Phosphate Solubilizing Bacteria Research Articles

Isolation and characterization of phosphate solubilizing bacteria from the rhizosphere of lentil (Lens culinaris M.) collected from Hagere Mariam district, Central Ethiopia.

Phosphorus plays a crucial role in regulating many of the plant's metabolic activities by enhancing physiological functions and stimulating biological activities such as nodulation, nitrogen fixation, and nutrient uptake in the soil rhizosphere environment. Inoculants of phosphorus solubilizing bacteria serve as an eco-friendly alternative technology that positively influences both soil sustainability and plant growth. The majority of North Shewa highland areas are characterized by low available phosphorus, primarily acidic, and exhibit strong phosphorus absorption. The objective of this study was to isolate and identify phosphorus solubilizing bacteria from the rhizosphere of lentils and characterize their phosphate solubilizing activity. The cultural, biochemical, physiological microbial analysis was conducted in the microbiology laboratory, department of biology. Pikovskaya's medium was utilized for the isolation, screening, and maintenance of phosphate solubilizing bacteria. Phosphate Solubilizing Bacteria were isolated using tri-calcium phosphate as the sole source of phosphorus in indicator plates. Fifteen phosphate solubilizing bacteria were isolated from lentil rhizosphere soil samples, among which six were the most efficient phosphate solubilizers designated as PSBYE, PSBYR, PSBYM, PSBYL, PSBW, and PSBSW. All isolates notably solubilized tri-calcium phosphate compared to the uninoculated control. The highest phosphorous solubilization was observed from the isolate PSBYL, with a value of 10.61mg/50ml, followed by PSBW with a value of 9.08 mg/50ml. The decrease in pH value correlated with the levels of tri-phosphate solubilization in the PVK broth by the PSB isolates. The pH dropped to 4.64 from the initial pH of 7.2 when grown in the broth, which suggests that the production of organic acids is likely the primary mechanism for phosphate solubilization.

Soil Microbial and Metabolomic Shifts Induced by Phosphate-Solubilizing Bacterial Inoculation in Torreya grandis Seedlings

Phosphorus is crucial for plant growth and development, but excess fertilizer not absorbed by plants often binds with metal ions like iron and manganese, forming insoluble compounds that contribute to soil environmental pollution. This study investigates the impact of Burkholderia sp., a phosphate-solubilizing bacterium utilized as a biofertilizer, on the fertility of T. grandis soil, alongside the associated shifts in soil metabolites and their relationship with microbial communities after inoculation. The soil microbial community structures and metabolite profiles were analyzed via amplicon sequencing and high-resolution untargeted metabolomics. The inoculation of phosphate-solubilizing bacteria led to a significant (p < 0.05) enhancement in total phosphorus, potassium, and nitrogen concentrations in the soil, with a marked increase in available phosphorus in bulk soil (p < 0.05). Moreover, the microbial community structure exhibited significant shifts, particularly in the abundance of bacterial phyla such as Acidobacteria, Chloroflexi, Proteobacteria, and the fungal phylum Ascomycota. Metabolomic analysis revealed distinct metabolites, including fatty acids, hormones, amino acids, and drug-related compounds. Key microbial taxa such as Chloroflexi, Proteobacteria, Acidobacteria, Verrucomicrobia, Mucoromycota, and Ascomycota indirectly contributed to soil phosphorus metabolism by influencing these differential metabolites. In conclusion, the application of phosphate-solubilizing bacteria offers an innovative approach to improving soil quality in T. grandis, promoting phosphorus utilization efficiency, and enhancing soil ecosystem health by optimizing microbial communities and metabolite compositions.

Pengaruh Campuraan Bakteri Pelarut Fosfat dan Bakteri Penambat Nitrogen terhadap Pertumbuhan Tanaman Jagung pada Lahan Kelapa Sawit (Elaeis guineensis Jacq.) Menghasilkan

Intercropped farming utilizez used open spaces as an alternative to making empty land more productive. In certain periods, oil palm plantations have open spaces that can be used for planting intercropped plants. The problem is, in general, that oil palm plantations are planted on marginal land, such as inceptisol that is weak in phosphate, so if they are planted with palm oil, it is necessary to provide fertilizer with the main macro element content for palms to grow optimally, such as phosphorus (P) and nitrogen (N). Efforts can be made to meet the P and N requirements by applying combinations of microorganisms such as phosphate solubilizing bacteria (PSB) and nitrogen-fixing bacteria (NFB). The study aims to find out the effect of various dosages of PSB and NFB combinations on the growth and yield of corn crops, as well as the effect of corn crops on the growth and physiology of palm oil crops. The experiment was conducted at the Ciparanje Experimental Farm, Faculty of Agriculture, Padjadjaran University, January to April 2024. The study used a randomized block design (RBD) with six treatments repeated four times. The treatments included the application of a combination of Pseudomonas sp. and Azotobacter sp., which included: 10 kg/ha of PSB and NFB per plant, 20 kg/ha of PSB and NFB per plant, 30 kg/ha of PSB and NFB per plant, 40 kg/ha of PSB and NFB per plant, and 50 kg/ha of PSB and NFB per plant. Experimental results showed that the PSB and NFB mixture increased crop height 5.28%, stem diameter 3.19%, cob length 9.2%, cob diameter 9.8%, dried weight by 100 seeds 14.5%, and dried weight by corn plant 33.46%. The 40 kg/ha and 50 kg/ha dose of PSB and NFB per plant is the most efficient dose for the growth and of palm oil crops producing 2.

