Isolation Of Phosphate Solubilizing Bacteria Research Articles

Optimization of soluble phosphate and IAA production using response surface methodology and ANN approach

Phosphorus (P) is often found inaccessible to plants, as it forms precipitates with cations and can be converted to accessible forms by using Phosphate solubilizing bacteria (PSB). In the present study, isolation and characterization of PSB from rhizospheric soil of coffee plants were performed. The influence of four independent variables (incubation temperature, incubation time, pH, and inoculum size) was investigated and optimized using an artificial neural network and response surface methodology on the solubility of phosphate and indole acetic acid production. The bacterium that can dissolve phosphate were isolated in Pikovskaya's agar containing insoluble tricalcium phosphate. Total, six Phosphate Solubilizing Bacteria were isolated and three of them (PSB1, PSB3, and PSB4) were found to be effectively solubilizing phosphate. Based on phosphate solubilizing index results Pseudomonas bacteria (PSB1) was selected for modeling. The results showed that both models performed reasonably well, but properly trained artificial neural networks have the more powerful modeling capability compared to the response surface method. The optimum conditions were found to be incubation temperature of 37.5 °C, incubation time of 9 days, pH of 7.2, and inoculum size of 1.89 OD. Under these conditions, the model predicted solubility of phosphate of 260.69 μg/ml and production of IAA of 80.00 μg/ml with a desirability value of 0.947. In general, the isolated Pseudomonas is expected to have phosphorus-degrading ability that promotes plant growth, and further field experimental work is required to use this bacterial strain as biofertilizer, as an alternative to synthetic fertilizer.

Promoting growth and production of sunchoke (Helianthus tuberosus) by co-inoculation with phosphate solubilizing bacteria and arbuscular mycorrhizal fungi under drought.

Due to different functions of phosphate solubilizing bacteria (PSB) and arbuscular mycorrhizal fungi (AMF), their potential synergistic effects on enhancing plant growth and yield are worth investigating, especially under adverse conditions. This work focused on the isolation of PSB and characterization for their plant growth promoting properties under drought. The most efficient P solubilizing bacterium was isolated and identified as Burkholderia vietnamiensis strain KKUT8-1. Then, a factorial experiment on the performance of sunchoke (Helianthus tuberosus) was set up with four factors, viz., PSB (presence or absence of KKUT8-1), AMF (presence or absence of Rhizophagus aggregatus), rock phosphate (RP; added or not) and moisture (well-watered (WW) or drought (DS) conditions). Sunchoke performance was enhanced by the presence of AMF, whereas addition of PSB had a positive effect on SPAD values and inulin concentration. Drought reduced plant performance, while addition of RP reduced photosynthetic rate. There was little evidence for synergistic effects between PSB and AMF, except for SPAD values and inulin concentration. Plants that were co-inoculated with AMF and PSB had highest SPAD value, shoot diameter, leaf area, leaf number, chlorophyll concentration, plant biomass, tuber production, root growth and total soluble sugar concentration. Co-inoculated plants also had increased plant water status, reduced electrolyte leakage, and reduced malondialdehyde and proline concentration. Strain KKUT8-1 is the first strain of B. vietnamiensis capable of promoting growth and yield of sunchoke. Enhanced production of sunchoke by a combination of AMF and PSB was much better than the application of RP. Our finding offers an opportunity to develop combinations of biological inoculants for increasing the growth and production of sunchoke under drought in the future.

Phosphate solubilizing epilithic and endolithic bacteria isolated from clastic sedimentary rocks, Murree lower Himalaya, Pakistan.

