Phosphate Solubilization Potential Research Articles

Effect of different phosphate sources on uranium biomineralization by the Microbacterium sp. Be9 strain: A multidisciplinary approach study.

Industrial activities related with the uranium industry are known to generate hazardous waste which must be managed adequately. Amongst the remediation activities available, eco-friendly strategies based on microbial activity have been investigated in depth in the last decades and biomineralization-based methods, mediated by microbial enzymes (e.g., phosphatase), have been proposed as a promising approach. However, the presence of different forms of phosphates in these environments plays a complicated role which must be thoroughly unraveled to optimize results when applying this remediation process. In this study, we have looked at the effect of different phosphate sources on the uranium (U) biomineralization process mediated by Microbacterium sp. Be9, a bacterial strain previously isolated from U mill tailings. We applied a multidisciplinary approach (cell surface characterization, phosphatase activity, inorganic phosphate release, cell viability, microscopy, etc.). It was clear that the U removal ability and related U interaction mechanisms by the strain depend on the type of phosphate substrate. In the absence of exogenous phosphate substrate, the cells interact with U through U phosphate biomineralization with a 98% removal of U within the first 48 h. However, the U solubilization process was the main U interaction mechanism of the cells in the presence of inorganic phosphate, demonstrating the phosphate solubilizing potential of the strain. These findings show the biotechnological use of this strain in the bioremediation of U as a function of phosphate substrate: U biomineralization (in a phosphate free system) and indirectly through the solubilization of orthophosphate from phosphate (P) containing waste products needed for U precipitation.

Penicillium oxalicum augments soil lead immobilization by affecting indigenous microbial community structure and inorganic phosphate solubilization potential during microbial-induced phosphate precipitation

Phosphate-solubilizing microorganisms (PSMs) are critically important for increasing soil phosphate (P) and decreasing lead (Pb) bioavailability during microbial-induced phosphate precipitation (MIPP). However, their relative contributions to the indigenous soil microbial communities and P-cycling genes during the MIPP process remain unclear. In this study, inoculation of the PSM P. oxalicum in hydroxyapatite-cultured and Pb-contaminated soil increased soil phosphatase activities, available P (AP) concentrations and reduced available Pb levels. Metagenomics revealed a 3.9–44.0% increase in the abundance of P-cycling genes by P. oxalicum inoculation. No P-cycling genes were assigned to Penicillium. While P. oxalicum increased the complexity of microbial community co-occurrence networks, and improved the directly interrelationships between Penicillium and genera containing P-cycling gene. These results suggesting that P. oxalicum obviously positively affected the regulation of indigenous P-cycling functional communities during the MIPP process. Inorganic P solubilization genes (gcd, ppa, and ppx) have been shown to affect soil AP, suggesting that inorganic P solubilization is the major driver of Pb immobilization improvement following P. oxalicum inoculation. These results enhance our understanding of the significant ecological role of PSMs in governing soil P-cycling and alleviating Pb2+ biotoxicity during the MIPP process.

Impact Assessment of Varied Agroclimatic Conditions on Phosphate Solubilization Potential of Fungi in Fermentation and Soil-Plant System

In this work, two phosphate solubilizing fungi viz., Aspergillus tubingensis S33 and A. niger S36 were studied under different physiochemical and nutritional parameters in the lab, and in vitro under soil-plant experiments at two very distinct agro-climatic conditions viz., Banasthali, Tonk (Rajasthan), and Dwarahat, Almora (Uttarakhand), India. Phosphate-solubilizing capability was checked with different carbon and nitrogen sources. Maltose, glucose, and fructose were optimal carbon source in A. tubingensis S33 while fructose in the case of A. awamori S33. Amongst nitrogen sources, S33 showed maximum phosphate solubilization with ammonium sulfate while, S36 with ammonium sulfate and sodium nitrate. Ammonium was more stimulating than nitrate as the chief nitrogen source. In vivo experiments revealed that solubilization was noticeable at all the temperatures, but optimal temperature was 25–35℃. The optimal initial pH for Tricalcium Phosphate (TCP) solubilization was 8.0. The ideal concentration of TCP for solubilization was 7.5 g∙l−1. The application of both strains in two different geographical sites exhibited a significant (p<0.05) rise in wheat growth, grain yield, and available Phosphorus (P). Fungal inoculation with TCP amendment exhibited a more notable effect on growth, yield, and soil fertility than control. This study support that these isolates will be able to work efficiently in varied climatic conditions and will show consistent efficiency on field application.

