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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...
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Introduction
While co-inoculation with rhizobia and plant growth-promoting rhizobacteria (PGPR) can enhance soybean growth and nodulation, the interaction mechanisms between Bacillus velezensis 20507 and Bradyrhizobium japonicum USDA110 under varying nitrogen (N) supply levels (0–10 mmol/L) remain unclear. This study investigates how their synergis...
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Citations
... También se ha explorado el uso de recursos bióticos, como las rizobacterias promotoras del crecimiento vegetal (PGPR, por sus siglas en inglés, Plant Growth Promoting Rhizobacteria), que representan una alternativa para proteger a los cultivos y prolongar la calidad de frutos durante la precosecha y postcosecha (de Andrade et al., 2023;Saebi et al., 2023). Bacillus subtilis es una de las PGPR más estudiadas; esta bacteria es capaz de promover el crecimiento de las plantas y controlar fitopatógenos a través de diversos mecanismos como la solubilización de fósforo en suelo, la fijación biológica de nitrógeno, la síntesis de antimicrobianos, la producción de la fitohormona indol-3-acético (IAA) y la disminución de los niveles de etileno en plantas (Shahid et al., 2023). ...
La guanábana es un fruto climatérico altamente perecedero, lo que limita su comercialización y es por ello, que se buscan estrategias para prolongar su vida de anaquel. Considerando esto, el objetivo de esta investigación fue probar el efecto de un consorcio bacteriano de tres cepas de Bacillus subtilis aplicado en precosecha para evaluar los parámetros de calidad de los frutos en etapa postcosecha. Se seleccionaron diferentes etapas de desarrollo del fruto en el árbol para la aplicación (4, 8 y 12 semanas post-antesis), además de los frutos en madurez fisiológica ya cosechados. Se evaluaron los parámetros fisicoquímicos de firmeza, acidez titulable, pH, sólidos solubles totales de acuerdo con los protocolos de la AOAC. También se evalúo la expresión del gen que codifica para la enzima poligalactuonasa. Los resultados revelaron que el consorcio bacteriano tiene un efecto positivo en prolongar la vida de anaquel cuando se aplica en precosecha a las 12 semanas de desarrollo del fruto. Este estudio revela que es fundamental la selección de la etapa del desarrollo del fruto para lograr efectos positivos mediante la aplicación B. subtilis sobre la calidad de frutos con corta vida de anaquel como la guanábana.
... In addition, PGPR also regulates geochemical nutrient cycles, ensuring nutrient availability to plants and soil microbes 15 . Therefore, utilizing these beneficial rhizobacteria as bioinoculants can considerably enhance nutrient availability in soil, reduce reliance on chemical fertilizers, and encourage sustainable agricultural practices 16 . ...
The rhizosphere hosts a diverse group of beneficial bacteria that can serve as an alternative to chemical fertilizers. Exploring the potential traits of these bacteria can lead to sustainable farming practices, promoting crop yields while minimizing environmental impact. The present study was conducted to characterize and identify native plant growth-promoting bacteria (PGPB) from the rhizosphere of tomato plants cultivated in the organic state of Sikkim, India. Seventy bacterial strains were isolated from different tomato cultivation sites in Sikkim and characterized for their plant growth-promoting (PGP) traits. Out of these, eight potential bacterial strains were selected, and identified as Klebsiella variicola AST1, Bacillus cereus AST3, Enterobacter sichuanensis AST4, Enterobacter mori KH2, Bacillus cereus SG1, Enterobacter sichuanensis SG2, Enterobacter asburiae YG1, and Priestia aryabhattai YG2. Among them, Enterobacter sichuanensis AST4 demonstrated notable ammonia production (55.14 ± 0.03 mM), phosphate solubilization (564.6 ± 0.19 µgmL–1), and nitrogen fixation potential. Similarly, Klebsiella variicola AST1 exhibited the highest indole-3-acetic acid (IAA) production (125.33 ± 0.2 µgmL–1) during in vitro experiments. Likewise, Enterobacter sichuanensis SG2 displayed substantial gibberellic acid (GA3) production (18.3 ± 0.02 µgmL–1), and siderophore production (85%), against the uninoculated control. Greenhouse experiments further revealed that Klebsiella variicola AST1 significantly improved agronomic performance, with increases in plant height (70%), root length (86%), number of leaves (36.6%), and fresh and dry root weight (77% and 58.3% respectively), compared to the uninoculated control. These findings underscore the potential of rhizospheric bacteria from Sikkim’s organic tomato fields to enhance plant growth and agricultural productivity, promoting a sustainable crop production system.
