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Schematic representation of the steps required to isolate and characterize bacteria that promote plant growth.
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Rhizosheric bacteria with several abilities related to plant growth and health have been denominated Plant Growth-Promoting Rhizobacteria (PGPR). PGPR promote plant growth through several modes of action, be it directly or indirectly. The benefits provided by these bacteria can include increased nutrient availability, phytohormone production, shoot...
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The usage of inorganic fertilizer has been shown to have a negative impact. However, most farmers tend to use chemical fertilizers due to its significant useful effects on plants. This study aims to determine the influence of pelletized plant growth-promoting microbial consortium (PGPR) derived from fermented rice water in Pakchoy plants (Brassica...
Soil salinization poses a significant ecological and environmental challenge both in China and across the globe. Plant growth-promoting rhizobacteria (PGPR) enhance plants’ resilience against biotic and abiotic stresses, thereby playing a vital role in soil improvement and vegetation restoration efforts. PGPR assist plants in thriving under salt st...
Plant growth promoting bacteria (PGPB) or plant growth promoting rhizobacteria (PGPR) are bacteria that exist in the rhizospheres of plant soil and form symbiotic relationships with the plant.Some of the methods through which PGPR aid in plant growth is by playing a role in nitrogen fixation, phosphate solubilization, iron chelation, reduction of h...
Drought stress significantly impairs crop growth and productivity, threatening global food security. Plant growth-promoting rhizobacteria (PGPR) enhance crop stress tolerance through various physiological and molecular mechanisms, including regulation of nitrogen fixation, phosphate solubilization, plant hormone production, antioxidant system, nutr...
Micro-organisms and agriculture have always co-existed in nature in a mutually beneficial relationship. These microbes provide essential minerals and nutrients to the plants in exchange of food and shelter. Crop growth and development are closely related to the nature of the soil microflora, especially those in close proximity to plant roots, gener...
Citations
... The increased root weight is attributed to the improved grain yield structure as a result of inoculation with bacterial formulations. As a result of greater availability and more efficient uptake of nutrients by plants, there is an improvement in the yield structure of plants, which also directly translates into an increase in yield (de Andrade et al., 2023). A possibility to provide plants with a wide range of plant growth-promoting mechanisms is the interaction of different microorganisms within a bacterial consortium (Zhang et al., 2021;Santoyo et al., 2021). ...
... Mineral-solubilizing bacteria positively influence the biochemical content of plants by enhancing Zn and P uptake, which in turn improves chlorophyll synthesis, protein content, carbohydrate metabolism, antioxidant activity, phytohormone levels, nutrient use efficiency, and secondary metabolite production. This results in healthier plants with better growth, higher stress resistance, and improved overall productivity [76]. Therefore, the ability of the mineral-solubilizing bacterium P. aeruginosa to raise the carbohydrate and soluble protein content of the leaves of groundnut plants grown under diverse circumstances was evaluated at regular intervals of 30 days. ...
The excessive use of phosphorus (P) fertilizers increases crop production but can lead to P-induced zinc (Zn) deficiencies, making both nutrients unavailable to plants. Plant–microbe interactions, such as with Pseudomonas aeruginosa, can alleviate these constraints by solubilizing Zn and P in soil. A soil incubation study revealed that applying P. aeruginosa with farmyard manure (FYM) significantly increased Zn and P solubilization (6.86 mg/l; 14.83 mg/l) compared to control (3.15 mg/l; 13.67 mg/l). A field experiment evaluated the effects of P. aeruginosa on the biochemical composition of groundnut plants under five treatments. The T2, T3, and T4 treatments had the highest protein, carbohydrate, and chlorophyll levels, likely due to the heterogeneous activity of FYM and the mineral solubilizing ability of P. aeruginosa. Groundnut seeds from T3 (combined liquid inoculant and FYM) had the highest iodine (88.47 mg KOH/g), saponification value (195.56 mg KOH/g), and free fatty acid content (2.23 g oleic acid). The pH of the T3 soil decreased from 8.3 to 7.5, and significant increases were observed in electrical conductivity (from 2.88 to 0.30 dS/m), calcium carbonate (2.53–1.7%), organic carbon (0.39–1.91%), nitrogen (273.75–788.25 kg/ha), P (20.1–59.65 kg/ha), potassium (182.25–346.5 kg/ha), and Zn (1.53–7.24 mg/kg). The study suggests that the combined application of liquid formulants of P. aeruginosa with FYM is advantageous, as FYM supports microbial growth by providing essential nutrients for mineralization. Moreover, liquid inoculants formulated with polyvinylpyrrolidone as an osmo protectant demonstrated enhanced shelf-life and mineral solubilization, contributing to improved biochemical properties in groundnut plants.
