowered drought-induced oxidative stress markers in muskmelon. Moreover, bacterial partners strengthened antioxidant enzymes in water-deficit affected muskmelon. The 15%-PEG + MD-79 + MD-85 treatment exhibited greater increase in catalase (79.3%), ascorbate peroxidase (65.3%), peroxidase (55.7%), and superoxide dismutase (72%), activities over their respective untreated controls. Additionally, bacterial strains modulated ion homeostasis in PEG-stressed muskmelon roots, enhancing drought tolerance. Notably, combined inoculation synergistically enhanced drought tolerance compared to single-strain treatments. This study emphasizes the potential of ACC Deaminase-producing PGPR as a sustainable and long-term strategy to improve muskmelon resilience under water-deficit condition by modulating physiological, biochemical, and ionic responses. These findings underscore the use of PGPR in drought management to enhance crop productivity and stress tolerance.

The dual role of ethylene in plant growth and abiotic stress: Mechanisms, regulation, and mitigation through ACC deaminase.

Pantoea is a genus of Gram-negative bacteria isolated from diverse environments. Over time, it has drawn considerable attention for its potential to promote plant growth. However, its biotechnological application is complicated by high genomic plasticity, which underlies both its beneficial traits and its ability to cause disease in a wide range of plants, as well as occasional opportunistic infections in humans, raising biosafety concerns. In this study, we conducted a comparative genomic analysis of all publicly available Pantoea genomes. Our goals were to refine taxonomic classifications and to identify genes linked to biotechnological potential, virulence, and antibiotic resistance, thereby clarifying lifestyle strategies within the genus. We found that plant growth-promoting genes are widely conserved, particularly those involved in phosphate solubilization, phytohormone biosynthesis, and siderophore production. In contrast, traits such as nitrogen fixation and ACC deaminase activity were restricted to specific species. The resistome analysis revealed intrinsic resistance mechanisms conserved across the genus, primarily involving diverse efflux pump families and β-lactamases conferring resistance to cephalosporins. In parallel, the pan-GWAS highlighted lifestyle-defining genetic markers, including the hrp/hrc genes encoding type III secretion system components, pepM (phosphoenolpyruvate mutase) associated with the production of a phytotoxin, and ibeB, an invasin linked to clinical infections. Together, our findings underscore both the biotechnological potential of Pantoea and the importance of genetic markers for distinguishing beneficial from pathogenic lifestyles, supporting the safe application of selected strains in biotechnology.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11274-025-04780-2.

Endophytic bacteria are key mediators of plant growth promotion and pesticide detoxification, yet the genomic mechanisms enabling these dual functions remain underexplored. This study is aimed at exploring new endophytic strains from rice plants from pesticides contaminated soil with their genomic insights. Here, we report the whole-genome sequencing and in-silico functional characterization of Serratia sp. HSTU-ABk35, an endophyte isolated from rice plants (Oryza sativa). Genome analysis revealed a 5.18 Mb chromosome with a GC content characteristic of Serratia, harboring coding sequences associated with phytohormone biosynthesis, ACC deaminase activity, siderophore production, phosphate solubilization, oxidative stress tolerance, and systemic resistance induction. Phylogenomic analyses based on ANI, dDDH, and housekeeping genes (recA, gyrB, rpoB, and 16S rRNA) indicate that Serratia sp. HSTU-ABk35 closely related to Serratia marcescens but exhibits notable evolutionary divergence, suggesting novel genomic features potentially associated with its endophytic lifestyle and agrochemical adaptability. Functional annotation identified an array of xenobiotic-degrading genes, including esterases, amidohydrolases, α/β-hydrolases, and phosphonate-metabolizing operons, implicating the strain in the degradation of organophosphate, pyrethroid, and carbamate pesticides. Virtual screening and molecular docking of key pesticide-degrading proteins confirmed strong binding affinity and plausible enzyme–pesticide interactions, supporting the predicted biotransformation potential. Collectively, the genomic novelty and functional versatility of Serratia sp. HSTU-ABk35 highlight its promise as a multifunctional endophyte with potential applications in sustainable agriculture, including crop growth promotion, stress tolerance enhancement, and bioremediation of pesticide-contaminated soils.