Rock microbes are capable to solubilize phosphate present in the rocks.. In this study, we focused on the isolation of phosphate solubilizing bacteria from rocks of Murree, Pakistan. Both endolithic and epilithic bacteria were screened for phosphate solubilization. Three bacterial strains were selected based on halozone formation inNational Botanical Research Institute for phosphate) medium supplemented with TCP (tribasic calcium phosphate). The solubilization index for these bacteria was recorded as 4.29, 4.03 and 3.99. The pH of the medium dropped from 7.0 to 4.0 after 5days with continuous shaking at 150rpm, which facilitate the phosphate solubilization. The strains P26, P4 and N27 were identified as Pseudomonas putida strain (KT004381), Pseudomonas grimontii (KT223621) and Alcaligenes faecalis (KT004385). Strain P26 showed maximum phosphate solubilization (367.54µg/ml), while P4 and N27 showed 321.88 and 291.36µg/ml after 3days of incubation. Such inorganic phosphate solubilization could be attributed to the organic acids production by bacteria. The presence of organic acids is determined by high-performance liquid chromatography. Three different types of acids, gluconic, oxalic and malic acid were the dominant acids found in the culture medium. It may be assumed that these bacteria can play a role in weathering of rocks as well. PSB is likely to serve as an efficient biofertilizer, especially in areas deficient in P to increase the overall performance of crops.

Distribution of Culturable Phosphate-Solubilizing Bacteria in Soil Aggregates and Their Potential for Phosphorus Acquisition.

ABSTRACTDeciphering distribution patterns of phosphate-solubilizing bacteria (PSB) and phosphorus-cycling-related genes in soils is important to evaluate phosphorus (P) transformation. However, the linkage between PSB number and P-cycling-related gene abundance in soils, especially soil aggregates, remains largely unknown. Here, we estimated the numbers of PSB and abundances of P-cycling-related genes (i.e., gcd and bpp) in soil aggregates under different fertilization regimes as well as P-solubilizing performance and plant-growth-promoting ability of PSB. We found that tricalcium phosphate-solubilizing bacteria, phytate-degrading bacteria, and gcd and bpp abundances were more abundant in silt plus clay (silt+clay; <53 μm) than in macroaggregate (250 to 2000 μm) and microaggregate (53 to 250 μm). Fertilization treatment and aggregate fractionation showed distinct effects on PSB number and P-cycling-related gene abundance. We found significantly negative correlation between gcd gene abundance and tricalcium phosphate-solubilizing bacterial number (Col-CaP) and dramatically positive correlation between bpp gene abundance and phytate-degrading bacterial number (Col-Phy). P fractions were responsible for PSB number and P-cycling-related gene abundance. The isolated Pseudomonas sp. strain PSB-2 and Arthrobacter sp. strain PSB-5 exhibited good performances for solubilizing tricalcium phosphate. The inoculation of Pseudomonas sp. PSB-2 could significantly enhance plant fresh weight, plant dry weight, and plant height. Our results emphasized distinct distribution characteristics of PSB and P-cycling-related genes in soil aggregates and deciphered a close linkage between PSB number and P-cycling-related gene abundance. Our findings might guide the isolation of PSB from agricultural soils and provide a candidate plant-growth-promoting bacterium for agro-ecosystems.IMPORTANCE Phosphate-solubilizing bacteria are responsible for inorganic P solubilization and organic P mineralization. Elucidating the linkage between phosphate-solubilizing bacterial number and P-cycling-related gene abundance is important to isolate plant-growth-promoting bacteria for agro-ecosystems. Our findings reveal differentiating strategies of phosphate-solubilizing bacteria in soil aggregates, and the deciphered P fractions show strong effects on distribution patterns of phosphate-solubilizing bacteria and P-cycling-related genes. Additionally, we isolated phosphate-solubilizing bacteria with good plant-growth-promoting ability. This study enriches our knowledge of P cycling in soil aggregates and might guide the production and management of farmland.