Impact of Combining Bio-Inoculants along with Inorganic Fertilizers on Soil Biological Characteristics in Transplanted Rice (Oryza sativa L.) Crop

A field experiment was carried out during the Kharif season in the year 2022 to assess the impact of inorganic fertilizers along with Bio-inoculants on soil biological properties in rice (Oryza sativa L.). The experiment consists of seven treatments viz., T1 Control, T2 100% RDF (150, 60, 40 N2, P2O5, K2O kg ha-1), T3 80% RDF + 10 kg BGA ha-1 Soil application + PSB (Phosphate solubilizing bacteria) 3kg/ha, T4 60% RDF + 10kg BGA ha-1 Soil application + PSB, T5 80% RDF + 500kg Azolla ha-1 Soil application +PSB, T6 60% RDF + 500kg Azolla ha-1 Soil application +PSB and T7 10kg BGA ha-1 Soil application + 500kg Azolla ha-1 Soil application + PSB were comprised in Randomized Block Design with three replication. The incorporation of inorganics, Azolla PSB, and BGA (bio-inoculants) actively activated microbial activities, resulting in a greater increase in the populations of total bacteria, actinomycetes, and fungi was observed throughout all growth stages, regardless of the treatments applied, when compared to their initial densities. This phenomenon supports the notion of a stronger rhizosphere effect. This trend aligns with the rise in organic carbon content. Moreover, soil dehydrogenase, alkaline phosphatase activities, along with microbial biomass carbon, displayed an upward trend in tandem with the progressive growth phases of the rice plant.

Plant growth promoting Rhizobacteria for sustainable tomato production

Numerous phosphate solubilizing bacteria (PSB) are found in the rhizosphere, benefiting the host plant in different mechanisms and promoting sustainable agriculture. They improve soil fertility with minimum cost requirements using an eco-friendly approach, which is an essential attribute for small-scale farm production. Thus, isolation, characterization, and evaluation of symbiotic effectiveness are hierarchical procedures to develop bioinoculants. Using a dual (plate and liquid medium) screening technique and a greenhouse trial, four potential PSB strains (Mk-1–25, Mk-13–16, Mk-20–7, and Mk-20–20) were selected from tomato rhizosphere soil. All isolates exhibited the following traits: produced colony clear-zone, lowered liquid medium pH, gram-positive, produced urease and IAA, dissolved substantial P from various substrates, symbiotically effective, and improved tomato growth and yield. Taxonomically, they belong to Bacillus and Priestia species (i.e., Mk-1–25 Bacillus halotolerance, Mk-13–16 Bacillus amyloliquefaciens, Mk-20–7 Bacillus megaterium, and Mk-20–20 Priestia megaterium). Among the current strains, Bacillus halotolerance recorded higher SI (3.11), was able to grow in extreme conditions (10% salt, up to 45 °C), produced HCN and siderophore, and improved tomatoes’ shoot length and weight, in contrast, Mk-20–20 produced HCN, siderophore, was able to fix nitrogen, improved tomato germination, shoot dry weight, and fruit weight. Various P-supplements (Ca3(PO4)2, bonemeal, FePO4, AlPO4, compost, and DAP fertilizer) were added to induce tomato-strain symbiotic interaction; hence, compost substantially promoted the interaction and resulted in higher symbiotic effectiveness. Ca3(PO4)2 was a good media composite preferred by most PSB strains; consequently, a higher concentration (219 µg/ml) of dissolved P was recorded from the liquid medium after 10 days of incubation than other substrates. Based on the data obtained from laboratory and greenhouse trials, the current strains were found to be potential candidate. Future work should confirm their efficacy at the field level using model host crops at different sites to recommend them as farm inputs and biofertilizer.

