• Korean Journal of Soil Science and Fertilizer
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• v.46 no.6
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• pp.494-501
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• 2013

Two phosphate solubilizing Pantoea strains (P. agglomerans and P. rodasii) were employed in elucidating their phosphate solubilizing potential under different carbon and nitrogen sources, pH, temperature and salt conditions. Plant growth promoting characteristics such as ACC deaminase activity, indole acetic acid (IAA), HCN, ammonia, and siderophore production of the two strains were assessed in vitro. Potential applicability of the strains as bio-inoculants was also evaluated in pot experiments conducted under green house conditions. Phosphate solubilization measured as the amount of phosphorous released into the medium was recorded as 810 and $788{\mu}g\;ml^{-1}$ respectively by P. agglomerans and P. rodasii. Glucose at the rate of 2% was found be the best carbon source, while $(NH_4)_2SO_4$ was the best nitrogen source for both strains. Despite a slight decrease in phosphate solubilization observed at higher temperature, pH and salt concentrations, both strains could withstand against a range of temperature ($30-35^{\circ}C$), pH (7-9) and the presence of NaCl (up to 5%) without much compromising the phosphate solubilization. Different plant growth promoting traits (ACC deaminase activity, IAA, HCN, ammonia, and siderophore production) of the strains and their ability to promote the growth of green gram seedlings indicate that both strains possess high potential to be used as bio-inoculants.

• Journal of Microbiology and Biotechnology
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• v.32 no.11
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• pp.1435-1446
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• 2022

Zinc-solubilizing bacteria can convert the insoluble form of zinc into soluble forms available to plants. This study was conducted to isolate and screen zinc-solubilizing actinobacteria from rhizosphere soils and to assess their effect on vegetable soybean growth. In total, 200 actinobacteria strains belonging to 10 genera were isolated from rhizosphere soil samples. Among these isolates, four showed zinc solubilization with solubilizing index values ranging from 3.11 to 3.78 on Bunt and Rovira agar supplemented with 0.1% zinc oxide. For the quantitative assay, in broth culture, strains CME34 and EX51 solubilized maximum available zinc contents of 529.71 and 243.58 ㎍/ml. Furthermore, indole-3-acetic acid (IAA) and ammonia were produced by these two strains, the strain CME34 produced the highest amount of IAA 4.62 ㎍/ml and the strain EX51 produced the highest amount of ammonia 361.04 ㎍/ml. In addition, the phosphate-solubilizing abilities in Pikovskaya's medium of CME34 and EX51 were 64.67 and 115.67 ㎍/ml. Based on morphological and biochemical characterization and 16S rDNA sequencing, the strains CME34 and EX51 were closely related to the genus Streptomyces. In a greenhouse experiment, single-strain inoculation of Streptomyces sp. CME34 or EX51 significantly increased the shoot length, root length, plant dry weight, number of pods per plant and number of seeds per plant of vegetable soybean plants compared to the uninoculated control. These findings facilitated the conclusion that the two Streptomyces strains have potential as zinc solubilizers and can be suggested as bioinoculants to promote the growth and yield of soybean.

• Journal of Radiation Industry
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• v.3 no.1
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• pp.39-45
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• 2009

Three mineral phosphate solubilizing (MPS) bacteria where isolated from rhizosphere soil samples of common bean and weed plants. 16S rDNA analysis indicated that the isolate P2 and P3 are closely related to Pantoea dispersa while isolate P4 is closely related to Pantoea terrae. Isolates P2 and P3 recorded $381.60{\mu}g\;ml^{-1}$ and $356.27{\mu}g\;ml^{-1}$ of tricalcium phosphate (TCP) solubilization respectively on 3 days incubation. Isolate P4 recorded the TCP solubilization of $215.85{\mu}g\;ml^{-1}$ and the pH was dropped to 4.44 on 24 h incubation. Further incubation of P4 sharply decreased the available phosphorous to $28.94{\mu}g\;ml^{-1}$ and pH level was raised to 6.32. Gamma radiation induced mutagenesis was carried out at $LD_{99}$ dose of the wild type strains. The total of 14 mutant clones with enhanced MPS activity and 4 clones with decreased activity were selected based on solubilization index (SI) and phosphate solubilization assay. Mutant P2-M1 recorded the highest P-solubilizing potential among any other wild or mutant clones by releasing $504.21{\mu}g\;ml^{-1}$ of phosphorous i.e. 35% higher than its wild type by the end of day 5. A comparative evaluation of TCP solubilization by wild type isolates of Pantoea and their mutants, led to select three MPS mutant clones such as P2-M1, P3-M2 and P3-M4 with a potential to release >$471.67{\mu}g\;ml^{-1}$ of phosphorous from TCP. These over expressing mutant clones are considered as suitable candidates for biofertilization.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.4
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• pp.249-253
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• 2014

Phosphates solubilizing bacterial strains belong to Pantoea, Burkholderia and Enterobacter were isolated and employed in assessing their solubilization ability of Ca phosphate and ER phosphate (Eppawala Rock Phosphate). Among the bacterial strains used, PSB-13 (Pantoea rodasii) showed higher Ca-phosphate solubilization ($1100{\mu}g\;ml^{-1}$) as well as rock phosphate solubilization ($168{\mu}g\;ml^{-1}$). The strain was then immobilized in agar to further assess its phosphate solubilization ability. According to the results, agar encapsulated strain solubilized 0.3%, 7.31%, 20.24%, and 20.62% more Ca-phosphate and 11.53%, 15.29%, 28.48%, 36.55% (respectively in 4 cycles) more ER-phosphate than free cells. The reuse efficiency of agar entrapped bacterial cells for Ca-phosphate and ER-phosphate solubilization was greater than that by freely suspended bacterial cells. In conclusion, immobilization could enhance the phosphate solubilization capacity of the strains and thus could be used effectively in enhancing solubilization of ER phosphate.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.4
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• pp.201-205
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• 2002