... Ralstonia pickettii QL-A6, a low virulence gram-negative Bacillus, was isolated from the rhizosphere of tomato plants and successfully used to suppress bacterial wilt of tomatoes caused by Ralstonia solanacearum [7,8]. Many researchers have indicated that the most common bacterial species around roots isolated from the rhizosphere are bacteria belonging to the genus Bacillus, and the most famous Gram-positive species are Bacillus cereus and Bacillus subtilis [9], and are considered one of the most important plant growth promoting bacterial species (PGPR) due to their effectiveness in dissolving phosphates used as bio-fertilizers [10], in addition to their ability to produce iron-soluble siderophores and auxin phytohormone indole-3-acetic acid (IAA). They grow well on nutrient agar and can be motile with or without motile flagella [11]. ...
we collected sixteen samples of soil surrounding the rhizosphere zone to isolate and characterize rhizobacterial species based on biochemical tests, 16S rRNA gene primer amplification using PCR and nucleotide sequence analysis, and similarity to global isolates in the gene bank, Gram staining and biochemical tests. On the other hand, the results showed that root colonizing bacteria could produce different amounts of indole-3- acetic acid (IAA). Molecular analysis tests based on the 16S rRNA primer gene were carried out to characterize the isolated bacteria at the molecular level and showed 99% homology with Azotobacter tropicalis SC39, Azotobacter chroococcum A11, Bacillus subtilis N22 and Ralstonia pickettii ULM005, which are registered worldwide in GenBank. It should be noted that in the diagnostic isolate R. pickettii both A and T were deleted, G was replaced by C and T was added at position 508. In the B. subtilis isolate, the nitrogenous bases A, G and G were deleted and the nitrogenous base G was replaced by the base C. The data for the third isolate, A. tropicalis, showed deletion of the nitrogenous bases C and T and replacement of G by A and A by T. In the fourth isolate, A. chroococcum , deletion of the nitrogenous base, replacement of C by A and C by T and addition of G, T and A in three positions were observed. These will be used as the basis for future scientific experiments to develop new bio-fertilizers from the rhizobacteria studied for the production of environmentally sustainable crops.
... Pseudomonas produced the greatest amount of IAA (at all tryptophan concentrations, 50--500 µg/ml). On Muller-Hinton medium, antagonistic activity was examined against Aspergillus, Fusarium and Rhizoctonia bataticola, and the results revealed that Azotobacter (isolates AZT (3), AZT (13) and AZT (23)) as well as Pseudomonas (Ps (5)) and Bacillus (B (1)) antagonistized Aspergillus, Fusarium, and Rhizoctonia bataticola (de Andrade et al., 2023). The effects of isolated PGPR on the root and shoot length, seed germination, and chlorophyll content of spinach (Spinacia oleracea L.) were studied by Chowdhury et al. (2016). ...