ABSTRACTPlant growth‐promoting rhizobacteria (PGPR) that can break down 1‐aminocyclopropane‐1‐carboxylate (ACC), an ethylene precursor, by ACC deaminase enzymes (ACCd) to reduce ethylene production in plants may enhance plant tolerance to drought stress. This study aimed to identify genes in plant roots regulated by ACCd‐bacteria under drought stress and re‐watering and to determine major molecular factors and associated metabolic pathways for ACCd bacteria‐enhanced drought tolerance and post‐stress recovery in creeping bentgrass (Agrostis stolonifera). Transcriptomic analysis was performed in root tissues from plants inoculated with a novel strain of ACCd‐producing bacteria, Paraburkholderia aspalathi “WSF23,” under well‐watered conditions, 35 days of drought stress, and 15 days of re‐watering. ACCd bacteria inoculation resulted in differential expression of 53 genes under drought stress. Genes up‐regulated in inoculated roots during drought stress included SUMO (small ubiquitin‐like modifier) protease OTS1, an alcohol dehydrogenase (ADH2), desiccation‐related protein (DRP) gene pcC‐13362, cell wall structure and elasticity (TBL27), and antioxidant metabolism (DJ‐1C and 1CYSPRXA). For post‐drought recovery, inoculated plants differentially expressed 160 genes, including up‐regulation of DNA repair (RAD6), signal transduction (WRKY72), root growth and development (D10, WRKY74, ERF3), nitrogen transport (DUR3), and osmoregulation (CIPK23), as well as up‐regulation of carotenoid biosynthesis pathways. These findings help to explain the molecular mechanisms associated with ACCd bacteria‐mediated drought stress tolerance and post‐drought recovery in cool‐season perennial grass species, contributing to sustainable methods of reducing water use in turfgrass management.

The present study reports the isolation and identification of a γ-proteobacterium which is capable of degrading maneb and its photolytic product ethylene thiourea. The strain SDS18 was isolated from the surface of the most common weed Parthenium hysterophorus growing in agricultural field. Based on molecular systematics the strain SDS18 was identified as Pseudomonas psychrotolerans. Our study first time revealed that a single bacterial strain is capable of metabolising the toxic fungicide maneb and its carcinogenic photolytic product ethylenethiourea. We found that the strain SDS18 can tolerate upto 150ppm of maneb and 200 ppm of ethylene thiourea and ethylene urea as sole carbon sources. The optimum conditions for degradation were in the presence of ammonium sulphate as nitrogen source at 30°C at pH 7.0. Interestingly, the strain SDS18 exhibited activities like phosphate solubilisation, production and assimilation of ammonia, ACC deaminase activity, production of indole acetic acid and siderophores which are plant growth promoting activities and antifungal activities for Alternaria citri and Cladosporium cladosporioides indicating it could be beneficial for plant growth and maturation. The isolated strain can be used for bioremediation of maneb and its photolytic products.

BackgroundSoils suppressive to fungal pathogens harbor microbiomes that can inhibit disease development despite the presence of virulent pathogens and susceptible hosts. Fluorescent Pseudomonas are often implicated in such suppressiveness, but their genomic determinants and distribution in suppressive vs. non-suppressive (i.e., conducive) soils remain unclear.ResultsWe investigated the taxonomic and functional diversity of Pseudomonas populations from wheat rhizospheres in four agricultural soils with contrasting suppressiveness to Fusarium graminearum-induced seedling disease. rpoD-based metabarcoding and culture-dependent isolation revealed distinct Pseudomonas community structures linked to soil suppressiveness. However, major phylogenetic groups were shared across soils. From 406 isolates, 29 representative strains spanning seven subgroups of the P. fluorescens group were selected for whole-genome sequencing. Comparative genomics revealed 14 putative novel Pseudomonas genomospecies (dDDH < 70% with closest described type strains). Genomic screening revealed wide distribution of genes linked to biocontrol and plant-growth promotion, including siderophore biosynthesis, hormone modulation, phosphate solubilization, and production of antimicrobial compounds. Biosynthetic genes for phenazine and pyrrolnitrin were detected exclusively in P. chlororaphis strains isolated from suppressive soils, and rpoD alleles corresponding to these strains were not found in conducive soils within our metabarcoding dataset. Other traits such as hydrogen cyanide, ACC deaminase, and auxin biosynthesis were broadly distributed across isolates from all soils. Functional assays demonstrated variable expression of predicted traits, indicating regulatory or environmental influence. Several strains inhibited F. graminearum mycelial growth via volatile organic compounds, while two strains also reduced conidia germination, including isolates from both suppressive and conducive soils.ConclusionsThis study demonstrates that Pseudomonas genomic traits important for biocontrol are not restricted to suppressive soils, and that functional redundancy and context-dependent expression may shape the contribution of Pseudomonas to disease suppression. Our results highlight the need for integrative analyses combining community profiling, genome-based prediction, and phenotyping to better understand microbiome-mediated plant protection. The identification of novel genomospecies and lineage-specific biosynthetic traits advances our knowledge of Pseudomonas diversity in agricultural soils and supports future development of targeted microbial consortia.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12864-025-12374-3.