Outside-in enhancement of phosphate solubilizing bacteria by sludge biochar for phenol remediation in soil: Pollution stress reduction, electron transfer gain and secretion regulation

The high toxicity of phenol poses a significant barrier to bacterial bio-removal capacity. This study innovatively proposes the utilization of sludge biochar (SB) to embed phosphate-solubilizing bacteria (CZB1), creating a composite system (SB-CZB1) that enhances the bio-removal efficiency of phenol. The research findings indicate that after being embedded with biochar, Phosphorus solubilizing bacteria (PSB) achieved a significant enhancement (49.7 %-67.0 %) in phenol removal efficiency across different concentration gradients (1500, 2000, 2500 mg/L). SB component in the SB-CZB1 composite system provides a stable and favorable growth environment for CZB1, significantly enhancing microbial metabolic activity. Notably, it stimulates CZB1 to secrete succinic acid and malic acid (with increases of 3.8 % and 23.9 %, respectively), effectively mitigating the detrimental effects of phenol toxicity on microorganisms. Three-dimensional fluorescence and electrochemical analysis demonstrate that SB not only exhibits exceptional electrochemical performance but also stimulates CZB1 to generate redox-active substances (quinone components in humic acid). The electron transfer rates between microorganisms and phenol in the SB-CZB1 system are 9.75–21.71 times and 23.94–63.95 times higher than those in SB and CZB1 alone, respectively. Meanwhile, the abundant oxygen-containing functional groups (COH/COC, COOH, CO) on the surface of SB-CZB1 play a pivotal role in the adsorption and removal of phenol. Furthermore, pot experiments further reveal that the SB-CZB1 composite system significantly enhances the removal efficiency of phenol in soil (98.1 %). Additionally, the application of SB-CZB1 effectively modulated soil properties, notably increasing available potassium and available phosphorus content by 40.86 % and 136.69 %. This application not only enriched soil microbial diversity but also promoted the proliferation of native organic pollutant remediation bacteria in the soil. Notably, the proliferation of Bacillus species affiliated with CZB1 was the most significant, increasing by 82.1 %. This result confirms that biochar embedding technology effectively enhanced the colonization of CZB1 in the soil, thereby significantly accelerating the bio-removal process of phenol.

Adapting fodder oats to climate change: Enhancing growth, yield, and microbial dynamics under elevated CO2 and temperature

The effects of elevated atmospheric carbon dioxide concentration (e[CO2]) and temperature (e°T) on various traits of oat (Avena sativa L.) varieties using open-top chambers (OTC) were investigated. A simulated environment was created for the experiment i.e., ambient temperature and CO2 (a°T + a[CO2]); elevated temperature (3 °C > ambient temperature) (e°T); elevated CO2 (550 ± 50 ppm) (e[CO2]); and a combination of ambient temperature with elevated CO2 (a°T + e[CO2]), for accessing the effect of e°T and e[CO2] on oats. a°T + e[CO2] increased plant height to 121 cm compared to 114 cm in a°T + a[CO2] and 111 cm in e°T + e[CO2]. Seed weight was highest in a°T + e[CO2] (3.09 g) compared to 2.53 g in a°T + a[CO2] and 2.60 g in e°T + e[CO2]. Leaf number and tillers were significantly higher in a°T + e[CO2] (61.4 leaves, 10 tillers) than in a°T + a[CO2] (27.6 leaves, 5.6 tillers) and e°T + e[CO2] (44.3 leaves, 6.93 tillers). Chlorophyll content was highest in a°T + e[CO2] (5.13 mg/g) compared to 3.61 mg/g in a°T + a[CO2] and 1.47 mg/g in e°T + e[CO2]. In contrast, germination rate was best in a°T + a[CO2] (81.6 %) compared to e°T + e[CO2] (60.3 %) and a°T + e[CO2] (63.1 %). Malondialdehyde (MDA), a stress marker, was significantly higher in e°T + e[CO2] (1.35 nmol/g) compared to a°T + a[CO2] (0.299 nmol/g). Membrane stability index (MSI) was lowest in e°T + e[CO2] (13.2) compared to 20.9 in a°T + a[CO2], indicating greater stress under e°T + e[CO2]. Starch content in a°T + e[CO2] (14.6 %) was more than double that of a°T + a[CO2] (7.09 %). Microbial activity also showed significant differences. Dehydrogenase was highest in e°T + e[CO2] (13.86 µg/g/day) compared to a°T + a[CO2] (8.80) and a°T + e[CO2] (12.62). Total bacterial count (TBC) increased in e°T + e[CO2] (72) compared to a°T + a[CO2] (61). Similarly, phosphate-solubilizing bacteria (PSB) and fungi (PSF) were highest in e°T + e[CO2] (PSB: 104.5, PSF: 8.5) compared to a°T + a[CO2] (PSB: 75.0, PSF: 4.0). Rhizobium and Azotobacter counts were elevated in a°T + e[CO2] (95 and 94) compared to a°T + a[CO2] (72.5 and 42.0), showing a strong positive impact of e[CO2] on microbial populations. Specific oat varieties such as JHO-2000–4 and JHO-99–2 performed best under these conditions, showing higher yields and better stress tolerance. While e[CO2] offers substantial benefits to oat plant growth and soil microbial activity, the additional stress from e°T complicates these benefits.