Isolation and identification of phosphate solubilizing bacteria from the rhizosphere of rice in organic and non-organic rice fields in Sukoharjo District, Indonesia

Abstract. Purwanti D, Setyaningsih R, Susilowati A. 2019. Isolation and identification of phosphate solubilizing bacteria from the rhizosphere of rice in organic and non-organic rice fields in Sukoharjo District, Indonesia. Bonorowo Wetlands 9: 108-115. One of the essential nutrients in the soil is phosphate. Phosphate fertilization is often inefficient because phosphate is bound and difficult for plants to absorb. The use of phosphate solubilizing bacteria (PSB) can be used as an alternative to the availability of P in the soil. This study aimed to obtain PSB isolates with high phosphate solubilization ability and identify these PSB isolates molecularly. Soil samples were taken from organic and non-organic rice (Oryza sativa L.) fields in Sukoharjo, Central Java, Indonesia, namely Grogol Village, Menuran Village, and Pondok Village. The research activity was carried out in several stages: isolation of PSB on Pikovskaya medium, characterization and testing of PSB in dissolving P, and Gram staining. PSB colonies with a phosphate solubilization index and showed different colony colors were taken, and then DNA was isolated. DNA isolation was carried out by extraction method using a DNA extraction kit. The gene encoding 16S rRNA amplified the obtained DNA samples. Sequencing was carried out using a genetic analyzer. Data analysis by comparing sequence data on the BLASTN program. Based on the isolation of rhizosphere samples from organic paddy fields, 14 isolates of PSB were obtained, and ten isolates of non-organic paddy were PSB. P13, P1, Q7, and Q8 isolates had the highest P solubilization ability with dissolution index (IP), namely 3.35, 2.13, 1.82, and 1.47. The 16S rRNA gene sequence analysis showed that isolates P1 and P13 had 99% similarity to Acinetobacter sp. ADP1 strain. The isolate Q7 had a 96% similarity with the genus Clavibacter strain NCPPB 382, ??while Q8 had a 99% similarity with Pseudomonas aeruginosa strain PAO1.

Isolation of phosphate solubilizing bacteria from root rhizosphere to supplement biofertilizer

In soil, a large amount of supplemented phosphorus (P) are immediately transferred into insoluble forms and only 0.1 % of them is available for plant uptake. Therefore, exploring naturally occurring phosphate-solubilizing microorganisms is an essential activity to exploit them in reducing mineral phosphorus added to agricultural soils. In this study, we screened and isolated 7 bacteria that solubilized phosphate at different phosphate solubilization indexes, ranging from 4.2 to 226.1. Of them, the most efficient isolate is PSB31, which solubilized tri calcium phosphate (Ca3(PO4)2 at a rate of 962 mg l-1 and molecularly identified as Bacillus sp. (in: Bacteria) strain IMAU61039. This bacterial strain generated the low supernatant pH and the phosphatase, which are involved in the phosphorus solubilization mechanism. Furthermore, greenhouse experiments showed that tomato seedlings grown in PSB31-inoculated soil contained higher P amount and had much higher biomass than those plants grown in soil without PSB31 addition. These results suggest that the PSB31 strain has potential use as a biofertilizer.

Selective Enrichment Method for Isolation of Efficient Phosphate Solubilizing Bacteria from Soil

ABSTRACT Isolation and screening of phosphate solubilizing bacteria (PSB) seems to become cumbersome using conventional methods, and there may be a chance to lose the more potent isolates during the screening methodology. To overcome these problems, a selective enrichment method has been developed to isolate and screen efficient PSB from diverse sources. Initially, this method includes enrichment of the phosphate solubilizers in the sample followed by selective isolation and screening. Looking into the physico-chemical data, it was revealed that the soil samples from cultivated soil were found to support growth and development of microbial life in general compared to soil samples from non-cultivated stringent environment, which was reflected in number of PSB isolated, or in some samples, PSB may not be obtained. Here, the selective enrichment method developed for isolation of PSB from stringent environmental samples yielded numerically higher number (14) of phosphate solubilizer isolates in comparison to conventional methods (4) from different soil sources. Moreover, isolates obtained following selective enrichment were found consistence for phosphate solubilization in different conditions and for different sources. In contrast to conventional isolation methodologies, the selective enrichment method consistently performed best for PSB isolation particularly from stringent habitats, i.e. mining region where conventional method/s did not perform well.