Ensuring sufficient crop yields in an era of rapid population growth and limited arable land requires innovative strategies to enhance plant resilience and sustain, or even improve, growth and productivity despite environmental stress. Besides symbiotic nitrogen fixation, rhizobia may play a central role in sustainable agriculture by alleviating the detrimental effects of ethylene-a key stress hormone in plants-especially under conditions like drought through the deamination of 1-aminocyclopropane-1-carboxylic acid (ACC). In this study, we focused on genetically engineering a new Bradyrhizobium sp. isolate (Strain 9) from peanut root nodules to enhance its ACC deaminase activity. First, we developed a sacB-based genome-engineering tool and used it to knock out the ACC deaminase gene (acdS), confirming that its disruption severely diminished the strain's capacity to degrade ACC. Subsequently, we constructed an acdS-overexpressing strain by integrating a strong promoter and an optimized ribosome binding site upstream of acdS, achieving a five-fold increase in ACC deaminase activity relative to the wild-type. Peanut inoculation experiments demonstrated that both the acdS knockout and overexpression mutants effectively nodulated roots without impairing plant growth and nitrogen fixation, indicating that these modifications did not compromise symbiosis. Overall, this study highlights the utility of sacB-mediated counter-selection for precise genome editing in Bradyrhizobium and underscores the potential of enhanced ACC deaminase activity to improve plant growth under stress conditions. These findings pave the way for developing next-generation bioinoculants with superior ethylene mitigation capabilities, contributing to more productive and sustainable crop systems.

Biopriming with halotolerant microbes enhances growth performance, resilience and rhizospheric microbial diversity of Solanum melongena under saline conditions.

Endophytes-mediated mitigation of sodium stress in plants via ABA-independent signaling pathways.

Lead (Pb) contamination poses a serious threat to soil ecosystems, crop productivity, and food safety. The use of Pb-resistant plant growth-promoting bacteria (PGPB) offers a sustainable and eco-friendly strategy for soil bioremediation. In this study, a novel Pb-tolerant PGPB strain, Pseudomonas mendocina L1, was isolated from phosphate rock-contaminated soil. Strain L1 exhibited high Pb resistance (MIC = 1000mg/L) and multiple plant growth-promoting traits, including phosphate solubilization, indole-3-acetic acid (IAA) and siderophore production, as well as ACC deaminase activity. Whole-genome sequencing (WGS) revealed that strain P. mendocina L1 harbors a 5.54Mb circular chromosome with a GC content of 62.39% and 5136 predicted coding sequences. Genomic analysis identified key genes involved in plant-beneficial functions, such as phosphate transport (pstA, pstB, pstC, pstS), siderophore-mediated iron uptake (fhuB, fhuC, fhuD), and IAA biosynthesis (trpEDCBA operon, trpF). Furthermore, a soil-pakchoi (Brassica chinensis L.) system was employed to evaluate its bioremediation potential, demonstrating that inoculation with P. mendocina L1 significantly improved plant growth while reducing Pb accumulation in edible tissues. These findings highlight P. mendocina L1 as a promising candidate for the bioremediation of Pb-contaminated soils, offering an eco-friendly and cost-effective strategy for sustainable agriculture and environmental restoration.