Integration of organic amendments and phosphate-solubilizing bacteria improves wheat growth and yield by modulating phosphorus availability and physiological reponses

Saline calcareous soil presents significant challenges for crop production due to its poor nutrient availability and adverse effects on plant growth. Hence this study aimed to investigates the impact of integrating organic amendments—specifically Moringa seed residues, biogas manure, and vermicompost (Ver)—with and without phosphate-solubilizing bacteria (PSB), alongside two types of phosphatic fertilizers, ordinary super phosphate (OSP) and rock phosphate (RP), on the growth, yield, and nutrient uptake of wheat plants in saline calcareous soil conditions. The results indicate that the combined application of Ver + PSB, particularly when paired with OSP, consistently yields superior outcomes across all measured parameters, followed by Ver + PSB with RP. Notably, the Ver + PSB with OSP treatment exhibits the highest values across several key parameters: chlorophyll levels (chlorophyll a at 1.8, chlorophyll b at 0.84, and carotenoids at 0.72 mg g−1f wt), proline at 38.5 μg g−1 DW, relative water content at 80.76%, membrane stability index at 67.62%, as well as net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (gs). Furthermore, this treatment showcases the highest antioxidant enzyme activities (Superoxide dismutase, SOD at 9.27 A564 min−1 g−1 protein, Catalase, CAT at 78.53 A564 min−1 g−1 protein, Peroxihdase, POX at 1.86 A564 min−1 g−1 protein), as well as NPK content and uptake in wheat straw and grains. Additionally, it leads to significant increases in wheat growth parameters, including plant height, straw weight, grain weight, 1000 grain weight, and protein content. However, it also results in a notable decrease in other parameters such as total soluble sugars and nonenzymatic antioxidants (Ascorbate, AsA; Total glutathione, GsH; and α-Tocopherol, α-TOC).

Co-Inoculation of Phosphate-Solubilizing Bacteria and Rhizobia Increases Phosphorus Availability and Promotes the Development of Forage Legumes

Tropical grassland soils, especially those with alkaline properties, often exhibit limited phosphorus availability due to its precipitation in insoluble forms. Phosphate-solubilizing bacteria (PSB) and rhizobia have demonstrated their potential to enhance the availability of this nutrient and promote the growth of forage legumes. This study, conducted under controlled conditions in a mesh house, evaluated the effect of co-inoculation with PSB, including Micrococcus sp. Sfcm-14-01, Agrobacterium sp. Sfl-043-09, and Enterobacter sp. Sfcm-014-02 and Sfcm-054-06, along with rhizobia (Ensifer terangae R1-012-02 and Bradyrhizobium glycinis Rcm-025-01), under different levels of phosphorus fertilization on the legumes Leucaena leucocephala and Centrosema macrocarpum. The results indicate significant increases in various growth parameters, such as chlorophyll levels (SPAD), biomass (dry weight of roots and aerial parts) (mg), the foliar phosphorus concentration (ppm), and the concentration of available phosphorus in the soil, particularly under low-phosphorus fertilization conditions. The highest level of available phosphorus in the soil was achieved with 75% of the recommended fertilization dose, resulting in concentrations of 13.73 ppm for L. leucocephala and 7.69 ppm for C. macrocarpum, representing increases in phosphorus availability of 170.81% and 240.27%, respectively, compared with no fertilization or inoculation. These findings suggest that the co-inoculation of PSB and native rhizobia is a promising strategy to enhance the biomass productivity and mineral content of forage in tropical grazing systems, especially under phosphorus-limited conditions.

Enhanced Plant Growth Through Composite Inoculation of Phosphate-Solubilizing Bacteria: Insights from Plate and Soil Experiments