Isolation, Population, and Selection of Phosphate Solubilizing Bacteria from Acid Soils of Institut Teknologi Sumatera’s Region, Lampung

Ultisol, which is acidic soil, is widely distributed in Indonesia, especially Sumatera Island. The characteristics of acidic ultisol make the presence of phosphate available in the soil deficient. This condition is caused by soil pH, which is very influential in phosphate availability in the soil. In acidic conditions, phosphate (P) binds to Fe or Al. Plants highly need the availability of phosphate in the soil. This condition is because phosphate is a nutrient that is needed by plants. Phosphate solubilizing bacteria are soil microbes that can improve P’s availability in acid soils by dissolving P that is bound to other metals. This study aims to obtain indigenous phosphate solubilizing bacteria from acid soils located in the Institut Teknologi Sumatera (ITERA). The study was conducted from April to June 2019, which included isolation of phosphate solubilizing bacteria from the soil, a test of the ability of phosphate dissolution on Pikovskaya medium, and pathogenicity test on potato tubers. The results showed that there were 35-74 x 105 cfu/g of soil samples. Seventeen isolates were obtained, which were able to use phosphate in the medium. Of the seventeen isolates, there were four potential isolates with the highest phosphate solubility index, namely EF.NAP 1 (1.2143), EF.NA3 (1,100), EF.NAP 4 (0.8616) and EF.NAP 9 (0.7188). Isolates have the best phosphate solubilizing index on the 6th day to the 7th day. The four potential isolates were not pathogenic in pathogenicity testing using potato tubers. These four isolates can be used to isolate candidates to improve the availability of phosphorus in the soil needed by plants in the ITERA region.

Utilization of indigenous phosphate-solubilizing bacteria to optimize the use of coal fly ash for increasing available-P in an Ultisol

Coal fly ash (CFA) is a coal-burning by-product containing macro and micronutrients, and it is the potential material for improving available P in Ultisols. Phosphate-solubilizing bacteria (PSB) play a role in phosphorus solubilization. This study aimed at elucidating the potential use of phosphate-solubilizing bacteria to optimize the use of coal fly ash for increasing soil available P. This study was conducted in two stages, namely isolation of indigenous PSB from an Ultisol and application of the PSB and CFA to improve soil available P. Five indigenous PSB isolated from the soil had the ability to dissolve phosphate. Isolate B5 could dissolve 9.89 ppm P and had a 99.57% closeness to Pseudomonas stutzeri. The application of 20 and 40 t CFA ha-1 increased the soil pH by 4.2% and 7.2%, respectively. Increasing the dose of CFA decreased the content of available P by 50.6%. However, the combination of PSB and 20 t CFA ha-1 increased soil available P, plant growth, plant dry biomass, and P-uptake by plant.

Potential phosphate solubilizing bacteria from the rhizosphere of Cotylelobium melanoxylon tree

Microorganism have important roles in soil cycles and plant living activities. Phosphate solubilizing bacteria is one of the microorganisms in the soil that plays a role in helping provide phosphorus nutrients that are not available to plants. The purpose of this study was to obtain potential phosphate solubilizing bacteria from the rhizosphere Cotylelobium melanoxylon plants. Soil samples were taken in a composite at a depth of 0-20 cm from the rhizosphere area of C. melanoxylon plants in the village of Bona Lumban, Tukka District, Tapanuli Tengah Regency, North Sumatra. Isolation of phosphate solubilizing bacteria using the dilution plate technique with Pikovskaya medium. Phosphate solubilizing bacterial isolates were selected qualitatively by measuring the ratio of the clear zone. Selected isolates are identified up to species molecularly. The isolation results obtained were 16 isolates of phosphate solubilizing bacteria with a clear zone ratio varying between 1.03 to 1.68. Four isolates were selected with the highest clear zone ratio. Based on molecular identification, the four isolates included Pseudomonas aeruginosa species.