BackgroundPseudomonas argentinensis SA190 is a desert-adapted, plant-associated bacterium with demonstrated potential to enhance plant growth under abiotic stress. In this study, we conducted a comprehensive genomic and functional characterization of SA190 to uncover the molecular mechanisms underlying its biofilm formation, root colonization, and plant growth-promoting traits.ResultsThe SA190 genome consists of a single circular chromosome (5.07 Mb, 64% GC) encoding 4561 predicted ORFs. Functional annotation revealed genes related to phosphate solubilization (pqq operon), antifungal activity, and stress mitigation, including ACC deaminase. AntiSMASH analysis identified eight biosynthetic gene clusters linked to secondary metabolite production, including siderophores, terpenes, and β-lactones. Metabolic profiling demonstrated selective utilization of root exudate-associated sugars, consistent with rhizosphere adaptation. By a Tn5 transposon mutagenesis approach, we identified key regulators required for biofilm formation. Biofilm mutants deficient in wspC, rpoE, and fliD were differentially compromised in plant colonization and plant growth promotion under ambient and/or drought conditions.ConclusionOur study suggests that SA190 is a metabolically streamlined yet ecologically versatile PGPB and provides functional insights into its potential application as a bioinoculant for sustainable agriculture in arid environments.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12866-025-04495-2.

Plant growth-promoting rhizobacteria (PGPR) are essential for increasing crop resistance to abiotic stressors, especially salinity. The halotolerant rhizospheric strain Staphylococcus epidermidis DS2, isolated from cotton rhizosphere, was tested for its ability to promote salt tolerance in two wheat cultivars (Wadan and Pirsabak2019). The strain exhibited a variety of plant growth promoting (PGP) properties in saline conditions, such as exopolysaccharides (3.33mgmL⁻1), indole-3-acetic acid (128µMmL⁻1), and ACC deaminase activity (1.92µMmg⁻1 protein h⁻1). In both cultivars, DS2 inoculation markedly increased fresh and dry biomass, as well as shoot and root length, in non-saline circumstances. Under moderatesalt stress (100mM NaCl), DS2-treated plants exhibited elevated levels of chlorophyll a and total chlorophyll (up to 37% in Wadan), as well as improved relative water content. In conditions of significant stress (150mM NaCl), inoculated plants preserved elevated chlorophyll concentrations and exhibited diminished oxidative damage, as seen by reduced levels of malondialdehyde (48%) and hydrogen peroxide (23%). Activities of antioxidant enzymes, such as peroxidase (168%) and catalase (45%), were increased. The DS2 inoculation diminished Na⁺ buildup while enhancing the absorption of K⁺, Mg2⁺, and Ca2⁺, hence facilitating improved ionic equilibrium and stress alleviation. The results indicate that S. epidermidis DS2 has potential as a bioinoculant to improve wheat performance in saline environments.

The use of beneficial bacterial strains is proposed as a nature based practice to support sustainable crop production. Strains exposed to extreme environmental stress may have developed robust stress resistance and the capacity to enhance plant growth under unfavorable conditions. Our study provides the new aspect in characterising bacteria from polluted soil. The novelty of our study was isolation of bacteria from a long-term contaminated site and their testing for plant growth promoting mechanisms. The aim of this research was to characterize bacterial strains, collected from the root zone of grasses growing in a heavily polluted smelter wasteland reclaimed 25 years ago using sewage sludge and by-product lime. Their capability to enhance plant resistance to stresses has not been widely assessed. The activity of the strains was assessed based on mechanisms associated with nutrient uptake: phosphate solubilization, ability to fix atmospheric nitrogen (N), ability to synthesize indole-3-acetic acid (IAA)-like compounds, and mechanisms linked to plant stress tolerance: ACC deaminase production, polysaccharides and biofilm development. Metabolic profiling of the strains was performed. Most strains tested in this study exhibited a range of plant growth promotion mechanisms. All strains solubilized phosphates with medium to high intensity, 14 of 15 isolates produced IAA up to 60 µg/mL, all fixed N from 15.85 to 50.00 mg/ml after 72 h. Thirteen strains survived freeze-drying. Our study enabled clustering bacterial strains with capability to perform certain groups of processes. Strains intensively fixing N in general were also able to intensively produce IAA but rather were not efficient producers of extracellular polymeric substances (EPS). IAA production was negatively correlated with 1-aminocyclopropane-1-carboxylic acid deaminase (ACC) deaminase activity and average carbon utilization intensity. All three strains selected for the pot study (Burkholderia sp., Pseudomonas caspiana, and Phyllobacterium sp.) confirmed the effectiveness in promoting wheat growth both at optimal and low soil moisture. The study shows that 25-years reclaimed smelter wastelands are reservoirs of PGPR strains potentially useful for developing biofertilizers enhancing plant growth and resistance to environmental or climatic stresses in agriculture.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-21980-w.