Global agriculture currently suffers from pollution caused by the widespread use of chemical fertilizers and pesticides. These agrochemicals, when consumed in food, can harm human health (e.g. increasing risks of cancer and thyroiddisorders)and damage the environment by reducing soil fertility, among other effects. Thus, there is a high demand for biological agents, such as microorganisms, that could partially or fully replace these agrochemicals.Plant growth-promoting rhizobacteria (PGPR) are promising in this regard, as they can enhance plant growth and productivity sustainably.These bacteria promote plant growth and development through both direct and indirect mechanisms. Directly, PGPR increase plant growth by making phosphorus, nitrogen, and other essential minerals more available to plants, as well as by regulating plant hormone levels. Indirectly, PGPR inhibit pathogenic microbes that otherwise hinder plant growth and development, for instance, through the production of siderophores.In addition, PGPR show synergistic and antagonistic interactions with microorganisms within the rhizosphere and beyond in bulk soil, which indirectly boosts plant growth rate.Studies indicate that PGPR can improve plant health and yield across a variety of plant species, under both favourable and challenging conditions. As a result, PGPR have the potential to reduce the global reliance on harmful agricultural chemicals that disrupt environmental health. Additionally, the demand for PGPR as biofertilizers and biopesticides is growing globally, further highlighting their potential as powerful alternatives in sustainable agriculture.Numerous bacteria act as PGPRs, which have been described in the literature as effective in enhancing plant growth. In order to improve the efficacy of PGPRs, it is important to study their characteristics and mode of application since there isa gap between their mode of action (mechanism) for plant growth and their role as biofertilizers
... These genera are commonly isolated from the rhizosphere of plants in arid and semi-arid soils [34][35][36]; they are well known as halotolerant PGPR [10,[36][37][38] and our observations are in line with these earlier reports. PGPR play a vital role in stimulating plant growth and development in several ways [39][40][41][42]. In the present study, 66 isolates were assessed for the following PGP traits, including ACCD activity, IAA production, P-solubilization, N-fixation, and NH 3 production. ...
Halotolerant, plant growth-promoting rhizobacteria (PGPR) are known to alleviate plant growth under abiotic stresses, especially those isolated from saline arid soils. In this study, 66 bacterial isolates, obtained from various habitats in Saudi Arabia, were characterized for their plant growth-promoting (PGP) traits, and screened for heat and salt stress resilience. Finally, selected halotolerant PGPR strains were assessed for their potential to improve maize (Zea mays L.) growth under salinity stress using in vitro assays. Our results indicated that many isolates possessed key PGP traits such ACC deaminase, N-fixation, and phytohormone production. Additionally, several isolates were able to tolerate high temperatures, and 20 bacterial isolates were classified as halotolerant. Furthermore, among the isolates, Pseudomonas soyae (R600), Bacillus haynesii (SFO145), Salinicola halophilus (SFO075), and Staphylococcus petrasii (SFO132) significantly enhanced various maize growth parameters under salt stress conditions when compared to uninoculated plants. These halotolerant PGPR are good candidates to be explored as bioinoculants for sustainable agriculture under saline arid soil conditions.
... Similarly, strain Ch8 exhibits P solubilization and siderophore production capabilities, enhance the availability of essential nutrients such as P and Fe in the soil, thereby promoting plant growth (Hakim et al. 2021;Bargaz et al. 2021). Moreover, microorganisms can facilitate the dissolution of insoluble silicates in the soil by secreting organic acids, further improving nutrients absorption by plants (De Andrade et al. 2023). Taken together, these findings suggest that strain Ch8 could promotes Chuanxiong growth, especially in Chuanxiong rhizomes. ...
... The increase of NO 3 --N and NH 4 + -N in the soil of the Ch8 group could not only provide a direct source of N for Chuanxiong but also promote N recycling through the action of microorganisms. As reported, LMWOAs can dissolve insoluble minerals in the soil, such as insoluble silicates (Si), and increase availability of essential nutrients like K and Si (De Andrade et al. 2023). Our study showed that the strain Ch8 had a high ability to secrete LMWOAs (Tables S1). ...