The growth conditions of Pantoea aggicmerans, a phosphate solubilizing organism, were studied In our laboratory to determine the optimal conditions. Pantoea aggionerans showed the highest growth rate at 30$\^{C}$, pH 7.0 and 2 vvm, after 50 h cultivation. A certain relationship between pH and phosphate concentration was evident when the glucose concentration in the me dium was changed. Increasing glucose concentration increased the pH buffer action of the broth. At glucose concentrations higher than the optimum concentration of 0.2 M, the cell growth was retarded. P. agglomerans consumed glucose as a substrate to produce organic acids which caused the pH decrease in the culture medium. The phosphate concentration in the medium was increased by the presence of the organic acids, which solubilized insoluble phosphates such as hydroxyapa-tite.

• Proceedings of the Korean Society of Crop Science Conference
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• 2020.06a
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• pp.31-31
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• 2020

• Korean Journal of Agricultural Science
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• v.43 no.3
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• pp.401-414
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• 2016

The synergistic effect on phosphate solubilization of single- and co-inoculation of two phosphate solubilizing bacteria, Burkholderia anthina PSB-15 and Enterobacter aerogenes PSB-16, was assessed in liquid medium and green gram plants. Co-inoculation of two strains was found to release the highest content of soluble phosphorus ($519{\mu}g\;mL^{-1}$) into the medium, followed by single inoculation of Burkholderia strain ($492{\mu}g\;mL^{-1}$) and Enterobacter strain ($483{\mu}g\;mL^{-1}$). However, there was no significant difference between single inoculation of bacterial strain and co-inoculation of two bacterial strains in terms of phosphorous release. The highest pH reduction, organic acid production, and glucose consumption were observed in the culture medium co-inoculated with PSB-15 and PSB-16 strains rather than that of single inoculation. Based on the plant growth promotion bioassay, co-inoculated mung bean seedlings recorded 9% and 8% higher shoot and root growth, respectively, compared to the control. Therefore, in conclusion, co-inoculation of the strains B. anthina and E. aerogenes displayed better performance in stimulating plant growth than inoculation of each strain alone. However, considering the short assessment period of the present study, we recommend engaging in further work under field conditions in order to test the suitability of these strains as bio-inoculants.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.5
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• pp.500-506
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• 2008

Enhanced phytoremediation with EDTA or PSM(Phosphate solubilizing microorganism) was studied using green foxtail (Setaria viridis) in columns packed with 1,200 mgPb/kg contaminated soil to investigate the effects of EDTA or PSM on the plant uptake and vertical migration of Pb. EDTA, equimolar amount of total Pb in the column soil, was administered in two methods: the one was treated with 1/6 aliquots of the equimolar EDTA every week for 6 weeks and the other was treated with single dose of the equimolar EDTA before 14 days of harvest. The results showed that higher concentrations of Pb accumulated in the biomass of green fowtail after the chemical or biological treatment. The plant-root Pb concentration in PSM treatment(M), EDTA aliquot treatment(ES), and single dose treatment(E) was 2.6, 3.0, and 3.3 times higher, respectively, than that in the plant-root of control(164.7 mg/kg). The plant-stem Pb concentration in the M, ES and E treatment was 27, 37, and 40 times higher than that in the stem of control(8.1 mg/kg). The translocation factor, the ratio of shoot/root Pb concentration, was 0.6 in the two EDTA treatment, 0.5 in the M treatment, and 0.05 in the control, respectively. The largest amount of Pb was phyto-extracted in the E treatment whereas vertical migration of EDTA was significant in the ES treatment. This result showed that a single large dose of EDTA before harvest serves better for enhanced phytoremediation of Pb. Although, treatment with PSM showed less Pb phytoextraction by the plant but enhanced both the growth of plants in the column and microbial dehydrogenase activity in the soils. Therefore, enhanced phytoextraction of Pb with PSM treatment can be an alternative option for EDTA treatment, which is toxic to plants and soil ecosystem.

• Journal of Life Science
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• v.18 no.6
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• pp.878-883
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• 2008

Aeromonas hydrophila DA33 was isolated from cultivated soils as a bacteria having high abilities to solubilize inorganic phosphate. Glucose dehydrogenase gene (gdh) was cloned from Escherichia coli. The recombinant plasmid, pGHS containing glucose dehydrogenase gene was introduced into A. hydrophila DA33 in order to improve the activity of phosphate-solubilizing. The transformant harboring the gdh gene, A. hydrophila pGHS/DA33 increased enzyme activity. The strain also increased the gluconic acid generation that was effective for phosphate solubilization. It was possible that the strain containing pGHS produced higher solubilized phosphate with tri-calcium phosphate as the unique (P) source, in comparison with that of wild type without plasmid. These results suggest that the strain, A. hydrophila pGHS/DA33 is expected as effective biofertilizer for phosphate solubilization.