Phytohormones producing rhizobacteria alleviate heavy metals stress in soybean through multilayered response

Aimof the current research was to use plant growth promoting rhizobacteria for sequestration and biotransformation of the toxic form of Cr and As into non-toxic form. Remediating these contaminants using microbes is a common technique and rhizo-microbiota not only relieves metal stress but also acts as biofertilizers. Role of plant growth-promoting rhizobacterial (PGPR) strains Acinetobacter beijerinckii (C5) and Raoultella planticola (C9) in counteracting chromium and arsenic stress in soybean seedlings was assessed. The isolated rhizobacteria were able to tolerate excessive quantities (up to 1200 ppm) of chromate and arsenate in liquid media. Beside their growth in heavy metal containing media, the strains were able to bio-transform chromate and arsenate to their least toxic form. They released significant quantities of stress related metabolites including phenols, flavonoids, proline, sugars and protein even in the presence of 1200 ppm of the heavy metals. They also released several plant hormones together with indole-3-acetic acid (IAA), salicylic acid (SA) and gibberellins. Another important feature of the isolates was their ability to solubilize phosphate and release siderophores and exposure to different levels of the selected heavy metals enhanced phosphate solubilization potential of both the isolates by up to 2-fold. Release of siderophore in A. beijerinckii C5 was enhanced by increasing heavy metals concentration in the media but in case of R. planticola C9 a decline was noted. When inoculated on soybean seedlings, the isolates modulated several metabolites of the hos plant enabling them to combat heavy metal toxicity at different levels. The PGPR strains boosted host’s antioxidants production which minimized the oxidative damage by scavenging excessive ROS produced under stress. Control plants showed upregulation of stress response metabolites compared to PGPR application, whereas, IAA and SA were significantly higher in PGPR associated seedlings. In conclusion, PGPR alters the physiological and metabolic responses of soybean enabling it to cope better with chromate and arsenic toxicity and grow well under the stress.

Bioconversion of Some Agro-Residues into Organic Acids by Cellulolytic Rock-Phosphate-Solubilizing Aspergillus japonicus

Biological-based conversion of agricultural residues into bioactive compounds may be considered to be the basis for various vital industries. However, finding a suitable microorganism is a challenge in the bioconversion process. Therefore, this study was conducted to find local fungal isolates able to convert a combination of plant biomass residues into organic acids (OAs). Based on their cellulase and phytase activities and rock phosphate (RP) solubilization potential, an efficient 15 fungal isolates (named F1 to F15) were selected and identified by both morphological and molecular methods using the 18S rRNA sequencing technique. The best fungal isolate (F15) was identified as Aspergillus japonicus. After 4 weeks of incubation below solid-state fermentation (SSF) with a mix of sugarcane bagasse and faba bean straw (3:7), with 7.5% (v/w) fungal inoculum to the growth medium, the biodegradation process by the fungus reached its peak, i.e., maximum cellulolytic activity and RP solubilization ability. Under such fermentation conditions, seven organic acids were detected using HPLC, in the following order: ascorbic acid &gt; oxalic acid &gt; formic acid &gt; malic acid &gt; succinic acid &gt; lactic acid &gt; citric acid. Based on the results, Aspergillus japonicus (F15) could produce OAs and cellulose enzymes, and could be considered a new single-step bio-converter of sugarcane bagasse and faba bean straw residues into OAs. Furthermore, this fungus could be a new source of fungal cellulose, and could present a practical approach to reducing environmental contamination. Additional work is encouraged for more optimization of fermentation conditions.

Designing an Efficient Consortium for Improved Crop Productivity using Phosphate Stress Adapted Bacteria with Multiple Growth-Promoting Attributes

An efficient consortium NEER-PHOS was designed using high phosphate solubilizing microbes isolated from lab-scale bioreactor operated under phosphate (Pi) rich, limiting, and stress conditions to meet the current agronomy demands in an eco-friendly manner. Individual microbes were screened for higher phosphate solubilizing potential with additional growth-promoting abilities like nitrogen fixation, potassium solubilization, auxin, and HCN production. The best-selected multipotent microbes were used to design the consortium. The selected microbes T166, X225, X303, X308, X298, and PVN-1 were identified as Proteus mirabilis, Pseudomonas sp., Pseudomonas aeruginosa, Chryseobacterium sp., and Klebsiella pneumoniae, respectively and results into more than 250 mg/L released PO4 3 in liquid medium. A total of 63 consortium combinations were assayed, and the best solubilizing combination, number 58 (557.8 mg/L-PO4 3−), was selected for the pot experiment. The performance of the designed consortium was studied on Vigna radiata, Cicer arietinum, and Triticum aestivum. The overall analyzed growth parameters suggest that the designed consortium enhances growth significantly (p < 0.05) and reduces fertilizers by 50–100% in V. radiata and C. arietinum. Hence, the designed consortium NEER-PHOS can reduce the chemical fertilizer application and simultaneously improve plant productivity.