Aims
This study aimed to investigate potential benefits and mechanism of applying Cd-resistant Proteus mirabilis Ch8 to Ligusticum sinense cv. Chuanxiong (Chuanxiong) cultivation. Specifically, we sought to evaluate its effects on plant growth, Cd accumulation, active ingredient content, soil fertility, and rhizosphere microbial community composition.
Methods
A field experiment was conducted with two treatment groups: control group (CK) and Ch8 treatment group. In October, the rhizosphere of Chuanxiong was inoculated with either LB medium (CK) or Ch8 bacterial solution. Plant samples were collected in March of the following year. We measured biomass, Cd content, active ingredient content, rhizosphere soil fertility, and microbial community composition were determined.
Results
Inoculation with Ch8 significantly enhanced the growth of Chuanxiong Rhizomes while decreasing Cd accumulation. Particularly, compared to the CK group, the Ch8 treatment significantly increased the dry weight by 51.99% and decreased the Cd content by 30.62% of Chuanxiong. Additionally, Ch8 effectively inhibited Cd bioaccumulation and translocation in Chuanxiong. Notably, the content of ferulic acid (FA), a key active ingredient, significantly increased by 94.47% in the Ch8 group. Soil analysis revealed that Ch8 application significantly increased the contents of N, P, and K, as well as the residual Cd content in the soil. Furthermore, the structure and function of the rhizosphere microbial community were significantly altered in the Ch8 group. Enrichment of glutathione metabolism and phenylalanine metabolism-related functions was observed, which might contribute to the enhanced accumulation of active ingredients.
Conclusions
Ch8 not only promoted the growth and active ingredient content of Chuanxiong but also reduced Cd accumulation in the plant. These findings provide a scientific basis for utilizing Cd-resistant bacterium to mitigate Cd contamination, improve the quality of medicinal plants, and ensure their sustainable development.
Graphical Abstract
Article Highlights
• Ch8 significantly enhances growth and reduced Cd enrichment in Chuanxiong.
• Inoculation with Ch8 significantly increased active ingredient content in Chuanxiong.
... PGPR employ a variety of mechanisms to promote plant growth, primarily through enhanced nutrient acquisition and modulation of plant hormone signaling, thereby mitigating stress perception. Nutrient availability is increased through processes such as nitrogen fixation [7][8][9], solubilization of inorganic phosphate [10], and the production of high-affinity iron-chelating molecules known as siderophores [11,12]. Furthermore, PGPR can influence root architecture, improving water and nutrient uptake [13] by stimulating root elongation and lateral root development [14][15][16][17][18][19]. ...
Water scarcity can negatively affect crop yield, posing a significant threat to global food security, such as drought. Plant growth-promoting rhizobacteria (PGPR), either as single strains or synthetic communities (SynComs), has shown promise in alleviating drought stress in various plant species. In this study, we examined the effects of water limitation on Salvia officinalis and the potential of a SynCom composed of five phosphate-solubilizing, auxin-producing, and/or nitrogen-fixing Gram-negative bacteria to enhance plant growth and drought tolerance. Plant growth, morphology, physiology, and leaf metabolomic profiles were assessed using a combination of physiological measurements and LC-MS untargeted metabolomics. Mild water stress induced a conservative water-use strategy in S. officinalis, characterized by increased root-to-shoot ratio and altered leaf morphology, without compromising photosynthetic performance. SynCom inoculation under well-watered conditions elicited drought-like responses, including transient reductions in stomatal conductance. Leaf metabolomic analysis revealed that inoculation influenced the abundance of several metabolites, including biogenic amines and dipeptides, under both irrigation regimes. Notably, drought stress and SynCom inoculation increased histamine and α-ketoglutaric acid levels, highlighting potential impacts on food quality. Under reduced irrigation, inoculation further modulated leaf morphology and biomass allocation, promoting thicker leaves and increased root biomass allocation. These results demonstrate the ability of the SynCom to modulate plant physiology and metabolism in response to both optimal and reduced irrigation, potentially enhancing drought resilience without directly improving growth. The study also highlights the complex interactions among microbial inoculation, plant stress responses, and leaf metabolite profiles, emphasizing the importance of considering the effects on the production of bioactive compounds when developing microbial inoculants for edible plants.