Vibrio is an important marine heterotroph, primarily studied for its pathogenesis or symbiotic relationship with marine organisms and humans. However, little is known about the association of vibrios with plants in brackish environments and their potential benefits. To address this knowledge gap, we focused on Vibrio porteresiae MSSRF30T and brackish-grown Pokkali rice as our research subjects for this study. MSSRF30T displays multifaceted plant beneficial traits, including nitrogen fixation, 1-aminocyclopropane-1-carboxylate (ACC) deaminase production, and zinc and tricalcium phosphate solubilization. Further, MSSRF30T efficiently colonizes the host roots and significantly improves the Pokkali rice growth in nitrogen-replete and nitrogen-limiting brackish conditions, highlighting its plant growth-promoting ability, a trait previously not well recognized in vibrios. Additionally, MSSRF30T can utilize various carbon-rich substrates derived from plant roots, demonstrating its metabolic adaptation to the plant rhizosphere niche. Using in planta root transcriptome analysis and whole-genome sequencing, we provide the first insights into how MSSRF30T interacts with Pokkali rice in brackish conditions. Additionally, we have identified several genome features for a plant-associated lifestyle, previously unreported in this genus. These features include plant expansin, PEP-CTERM surface anchoring with exopolysaccharides, plant-associated Hrp-type three secretion system, ACC deaminase production, PQQ-independent glucose dehydrogenase pathway for phosphate solubilization, plant-derived sugar/organic acids utilization operons, carbohydrate utilization loci, and specific plant depolymerizing CAZymes. Notably, MSSRF30T lacks key genome features critical for the animal association. Overall, this study adds new knowledge in the field of Vibrio biology, especially Vibrio-plant beneficial interactions, a relationship largely underexplored.IMPORTANCEThe genus Vibrio comprises over 150 species of marine heterotrophic bacteria, many of which are opportunistic pathogens affecting humans and marine animals. Most research has predominantly focused on pathogenic Vibrio species, often overlooking the significance of other Vibrio species inhabiting other ecological niches, such as plants, a relationship largely uncharacterized. This study focused on V. porteresiae MSSRF30T and its relationship with brackish-grown Pokkali rice. We discovered that MSSRF30T possesses multiple plant growth-promoting traits, effectively colonizes roots, and enhances plant growth in brackish conditions. Additionally, MSSRF30T possesses several genome features commonly associated with plant-microbe interactions, previously unrecognized in Vibrio species, and lacks features typically associated with animal interactions, underscoring its specialized adaptation for plant niches. For the first time, this study highlights the beneficial interactions between Vibrio and plants, emphasizing their role in promoting plant growth and health in brackish environments.

Actinobacterial strains obtained from the rhizosphere of tomato (Solanum lycopersicum) plants were evaluated for their production of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCD) and plant growth regulators (PGRs). Here, we aimed to determine the effects of rhizosphere-competent (RC) and non-rhizosphere-competent (NRC) consortia on tomato growth under salt stress (200 mM NaCl) by assessing morphological, physiological, and biochemical mechanisms. Our greenhouse experiments revealed that inoculation with actinobacterial consortia significantly increased the length and biomass of shoots and roots compared to control plants; however, RC consortium demonstrated overall greater plant growth promotion efficacy, including higher biomass accumulation and improved root-shoot development than plants inoculated with NRC consortia under both normal and salt stress conditions. This suggests that the high rhizosphere competence is crucial for plant growth promotion and salt tolerance. Individually, isolate #36 (the PGR-producer) significantly improved plant growth and biochemical photosynthetic components (net photosynthesis and chlorophyll content index), while its combination with RC isolate #53 (the ACCD-producer) further enhanced salt stress resilience. In particular, inoculation with RC consortium of actinobacteria positively influenced photosynthetic parameters, priming plants to respond more robustly to salt stress, likely by efficiently activating antioxidant metabolism, detoxifying Na⁺, and enhancing polyamine, auxin, gibberellin, and cytokinin levels. Notably, tomato plants treated with isolates #36 (Streptomyces violaceus UAE1) and #53 (Streptomyces levis UAE1) exhibited a threefold reduction in endogenous ACC levels compared to salt-stressed controls, indicating effective ethylene regulation. This study is the first to demonstrate the synergistic effect of RC actinobacterial consortium in mitigating salt stress in tomato plants, highlighting their potential as bioinoculants for sustainable agriculture.