ACC Deaminase Containing Plant Growth Promoting Agrobacterium larrymoorie Strain MZ 3-ABF Confers Tolerance to Drought Stress in Chickpea (Cicer arietinum L.) Seedlings

Plant growth-promoting rhizobacteria (PGPR) that produce 1-aminocyclopropane-1-carboxylate (ACC) deaminase can alleviate plant growth constraints caused by water scarcity. In the present study, six PGPR strains were evaluated to produce several plant growth promoting, and ACC deaminase enzyme isolated from the rhizosphere soil of Chickpea (Cicer arietinum) in arid regions of Telangana State, India. According to their 16S rDNA sequencing analysis, only one of the six strains, MZ 3-ABF, belongs to Agrobacterium larrymoorie. A drought tolerance experiment revealed two PGPR strains with high phosphate solubilization, nitrogen fixation, indoleacetic-3-acid (IAA), and ACC deaminase enzyme secretion potential were constrained to only MZ 3-ABF and MZ 5-ABF. One strain MZ 3-ABF was chosen for use in a pot experiment to assess their growth-promoting effects on chickpea under drought conditions. This PGPR strain inoculation into chickpea seedlings was expected to alleviate the overall growth inhibition caused by drought stress. The inoculation was thought to have the greatest growth-promoting effects. Inoculation with strain MZ 3-ABF altered plant height, root length, dry biomass, and net photosynthetic rate of leaves, allowing chickpea seedlings to cope with drought better. They had an indirect effect on the biochemical and physiological properties of chickpea seedlings in order to alleviate drought stress. These findings suggest that the MZ 3-ABF PGPR may be useful for effectively weakening the growth inhibition caused by drought in chickpea. The strain could also be used as effective bioinoculant to maintain pea quality.

Characterization and identification of plant growth promoting endophytic bacterial strain IU10

Growing evidence has suggested that plant growth-promoting endophytic bacteria can regulate, which can be used as biofertilizers, bio-stimulants, and biocontrol agent. In the present study, Bacillus subtills IU10 was isolated from plants and was subjected to advanced chromatography and spectroscopic techniques for the extraction and isolation of indole-3-acetic acid (IAA). Up to 10 ?g/mL of IAA was quantified in the bacterial extract using the [2H2]-IAA internal standards in GC-MS analysis. PVK agar containing Ca3(PO4)2 was used to measure the ability of IU10 to solubilize phosphate. The clear zones formed by phosphate solubilization were measured to assess the phosphate solubilization potential. Azurol-S (CAS) medium was used for measuring siderophore production. The orange halo circles were measured to quantify the siderophore production. Endophytic IU10 inoculated plants showed significantly improvement root to shoot length, biomass and chlorophyll as compared to control. The data indicates that IU10 produce phytohormones, siderophore and immobilize nutrients could be used as biofertilizer. Keywords: phytohormones, nutrient immobilization, growth promotion, endophytes.

Bacillus subtilis suppresses the charcoal rot disease by inducing defence responses and physiological attributes in soybean.