... Microbial consortia made up of many synergistic species may be used to increase efficacy and avoid resistance in place of single strain of PGPR's. By combining PGPR's with nitrogen-fixing bacteria, mycorrhizal fungi, or biocontrol fungi, a more robust microbial ecology may be produced, lowering the likelihood of resistance [182]. Beneficial features in PGPR's strains may be made more stable by genetic engineering. ...
The hap hazardous and inappropriate application of pesticides and their deposition in the soil lowers agricultural productivity and increases disease tolerance to these pesticides. The pesticide treatment at recommended and higher dosages causes a severe reduction in the numbers of nitrogen-fixing, phosphate, and zinc-solubilizing microbial communities. The uptake of pesticides by plants adversely affects the growth and productivity of crops, electron transport reactions of chloroplasts, and reduction in antioxidant defense enzymes. These are elements that agronomists find quite disturbing in intensive cropping systems under changing climatic conditions. Plant Growth-Promoting Rhizobacteria (PGPR) in the rhizosphere degrades the pesticide and uses it as a nutrient source for their growth. They are capable of producing different types of growth-enhancing bio-active molecules, including plant-hormones such as auxins, cytokinins, gibberellins, etc. PGPR are known to solubilize insoluble phosphate and zinc, indirectly enhancing plants' growth and expansion by synthesizing siderophore production. These numerous PGPR’s activities enhance the soil's fertility, soil health, and functioning, which either directly or indirectly gain plant growth in normal and pesticide-stressful conditions. Since pesticides have disastrous effects on plants and rhizosphere biology, there is a growing interest in a variety of stress-resilient PGPR’s. Their subsequent use in contemporary agriculture for pesticides breakdown highlights the need of promoting pesticide stress tolerance. The functions of soil-dwelling PGPR’s in reducing pesticide stress, the supply of nutrients (nitrogen fixation and phosphorus solubilization), the generation of phytohormones, and the variables that may significantly impact their efficacy. The role of pesticide-tolerating PGPR’s and the molecular pathways underlying the rhizobacteria's development of pesticide tolerance needs more investigations. Therefore, this analysis fills the void and provides an overview of PGPR's as a bio-fertilizer for agricultural sustainability under agro-chemicals stressed condition. Giving a better understanding how PGPR’s tolerates and degrade agro-chemicals reduces environmental pollution brought on by overuse of pesticides increasing plant nutrient availability by means of phosphate and zinc solubilization, indole acetic acid production and etc. This review primarily focuses on the significance and necessity of pesticide-tolerant PGPR’s for environmentally responsible and sustainable practices in our farming systems, particularly in pesticide-stressed conditions that will likely worsen soon due to the pesticides' residual effects. Therefore, fostering plant well-being and offering a sustainable substitute for artificial fertilizers.
... In addition to the ability of rhizosphere bacteria to fix nitrogen, they also have other functions, such as solubilizing phosphorus and producing plant growth stimulants, such as IAA and gibberellin to increase crop productivity (Saeed et al. 2021;de Andrade et al. 2023;Cẩm et al. 2023). In this study, 3 bacterial strains of BĐ2.2, BĐ2.3.3, and BĐ2.3.1 had the capacity to fix nitrogen and solubilize phosphate. ...