Excessive application of phosphorus (P) fertilizers does not alleviate P deficiency in soils and may cause water eutrophication. The available P in acidic soils is bound to minerals, such as iron and aluminum, in forms that are difficult to utilize by plants. The low availability of P is detrimental to soil health and crop growth. To address the P imbalance in the soil, different bioremediation techniques, such as phosphate-solubilizing bacteria (PSB) application, have been employed. However, the systematic analysis of the effects of composite inoculation of PSB on crops remains elusive. In this study, the effects of composite-inoculated PSB on plant growth were systematically evaluated by two scales: plate experiment and soil test. This study employed six different strains of PSB including Lelliottia amnigena 1-1 (A), Kluyvera intermedia 1-2 (B), Pseudomonas tolaasii 1-6 (C), Burkholderia cepacia 2-5 (D), Pseudomonas frederiksbergensis 2-11 (E), and Pseudomonas rhodesiae 2-47 (F). Among the 57 different combinations of these strains, four combinations (AE, AF, ADF, and AEF) indicated higher phosphate-solubilizing abilities than the single strains. These combinations were used for subsequent experiments. The plate experiment revealed that composite strains were more effective than single strains in promoting the growth and development of seedlings and roots of oilseed rape. Furthermore, AE, AF, and AEF combinations indicated excellent growth-promoting effects. Moreover, the soil test revealed that the composite inoculation of AE and AEF significantly enhanced biomass accumulation and root development in oilseed rape. The increased growth-promoting effects of the composite strains were observed to be associated with to their phosphate-solubilizing capacities. Both scales confirmed that compared to single inoculation, composite inoculation of PSB is more beneficial for plant growth. This study provides composite inoculation materials and foundational data to support the bioremediation of P imbalance in soil.

Effect of Liquid Microbial Consortium on Physio Chemical Properties of Rice Field (Oryza Sativa) in a Vertisol

A study was conducted during kharif 2020 on "Effect of liquid microbial consortium (Azotobacter, Azospirillum, PSB (Pseudomonas mallei, Pseudomonas cepaceae, Penicillium sp.) and KSB) on physio chemical properties and microbial population of rice field (Oryza sativa) in a Vertisol" at the Indira Gandhi Krishi Vishwavidyalaya's Research cum instructional farm in Raipur (C.G.). Experiment included seven treatments viz. control (no fertilizer, no liquid NPK microbial consortia), two independent applications of 75 % RDF (90:45:30) and 100% RDF ((120: 60: 40) N, P2O5, and K2O kg ha-1 and four various combinations of seed and soil application of liquid NPK microbial consortia. Seed coating with NPK consortia @5ml kg-1, with 75% and 100% RDF and Seed coating with NPK consortia @5ml kg-1 + Soil application of NPK consortia @3 L ha-1 at 21 DAS with 75%RDF and 100%RDF. In the experiment, liquid biofertilizer products, such as liquid microbial NPK consortia were used. The population of Azotobacter, Azospirillum, phosphorous solubilizing bacteria (PSB), potassium solubilizing bacteria (KSB) and total bacterial population were significantly influenced by application of consortia as seed treatment @ 5ml kg-1 only and by a combination of seed treatment @ 5ml kg-1 seed + soil application @ 3 L ha-1 at 21 DAT with 75 or 100 % recommended dose of fertilizers and showed statistically significant higher microbial population in comparisons with the treatments of untreated alone applications of 75 or 100 % RDF. The results showed that the soil reaction, (pH) salt concentration (Electrical conductivity) and organic carbon status were not significantly influenced by the different treatments of fertilizer levels and microbial consortia applied. Slight decrease in the soil reaction (pH) and slight increase in the OC status after the harvesting of rice were observed from their initial soil values (before application of treatments). It might be due to the addition of organic matter as plant residues (straw and roots) of rice crop gown in the field. As compared to untreated- control (T1) a slight decrease in pH and increase in organic carbon content due to application of fertilizer and microbial consortia were also recorded. The residual available nitrogen in the soil after the harvesting of rice was not significantly influenced by the fertilizer levels and NPK consortia applied. The initial status of the experimental soil was low for available nitrogen (224 kg ha-1), medium for available phosphorus (24.5 kg ha-1) and high for available potassium (384 kg ha-1). Due to the addition of nitrogen through the fertilizer (90-120 kg ha-1) and less uptake of native nitrogen from the soil, a marginal increase in the residual available N in the soil from the initial level was observed in all treatments except the control (no fertilizer, no consortia). The residual status of available potassium was also not significantly influenced by the applied fertilizer doses and NPK consortia. A marginal decrease in the residual available K status after the harvesting of rice was observed in all treatments. A decrease was found in the control plot. A decrease in the K status (from the initial level) was observed less where a full dose of NPK fertilizers (100%) was applied with the NPK consortia. Ramlakshmi et al. [1], also observed slight reduction in soil pH and increase in organic carbon content in biofertilizer inoculated treatments as compared to the un-inoculated control soil [2].

Halophilic Phosphate-Solubilizing Microbes (Priestia megaterium and Bacillus velezensis) Isolated from Arabian Sea Seamount Sediments for Plant Growth Promotion.