Endophytes can induce the defence responses and modulates physiological attributes in host plants during pathogen attacks. In the present study, 127 bacterial endophytes (BEs) were isolated from different parts of healthy soybean plant. Among them, two BEs (M-2 and M-4) resulted a significant antagonistic property against Macrophomina phaseolina, causes charcoal rot disease in soybean. The antagonistic potential was evaluated through dual culture plate assay, where M-4 expressed higher antifungal activity than M-2 against M. phaseolina. The M-4 produces cell wall degrading enzymes viz. cellulase (145.71 ± 1.34 μgmL-1), chitinase (0.168 ± 0.0009 unitmL-1) and β,1-3 endoglucanase (162.14 ± 2.5 μgmL-1), which helps in cell wall disintegration of pathogens. Additionally, M-4 also can produce siderophores, indole-3-acetic acid (IAA) (17.03 ± 1.10 μgmL-1) and had a phosphate solubilization potential (19.89 ± 0.26 μgmL-1). Further, GC-MS profiling of M-4 has been carried out to demonstrate the production of lipophilic secondary metabolites which efficiently suppress the M. phaseolina defensive compounds under co-culture conditions. Bio-efficacy study of M-4 strain shown a significant reduction in disease incidence around 60 and 80% in resistant and susceptible varieties of soybean, respectively. The inoculation of M-4 potentially enhances the physiological attributes and triggers various defence responsive enzymes viz. superoxide dismutase (SOD), phenol peroxidase (PPO), peroxidase (PO) and catalase (CAT). The histopathological study also confirmed that M-4 can reduce the persistence of microsclerotia in root and shoot tissue. Conclusively, M-4 revealed as an efficient biocontrol agent that can uses multifaceted measures for charcoal rot disease management, by suppress the M. phaseolina infection and enhance the physiological attributes of soybean.

Genetic Diversity and Characterization of Plant Growth-Promoting Effects of Bacteria Isolated from Rhizospheric Soils

Plant growth-promoting rhizobacteria (PGPR) have the potential to make a significant contribution to the development of sustainable agricultural systems. Generally, PGPRs function in three different ways, summarized as the synthesis of certain compounds for plants, facilitating the uptake of certain nutrients from the soil and protecting plants from diseases. This study aims to isolate plant growth-promoting bacteria from different plant rhizospheres from Ankara province, to reveal their genetic diversity, and to determine their plant growth-promoting properties. The identification of the 69 isolates was made according to the 16S rDNA sequence results and ARDRA analyses were also performed using AluI, HeaIII, and MspI enzymes. Nitrogen fixation, phosphate dissolving, IAA (indole-3-acetic acid) and siderophore production capacities of the 69 bacterial strains including 12 different genera (30 Pseudomonas, 13 Arthrobacter, 7 Bacillus, 4 Phyllobacter, 4 Variovorax, 3 Olivibacter, 3 Enterobacter, 2 Paenarthrobacter, 1 Stenotrophomonas, 1 Flavobacterium, 1 Caulobacter, 1 Paenibacillus) were evaluated in in vitro conditions. Nitrogen fixation capacities of 55 isolates varied between 2.29 and 46.11µgmL-1 according to micro-kjeldahl method. Among the strains studied, nifH gene was detected only in Paenibacillus polymyxa H8/2 strain. The highestPhosphorus dissolving and IAA production capacity (in tryptophan-added medium) of isolates were 186.52µgmL-1, and50.05μgmL-1 respectively, and 31 of 69 isolates were able to produce siderophore. Regarding antifungal activities, results showed that 31 bacterial isolates had antagonistic activities against at least one of the tested pathogens. Nitrogen fixation and phosphate solubilizing potential of the promising bacterial strains were determined through two-independent pot experiments with wheat and it has been found that they have positive effects on the yield parameters of wheat.

Minjingu phosphate rock solubilization and potential for use of Klebsiella variicola-MdE4 and Klebsiella variicola-MdG1 as biofertilizer for maize production

Limited solubility of the Tanzania’s Minjingu phosphate rock (MPR) in non-acidic soil conditions has held back its potential for widespread use in agricultural production. This study was designed to isolate, characterize and test phosphate-solubilizing bacteria for their potential to increase solubility of MPR and enhance maize plant growth under field conditions. Ten out of 19 isolates showing greatest phosphate solubilization indices on a Pikovskaya agar medium were further characterized for other plant-growth promoting traits including production of IAA, siderophores and ammonia. Two of them, namely isolates-MdE4 and MdG1 substantially outperformed other isolates in phosphate solubilization and production of IAA, ammonia and siderophores. The two isolates molecularly identified as Klebsiella variicola-MdE4 and K. variicola-MdG1 produced up 701, 699 and 750, 680 μg/ml of soluble phosphate from tricalcium phosphate and hard Minjungu rock phosphate, respectively. Additionally, Biorock P- a biofertilizer formulation containing MdE4 and MdG1 co-cultured in a molasses-based modified broth medium retained most of the phosphate solubilizing potential and other plant-growth promoting traits of MdE4 and MdG1. Co-application of MdE1 and MdG1-containing “bio-rock P” and inorganic phosphate at 20 kg P/ha resulted in higher maize grain yield than that of positive control (40 kg P/ha) under field conditions. The two isolates- Klebsiella variicola-MdE4 and K. variicola-MdG1 have the potential for use in a biofertilizer formulation for commercial field applications.