Chi NTY, Minh NLK, Thi QVC. 2025. Isolation and characterization of plant growth-promoting rhizobacteria from wild rice (Oryza rufipogon) in the Mekong Delta, Vietnam. Biodiversitas 26: 1221-1228. Rhizospheric bacteria play a very crucial role in crops, especially rice. In contrast to cultivated varieties, wild rice (Oryza rufipogon), which is abundantly found in Mekong Delta canals, may have distinct rhizobacterial populations. Therefore, the objective of this work was to isolate and characterize Plant Growth-Promoting Rhizobacteria (PGPR) from wild rice with the characteristics of nitrogen fixation, phosphate solubilization, and IAA synthesis. A total of 12 bacterial strains, including seven bacterial strains of nitrogen-fixation and five strains of phosphate-solubilizing microbes, from four rhizospheric soil samples of wild rice in Tien Giang and Vinh Long provinces of the Mekong Delta, Vietnam. The results showed that strain B?1.2 had the highest nitrogen fixation activity with NH4+ content of 0.281±0.007 mg/L. In contrast, strain B?1.3, had the highest phosphorus solubilizing ability with a halo diameter of 1.123 ± 0.025 mm. Also, the finding showed that six out of twelve bacterial strains were capable of synthesizing IAA (Indole-3-Acetic Acid), of which strain B?2.3.1 produced the highest IAA with a concentration of 0.053 ± 0.001 mg/L after 8 days of bacterial inoculation. In particular, B?2.3.2, B?1.3, and B?2.4 simultaneously exhibited the ability of nitrogen fixation, phosphate solubilization, and IAA synthesis. The strain B?1.3 was identified as Stenotrophomonas sp. based on colony morphology, biochemical characteristics, and 16S rRNA gene sequencing with 91.74% similarity. To our knowledge, this is the first report of isolation of rhizospheric bacteria from O. rufipogon with the characteristics of nitrogen fixation, phosphorus solubilization, and IAA production in the Mekong Delta, Vietnam.
... Abiotic stress factors, such as salinity, drought, extreme temperature, heavy metals, and waterlogging, have become more frequent and severe because of global climate change, resulting in reduced crop growth and productivity [1,2]. According to estimates, abiotic stress is responsible for the loss of more than 50% of agricultural yields, and salt stress alone results in a 1-2% annual loss in arable land [3,4]. ...
... Environmentally friendly strategies, such as applying plant growth-promoting rhizobacteria (PGPRs), are essential for tackling such stressful conditions and enhancing crop yields in the future [2]. Various direct and indirect processes have shown that PGPRs develop symbiotic relationships with plants and support plant growth under stressful conditions [10]. ...
Beneficial microbes enhance plant growth and development, even under stressful conditions. Serratia fonticola (S1T1) and Pseudomonas koreensis (S4T10) are two multi-trait plant growth-promoting rhizobacteria (PGPRs) that are resistant to saline conditions. This study evaluated the synergistic effect of these PGPRs on mitigating salinity stress (200 mM) in Cucumis sativus. Presently, the synergistic effect of both strains enhances the plant growth-promoting attributes of cucumber, and the growth parameters were significantly higher than those of uninoculated plants. The PGPR-treated plants revealed a significantly higher biomass and improved chlorophyll content. The inoculation of S1T1 and S4T10 and the synergistic effect of both promoted 23, 24, and 28% increases, respectively, in the fresh biomass and 16, 19.8, and 24% increases, respectively, in the dry biomass. Similarly, S1T1 and S4T10 and their synergistic effects led to 16.5, 28.4, and 38% increases, respectively, in the water potential and 18, 22, and 28% decreases, respectively, in abscisic acid (ABA). A reduction in the electrolytic leakage (EL) was additional proof of successful PGPR activities. Similarly, a decrease in the antioxidant levels, including those of malondialdehyde (21–30%), hydrogen peroxide (19–38%), and superoxide anions (24–34%), was observed, alongside an increase in antioxidant enzymes such as catalase (22–29%) and superoxide dismutase (17–27%). Additionally, the synergistic inoculation of the PGPRs enhanced the NaCl stress tolerance by upregulating the expression of the ion transporter genes HKT1 (1–2-fold), NHX (1–3-fold), and SOS1 (2–4-fold). Conclusively, the synergistic effect of the multi-trait PGPRs significantly enhances C. sativus L. growth under salt stress.