Arabian Sea is a highly productive Ocean owing to deep upwelling with reports on phosphorus cycling in ocean sediments. In this study, microbes from sea mounts of the Arabian Sea at varying depths (400m, 900m) were screened to isolate and characterize phosphate-solubilizing bacteria (PSB) with plant growth-promoting properties. Out of the seven morphologically different PSBs, two bacterial strains with maximum phosphate solubilization index were identified as Priestia megaterium (H1) and Bacillus velezensis (H2) based on biochemical and molecular characteristics. Different factors influencing phosphatase production were optimized, which showed maximum solubilization at temperature of 30°C (97.5μg/mL), glucose as best carbon source (70µg/mL), 1-M NaCl (114.1µg/mL), and pH 8 (134.3µg/mL) indicating their halophilic and alkaliphilic characteristics. Alkaline phosphatase enzyme was extracted and partially purified from both PSBs wherein H2 strains showed greater specific activity (24.83 U/mg). Metabolomics studies through HPLC revealed maximum production of gluconic acid (483.75mg/L) in addition to lactic, oxalic, acetic, and succinic acid during solubilization. Biopriming effect of PSBs on tomato seed germination showed high germination index (80%) in consortia of both isolates which was also validated through root colonization by SEM analysis. Further studies using pot assay experiments also showed comparable results in marine PSB consortia with positive control (Phosphobacteria) for plant growth attributes including root height and weight. These findings suggest that the halophilic PSB strains from marine sediments could be used as potential bio-inoculants to enhance plant growth and combat saline stress for sustainable Agriculture.

The role of proton excreted by Advenella kashmirensis DF12 during ammonium assimilation in phosphate solubilization.

Phosphate-solubilizing bacteria (PSB) can solubilize soil fixed phosphorus (P) to plant available forms. In previous studies, the mechanisms of inorganic phosphate solubilization by PSB mostly focused on the acidolysis of organic acids. Here we screened a highly efficient PSB, Advenella kashmirensis DF12, with the maximum P solubilization of 590 mg L- 1 at 6 days. In addition to its P solubilizing ability, DF12 also showed a tolerance to pH from 5 to 10 and a nitrogen fixation potential. The multiple functions of DF12 and its wide adaptability to various environmental conditions make it a promising biofertilizer candidate. The combined analysis of extracellular metabolites and intracellular metabolome data revealed that the production of organic acid (mainly gluconic acid) is not the only mechanism of P solubilized by DF12, the solubilized P content was not correlated with the gluconic acid concentration but was in a highly significant positive correlation with proton concentration, extrusion of proton during NH4+ assimilation plays a key role in phosphate solubilization. Moreover, the contribution of NH4+ assimilation to phosphorus solubilization is generally present in PSB. Therefore, we proposed that applying ammonium fertilizer in P-deficient soil is more appropriate, it can not only supplement nitrogen fertilizer, but also enhance P use efficiency, which contributes to worldwide fertilizer use reduction and efficiency improvement.

Response of Biofertilizer and Molybdenum on Growth and Yield of Barley (Hordeum vulgare L.)

The field experiment was conducted during rabi season, 2023-24 at research farm, Vivekananda Global University, Jaipur. The experiment was layout in Randomized Block Design (RBD). The treatments consisted of biofertilizers like Azotobacter and Phosphate Solubilizing Bacteria (PSB) and three level of Molybdenum (400, 600 and 800 ppm) and control. The soil in the experimental area was sandy loam with pH (7.81), Organic Carbon (0.21%), Available N (132.5 kg/ha), Available P (21.13 kg/ha) and Available K (203.24 kg/ha). Seed rate is 100 kg/ha. The application of biofertilizers + PSB + 800 ppm Mo significantly increased the Plant height (110.46 cm), Dry matter accumulation (542.54 g/m2), No. of tillers/ running row meter (93.51), Number of effective tillers m-2 (199.86), Number of grains spike-1 (53.60), Grain yield (3450 kg/ha) and Straw Yield (6562 kg/ha) of barley over the control.

Effects of phosphate-solubilizing bacteria Aspergillus flavus AF-LRH1 on promoting phosphorus solubilization, wheat growth and soil heavy metal remediation