Inorganic and organic phosphate solubilization potential of Stenotrophomonas maltophilia

Most soils contain Phosphorus (P) in insoluble compounds as organic and inorganic forms which is unavailable to plants. Furthermore, phosphate solubilizing bacteria (PSB) play an important role in converting insoluble P to a bioavailable form through solubilizing and mineralizing inorganic or organic P. Therefore, this study aims to determine the ability of isolate a phosphate solubilizing bacterium (PSB), Stenotrophomonas maltophilia to solubilize inorganic and organic P. The bacterium was isolated from peat soil of West Kalimantan using Pikovskaya medium added with Ca3 (PO4)2 as the P source. The activity of organic P (acid phosphatase and phytase) was measured using p-nitrophenyl phosphate disodium (pNPP 0.115 M) and sodium phytate as the substrate of bacterial broth culture. Also, the optimization for inorganic and organic P solubilization by the bacterium was conducted. The maximum values of inorganic and organic phosphate solubilization was recorded to be 52.26 μg/mL and 44.51 U/mL (acid phosphatase), 0.13 U/mL (phytase) respectively. Optimum conditions found were temperature at 30 °C, pH 6.0 and in the presence of sucrose and beef extract, which serve as carbon and nitrogen sources, respectively. Therefore, it can probably be used as a biological fertilizer for plants.

Effect of Native Trichoderma asperellum Isolate on Phosphate Solubilization and Growth of Pea

Application of phosphorus solubilizing microbes is a promising tool for enhancing P uptake in plant. The aim of this study was to evaluate the phosphate solubilization potential and growth promotion of pea (Pisum sativum L.) by native Trichoderma asperellum isolate G3. Phosphate solubilization by T. asperellum strain was assessed in National Botanical Research Institute’s Phosphate (NBRIP) broth medium. Pea plants were inoculated by Trichoderma strain and grown in pot in phosphate deficit condition. The fungal strain was able to solubilize phosphate (from 188.95±2.04 to 262.50±3.80 mgL-1) in broth at different time periods and decreased solution pH. The Trichoderma inoculated pea plant increased the root growth, shoot growth, leaf number, shoot biomass, root biomass, total dry weight, chlorophyll a, chlorophyll b and carotenoid by 23.9%, 33.3%, 33%, 37.1%, 32.7%, 28.4%, 24.5%, 17.4% and 14.7% respectively over control after 5 weeks of post inoculation. The results showed that the native T. asperellum isolate G3 has great potential in the phosphorus solubilization. Ann. Bangladesh Agric. (2020) 24(2) : 121-124

Isolation, Identification and Characterization of Phosphate Solubilizing Bacteria from Jhum Field of Mizoram, India

Phosphorus (P) is one of the most important nutrients and its low availability in soil is a limiting factor for the growth and development of plants. In jhum cultivation, there is considerable loss of soil nutrients especially phosphorous (P). Since soil P are an important soil nutrient, the use of native phosphate solubilizing bacteria (PSB) capable of converting the insoluble P to soluble form can serve as biofertilizers to increase the amount of plant-available P. PSB native to jhum and jhum fallow soil were isolated and screened for their phosphatase enzyme and indole compound production. These bacteria are being explored for development as biofertilizers to increase crop production in jhum cultivation as well as faster eco-restoration of jhum fallow. Base on their ability of solubilizing tri-calcium phosphate in Pikovskaya agar medium, a total of 44 PSBs were isolated from the current jhum field and different age fallow. Molecular characterization of 44 bacterial showing phosphate solubilization potential was carried out and a phylogenetic tree was constructed. All isolates showed production of acid phosphatase enzyme and indole-like compounds. Bacterial isolates MZUR22 and MZUR37 were evaluated for their efficacy to alleviate the early growth performance of rice in vitro conditions. The in vitro assessment showed that rice plants treated with PSB isolates showed a positively significant growth performance against other treatments.

1-Aminocyclopropane-1-Carboxylate Deaminase-Producing Plant Growth-Promoting Rhizobacteria Improve Drought Stress Tolerance in Grapevine (Vitis vinifera L.).