... Ammonia, a product of nitrogen fixation, is essential for enhancing nitrogen availability in the soil, thus improving soil fertility and plant growth. 32 In addition, auxins like indole-3-acetic acid (IAA), play a crucial role in root elongation and development, which can significantly influence nutrient uptake and overall plant health. 33 The high levels of auxin production observed in Pseudomonas parafulva (B67) suggest that this strain has the potential to enhance root development and overall plant growth, a finding consistent with previous studies that highlight the auxin-producing ability of Pseudomonas species. ...
Rhizobacteria play a crucial role in enhancing plant growth and improving crop yield. This study focuses on the plant growth-promoting and biofertilizer potential of rhizobacteria isolated from the chickpea (Cicer arietinum) rhizosphere. The evaluation involved both primary and secondary screening processes to assess the key biochemical traits. The primary screening focused on ammonia and auxin production, where ammonia production enhances nitrogen availability for plants and auxins, particularly indole-3-acetic acid (IAA), contribute to root formation and overall plant growth. Secondary screening examined the production of siderophores and hydrogen cyanide (HCN). Siderophores facilitate iron uptake by plants, while HCN acts as a biocontrol agent by inhibiting soilborne pathogens. The study's findings showed that, among the five bacterial isolates one isolate (B67) had high auxin and siderophore-producing abilities it also exhibited ammonia and HCN producing abilities. Inoculation of this rhizobacterial isolate on chickpea seeds exhibited positive effects on seed germination and seedling growth. Isolate B67 has been identified as Pseudomonas parafulva using 16S rRNA gene sequencing. These findings suggest that Pseudomonas parafulva isolated from the chickpea rhizosphere possesses multiple plant growth-promoting traits positively influences growth of plants. Therefore, it might be used as an effective bioinoculant and biocontrol agent, offering a sustainable alternative to chemical fertilizers and pathogen management strategies.
... 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.
... Phylogenetic β-diversity analysis (UniFrac metrics; Figure 4g,h) and PCoA (Figure 4i,j) further confirmed the divergence of PGPR-treated communities from controls, with T3 strain eliciting the most distinct bacterial assemblage (PCoA axis 1: 40% variance). This aligns with prior observations of PGPR-driven microbiome specialization [39]. ...
Spent mushroom substrate (SMS) is the residual biomass generated after harvesting the fruitbodies of edible fungi. It is produced in large quantities and contains abundant nutrients. Plant growth-promoting rhizobacteria (PGPR) are a group of plant-associated microorganisms known for their ability to enhance plant growth, improve disease resistance, and boost soil quality. In this study, three PGPR strains with the highest plant growth-promoting potential were selected based on their ability to grow effectively in SMS extract. The SMS substrates were mixed with PGPR solutions and sterile water to establish a batch culture system. The mixture was initially incubated at 28 °C for 3 days, followed by continuous aerobic decomposition in a ventilated environment for 180 days. Based on the quality analysis of the PGPR-treated SMS, the 54-day treatment for transplanting blueberry seedlings was selected. The PGPR-treated substrates showed significantly higher TN, HN, and AP than controls (p < 0.05), suggesting a potential role of PGPR in enhancing nutrient availability. Alpha diversity index analysis revealed significant differences in microbial diversity between the PGPR-treated substrates and the control. Furthermore, the PGPR-treated substrates significantly influenced plant growth characteristics, soil nutrient content, and rhizosphere microbial diversity. Enhanced plant growth characteristics were strongly correlated with increased soil nutrient levels, suggesting a potential link between rhizospheric microbial communities and plant growth performance. This study provides a novel approach and experimental framework for the utilization of SMS and the development of PGPR-based biofertilizers, offering valuable insights into sustainable agricultural practices.
... 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.