Increasing nutrient supply level and eliminating pollution risk are essential to promote farmland soil use. In the soil-plant nutrition cycle, phosphorus is a limiting nutrient, toxic metals such as Cd and Pb are stress threats. Utilizing microorganisms as a bio-amendment could be a viable approach to enhance the cycling of soil phosphorus nutrients and immobilize Cd and Pb in the soil. This study involved the isolation of Aspergillus flavus AF-LRH1, a phosphate solubilizing fungal strain from soil. The strain exhibited the capacity to solubilize calcium phosphate, attaining a phosphorus concentration of 220.73 mg L−1 in the medium. High performance liquid chromatography analysis showed that AF-LRH1 produced a combination of organic acids (tartaric acid 260.7 mg L−1, fumaric acid 0.8 mg L−1, citric acid 911.9 mg L−1) to dissolve Ca3(PO4)2 by providing H+ ions. AF-LRH1 also utilizes NH4+ for the biosynthesis of amino acids and releases protons, which facilitate the dissolution of insoluble Ca3(PO4)2 and calcium phytate. Through these processes, calcium phosphate is partly converted into hydroxyapatite because of biological solubilization. AF-LRH1 strain showed the capability to recover phosphorus from various types of sludge-based solid residue by increasing the solubility of insoluble phosphate compounds for plant nutrient supply. In addition, the combining addition of AF-LRH1 strain and phosphate-containing amendments (calcium phosphate, sludge ash and biochar) benefited the decontamination of Pb and Cd contaminated soil. This finding confirmed the AF-LRH1 could be a promising environmental-friendly biofertilizer suitable for agricultural applications and bioremediation of heavy metal contaminated soil.

Interactions between arbuscular mycorrhizal fungi and phosphate-soluble bacteria affect ginsenoside compositions by modulating the C:N:P stoichiometry in Panax ginseng.

The biomass production as well as the accumulation of secondary metabolites of plant is highly determined by the absorption of nutritional elements, in particular nitrogen (N) and phosphorus (P). Arbuscular mycorrhizal fungi (AMF) can absorb soluble P and transport it to plants, while phosphate solubilizing bacteria (PSB) can increase the content of solubilizing P in soil. Previous studies have identified the effects of either AMF or PSB inoculation on altering plant C:N:P stoichiometry, whether AMF interact with PSB in promoting plant growth and changing elemental concentration and composition of secondary metabolites by altering plant C:N:P stoichiometry remains ambiguous. In this study, we investigated the effects of inoculation of AMF, PSB, and their co-inoculation AMP (AMF and PSB) on the biomass growth, the C:N:P stoichiometry, the core microorganisms of rhizosphere soil, and the ginsenoside compositions of ginseng (Panax ginseng). The results showed that compared to control or single inoculation of AMF or PSB, co-inoculation of AMF and PSB significantly increased the AMF colonization rate on ginseng roots, increased the biomass of both above and under-ground parts of ginseng. Similarly, co-inoculation of AMF and PSB substantially increased the concentrations of N and P, reduced the ratios of C:P and N:P in the above-ground part of ginseng. The co-inoculation of AMF and PSB also increased concentrations of total ginsenosides and altered the compositions of ginsenosides in both the above and under-ground parts of ginseng. Analysis the rhizosphere microorganism showed that the co-inoculation of AMF and PSB recruited distinct core microorganisms that differ from the control and treatments with single inoculation of AMF or PSB. Our results suggested that PSB inoculation enhanced the positive effect of AMF in improving the absorption of nutrimental elements, altered the C:N:P stoichiometry and, ginsenosides concentration and composition of ginseng, influenced the plant rhizosphere microbial community. These findings offer valuable insights into enhancing plant biomass production and promoting secondary metabolites by improving the plant-fungi-bacterial relationships.

Effects of calcium phosphate and phosphorus-dissolving bacteria on microbial structure and function during Torreya Grandis branch waste composting

Background Burkholderiais a phosphorus solubilizing microorganism discovered in recent years, which can dissolve insoluble phosphorus compounds into soluble phosphorus. To investigate the effects of Burkholderia and calcium phosphate on the composting of Torreya grandis branches and leaves, as well as to explain the nutritional and metabolic markers related to the composting process.MethodsIn this study, we employed amplicon sequencing and untargeted metabolomics analysis to examine the interplay among phosphorus (P) components, microbial communities, and metabolites during T. grandis branch and leaf waste composting that underwent treatment with calcium phosphate and phosphate-solubilizing bacteria (Burkholderia). There were four composting treatments, 10% calcium phosphate (CaP) or 5 ml/kg (1 × 108/ml Burkholderia) microbial inoculum (WJP) or both (CaP + WJP), and the control group (CK).ResultsThe results indicated that Burkholderia inoculation and calcium phosphate treatment affected the phosphorus composition, pH, EC, and nitrogen content. Furthermore, these treatments significantly affected the diversity and structure of bacterial and fungal communities, altering microbial and metabolite interactions. The differential metabolites associated with lipids and organic acids and derivatives treated with calcium phosphate treatment are twice as high as those treated with Burkholderia in both 21d and 42d. The results suggest that calcium phosphate treatment alters the formation of some biological macromolecules.ConclusionBoth Burkholderia inoculation and calcium phosphate treatment affected the phosphorus composition, nitrogen content and metabolites of T. grandis branch and leaf waste compost.These results extend our comprehension of the coupling of matter transformation and community succession in composting with the addition of calcium phosphate and phosphate-solubilizing bacteria.