Plant growth-promoting rhizobacteria (PGPRs) that produce 1-aminocyclopropane-1-carboxylate (ACC) deaminase are capable of reducing limits to plant growth due to water-deficient conditions. Here, seven PGPR strains that can produce ACC deaminase were successfully obtained from the rhizosphere soil of grapevine (Vitis vinifera L.) in arid regions of China. The strains belonged to three different genera: Pseudomonas, Enterobacter, and Achromobacter, according to their 16S rDNA sequencing analysis. A drought tolerance experiment revealed two PGPR strains (DR3 and DR6) with exceptionally high phosphate solubilization, nitrogen fixation, indoleacetic acid (IAA), and exopolysaccharides secretion potential. Both strains were selected for use in a pot experiment to evaluate their growth-promoting effects on grapevines under drought conditions. Each of these two PGPRs and their mixed inoculation into grapevines were expected to alleviate the comprehensive growth inhibition of grapevines caused by drought stress. The mixed inoculation was hypothesized to elicit the best growth-promoting effects. Inoculation with the PGPRs not only enhanced the root-adhering soil/root tissue ratios and soil aggregate stability, but it also increased the nitrogen and phosphorus levels in the soil and plant leaves. Further, inoculation with PGPRs significantly altered the plant height, biomass of shoot and root organs, relative water contents, and net photosynthetic rate of leaves, enabling grapevines to better cope with drought. Moreover, the contents of IAA, abscisic acid, and malondialdehyde in these grapevines under drought stress were significantly changed by PGPRs. They indirectly affected biochemical and physiological properties of grapevines to alleviate their drought stress. Taken together, these results demonstrate that the DR3 and DR6 PGPRs might be useful for effectively weakening the growth inhibition caused by drought in grapevines. The strains might also be applied as effective bioinoculants to maintain the quality of wine grapes.

Potential of Halophilic/Halotolerant Bacteria in Enhancing Plant Growth Under Salt Stress

In the current study, fourteen bacterial strains were obtained in salt contaminated soils. The identification and characterization of the bacterial strains were performed by conventional and molecular techniques. According to the results of 16S rRNA gene sequence analysis, five genera (Bacillus, Staphylococcus, Oceanobacillus, Exiguobacterium, and Halobacillus) were identified with a homology of equal to 99% or higher similarity. Afterward, these fourteen halotolerant/halophilic bacterial strains were investigated for their plant growth promoting (PGP) traits including production of indole-3-acetic acid (IAA) and siderophore, activity of 1-aminocyclopropane-1-carboxylate (ACC) deaminase, fixation of nitrogen, and phosphate solubilization potential. Five of the bacterial strains possessing PGP traits were tested for their effects on the growth of a salt sensitive plant (wheat) in a hydroponic system under salt stress (200mM). Inoculation of five bacterial strains under salt stress significantly enhanced plant weight (Triticum aestivum) ranged from 71.18 to 89.04%. Salt stress amelioration potential of Oceanobacillus picturae and Staphylococcus succinus on T. aestivum has been shown for the first time in this study. In non-saline soil, the promising effect of plant growth bacteria is clear; however, in saline soil, the use of PGP halophilic and halotolerant bacteria can increase the productivity of salt sensitive plants. Therefore, the novel halophilic and halotolerant bacteria that promote plant growth can be developed for agricultural uses in saline soils.

Isolation of endophytic bacteria from some weeds collected from a coastal site of Bangladesh and their in vitro efficacy on phosphate solubilisation and growth promotion of wheat (Triticum aestivum)

The present study investigated the phosphate solubilizing potential and in vitro plant growth-enhancing capability of five bacterial isolates of Pseudomonas sp. isolated from the endophytic region of three different weeds namely Cyperus rotundus, Amaranthus spinosus, Scirpus mucronatus which were collected from the coastal region of Bangladesh. The bacterial species were identified as Pseudomonas sp. based on their morphological characteristics. For further confirmation, molecular characterization will be done. The isolates of Pseudomonas sp. showed varying degrees of phosphate solubilizing potential on Pikovskaya's media. The results showed that isolate EnAgM3 had the utmost capability of phosphate solubilization with the competency of (77.43±0.65 %) and the second place was occupied by the isolate EnAgM2 with their competency of (74.92±0.95%). Then the isolates were used for the assessment of their in vitro growth-promoting capability of wheat (Triticum aestivum). Isolate EnAgM3 showed the best growth promotion in respect of all the parameters studied except root fresh ounce whereas EnAgM2 also significantly enhanced all the parameters except germination percentage in comparison to control. Conclusively, this study revealed that the unexplored coastal region of Bangladesh hold potential microorganisms having phosphate solubilizing and the potential of plant growth enhancement. As far as we know, it is the first comprehensive study conducted for isolating Pseudomonas sp. as the endophytic bacteria from the coastal weeds of Bangladesh and to identify their in vitro potential of phosphate solubilization as well as plant growth enhancement of wheat