Enhanced phosphorus availability and cadmium remediation using phosphate-solubilizing bacteria-loaded biochar in contaminated soils

Phosphate-solubilizing bacteria (PSB) have garnered extensive attention for their ability to improve soil phosphorus (P) availability and their potential applications in bioremediation. However, the efficacy of PSB is contingent upon their colonization in soils, which can be hindered by the toxicity of heavy metals such as cadmium (Cd). Utilizing biochar as a protective carrier for PSB presents a promising strategy to address this challenge. This study investigated the effects of PSB-loaded biochar on soil P pools and wheat (Triticum aestivum L.) growth under Cd-contaminated conditions. Results indicated that biochar loading facilitated the colonization and functioning of the inoculated PSB strain (Bacillus subtilis), as evidenced by increased soil cultivatable PSB abundance and phosphatase activity as well as increased relative abundance of Bacillus in bacterial community. Consequently, improved soil P availability and reduced soil exchangeable Cd content were observed, leading to a 30.3% increase in wheat shoot biomass, a 50.4% increase in P accumulation, and a 24.1% reduction in Cd accumulation in wheat shoots under the PSB-loaded biochar treatment. Significant shifts in bacterial community composition were revealed by 16S rRNA amplicon sequencing and enhanced microbe-mediated metabolic activities were observed, as demonstrated by soil enzyme assays and metabolome analysis. Overall, these findings underscore the potential of PSB-loaded biochar to enhance P availability, mitigate Cd toxicity, and shape the soil microbial community, offering a promising strategy for sustainable nutrient management and bioremediation in Cd-contaminated agricultural soils.

Determining the Effect of Integrated Nutrient Management (INM) on the Growth of Tuberose (Polianthes tuberosa L.) cv. Rajat Rekha

Tuberose, a valuable ornamental crop, requires optimized nutrient management to maximize its potential. With increasing concerns about chemical fertilizer usage, integrated nutrient management (INM) offers a sustainable alternative. This study investigated the effects of INM on Tuberose (Polianthes tuberosa L.) cv. Rajat Rekha, exploring combinations of organic and inorganic fertilizers to promote growth and productivity. The results showed that integrated nutrient management significantly enhanced growth parameters. Specifically, the treatment combining 75% Recommended Dose of Fertilizer (RDF) with 2 kg Farm Yard Manure (FYM)/m2, 300g Vermicompost (VC)/m2, Phosphate Solubilizing Bacteria (PSB), and Azospirillum (T15) yielded superior results. This treatment reduced days to sprouting (12.10 and 14.18), and improved plant height (40.8 and 41.7 cm), leaf length (48.0 and 48.6 cm), leaf width (1.78 and 1.80 cm), and leaf number (60.8 and 61.4). These findings suggest that integrated nutrient management can enhance Tuberose productivity while minimizing chemical fertilizer reliance. The identified optimal treatment combination offers a viable strategy for sustainable Tuberose cultivation, contributing to environmentally friendly agricultural practices. Future research can focus on scaling up these results and exploring potential applications in other ornamental crops.

Enhancing phosphorus availability and growth of green gram (Vigna radiata) in acidic red and laterite soil through liquid formulations of native phosphate solubilizing bacteria

Phosphorus (P) availability in acid soils is often limited due to its fixation with various soil components. This leads to low use efficiency of P fertilizers and raises environmental concerns when they are used in excess. Phosphate-solubilizing bacteria (PSB) have the potential to enhance P availability by solubilizing insoluble P forms. In this study, twenty-five PSB strains were initially isolated from acidic red and laterite soils in eastern India. Among them, ten bacteria formed a clear halo zone in Pikovskaya agar plates. The P releasing ability of these bacteria from different insoluble P sources was evaluated. The PSB strain AJ14, identified as Enterobacter sp., exhibited high P releasing capacity from tri-calcium phosphate, rock phosphate, ferric phosphate, and aluminum phosphate. Additionally, the strain demonstrated the ability to release zinc and potassium from insoluble sources. To improve the shelf life and efficacy of the PSB strain, liquid biofertilizer formulations were developed using polymeric additives such as polyvinylpyrrolidone, polyethylene glycol, glycerol, carboxymethyl cellulose, and tween 20. The liquid formulations showed enhanced survival and viability of the PSB strain compared to solid carrier-based biofertilizers. In a pot culture experiment with green gram plants, the liquid formulations significantly increased soil available P, dry matter yield, and P uptake by plants compared to the control and solid carrier-based biofertilizer treatment. Mitscherlich equation parameters indicated the greater effectiveness of the liquid formulations. The results suggest that liquid formulations of the PSB strain AJ14 can improve P utilization efficiency and plant growth in acidic red and laterite soils.