Multi-Wall Carbon Nanotubes, Metal Oxide and Hydroxy-Apatite Nanoparticles Enhanced Plant Growth Promoting Capabilities of Root Endosymbionts of Cowpea (Vigna unguiculata (L.) Walp.).

The present study was aimed to evaluate the effect of three different nanomaterials (NMs) on the growth, physiology and protein profile of the endosymbiotic bacteria isolated from the root nodules of vegetable cowpea. The alterations in growth and viability of the bacterial cells, their indole-acetic acid (IAA) and siderophore production abilities, phosphate solubilization potential and total protein content were assessed. Further, the isolates were also analyzed for changes in their exopolysaccharide (EPS) production and secretion behavior with exposure to different concentrations of the NMs. The NM supplementation of the broth improved the growth, viable cell count, IAA content, siderophore production and potential to solubilize tri-calcium phosphate (TCP) as sole phosphorus (P)-source. The NMs also improved the total protein content of the bacterial cells indicating the improved physiology and biochemistry of the treated bacterial cells. The treated cells produced significantly high EPS compared to untreated control cultures. The present investigation revealed that the NMs improved plant growth abilities of cowpea root endosymbiotic bacteria, though the impact varied across various isolates as well as NM concentrations.

Phosphate Solubilization Potential of Rhizosphere Soil Bacteria and their Possible Use as Biofertilizers

PHOSPHORUS is second only to Nitrogen as the most limiting element for plant growth. The concentration of soluble P in soil is usually very low, however, more than 80% of P becomes immobile and unavailable for plant uptake. The development of a biological alternative to chemical fertilizers is of great importance for the improvement of agriculture as well as the protection of the environment. The present study investigated thirteen efficient inorganic-phosphate solubilizing bacteria (PSB) isolated from various rhizospheric soil samples collected from El-Bekaa, Lebanon. Two isolates (Pseudomonas sp. HD and Escherichia sp. HD), exhibited the highest phosphate solubilization percentages of 76.60 and 88.21%, respectively. Application of the Plackett-Burman design resulted in phosphate solubilization efficiency of 79.08 and 93.77% for Pseudomonas sp. HD and Escherichia sp. HD, respectively. In vitro cultivation of different plants was applied to reflect the relative importance of Pseudomonas sp. HD and Escherichia sp. HD as biofertilizers on growth parameter of melon (Cucumis melo var. inodorus), horse-bean (Vicia faba), cucumber (Cucumis sativus), Armenian cucumber (Cucumis melo var. flexuosus), bean (Phaseolus vulgaris) and squash (Cucurbita pepo). The best growth parameters of the studied plants where observed where seeds were soaked in water and Ca3(PO4)2 with Pseudomonas sp. HD and Escherichia sp. HD.

Lab and Field Level Potential of Endophytic Bacteria in Managing the Dry Root Rot Disease in Black Gram Incited by Rhizoctonia bataticola (Taubenh) Butler

Background: The plant growth promotion and efficacy against phytopathogens by the endophytic bacteria are being focused now due to their ecofriendly nature. Methods: Endophytic bacteria (24 nos) isolated from the roots, stems and leaves of black gram plants collected from different locations were tested for their potential to inhibit the growth of R. bataticola under in vitro and in vivo conditions. Result: The leaf endophyte BLE 4 exhibited maximum inhibition (79.6%) of R. bataticola followed by BSE 4 (77.4%), BSE 7 (77.0%) and BLE 1 (74.0%). Among these 4 isolates tested as seed treatment and soil application, there was significant increase in dry weight (7.1 g), plant height (37.7 cm), number of branches (13.2) and number of pods (26.2) in BLE 4 treated plots. Whereas, the incidence of dry root rot and yield were insignificant. In the screening study of isolates for their phosphate solubilization potential, protease activity, siderophore and HCN production, no single isolate possessed all the properties, but siderophore production, protease activity and phosphate solubilization were found in BSE 4, BRE 3, BRE 5 and BRE 10 isolates.