Isolation of phosphate solubilizing bacteria from the rhizosphere of local aromatic rice in Bada Valley Central Sulawesi, Indonesia

Phosphate Solubilizing Bacteria (PSB) can be used to increase the efficiency and availability of P in the soil as it can help the process of releasing the bound of P elements so that they become available to the plants. This study aims to isolate and determine the morphological characteristics of the PSB colonies in the rhizosphere of the local aromatic rice plant, analyze the phosphate solubility of each isolate. A total of eleven rhizospheres bacterial were successfully isolated from the local aromatic rice rhizosphere. The morphological characteristics, including the size, edge, shape, elevation, and color of the colony, were obtained vary. The bacteria found were gram-positive and gram-negative, which are 81.81% and 18.18%, respectively. The result of the catalase reaction test showed 72.72% positive and 27.27% negative catalase. Furthermore, eight bacterial isolates formed a clear zone with an area of 0.84–2.66 cm. The Phosphate solubility was 116.67–133.00, and the Phosphate dissolving index was 2.17–2.33 at acidic pH between 4.27–5.67. The concentration of dissolved phosphate was 5.152 mg L−1 – 9.382 mg L−1. The results showed that the PSB has a potential being an alternative way to be developed as a biological fertilizer agent in supporting sustainable agriculture.

Isolation of phosphate-solubilizing bacteria from subtropical soils with different fertilization histories

Phosphorus is one of the most abundant chemical elements but has a low bioavailability index. Therefore, microrganisms play a fundamental role in providing insoluble phosphorus to plants. The objective of this study was to evaluate the capacity of bacteria to solubilize inorganic phosphates in soils with different fertilization histories. Soil and rhizosphere samples were collected from a Red Distroferric Latosol, including a control without mineral or organic fertilizer (C), treatment with mineral fertilizer (MF) according to the needs of each crop, and treatment with organic fertilizer [300 m3 ha-1 of swine wastewater (SW)]. The medium containing calcium phytate presented more colony-forming units (CFU) for all fertilization histories, and growth in treatments C and MF was 50% higher than treatment with SW. CFU values in soils treated with SW were lower than those in the other treatments, and the diversity of insoluble phosphate-solubilizing bacteria (PSB) was higher in treatment C. These results indicate a negative relationship between phosphorus concentrations and the number of PSB.

Aislamiento de bacterias solubilizadoras de fosfato nativas de la ciénaga de mallorquín en el departamento del atlántico-colombia

Las Bacterias Promotoras del Crecimiento Vegetal (PGPR) en el ecosistema de manglar de la ciénaga de Mallorquín desarrollan importantes interacciones con las plantas, entre las que se encuentran las bacterias solubilizadoras de fosfato que desempeñan un importante papel en el suministro de fósforo soluble. Se realizó un aislamiento primario de bacterias solubilizadoras de fosfato a partir de muestras de suelo rizosférico y de lodos. Dichas muestras fueron recolectadas en cinco puntos equidistantes de la ciénaga de Mallorquín en el departamento del Atlántico, Colombia, con el fin de aportar elementos y datos de la presencia de microorganismos con potencial biofertilizante que puedan emplearse para mejorar el crecimiento y desarrollo de los cultivos a futuras investigaciones derivadas del tema en la ciénaga. Teniendo en cuenta que por las condiciones económicas, geográficas y sociales del territorio en el cual se encuentra inmerso el manglar ha sido imposible una caracterización profunda de su biodiversidad. Conociendo necesidad del uso de fertilizantes por el sector agrícola, y de los impactos positivos que tienen estas bacterias sobre las plantas y el ambiente, su recuperación en la ciénaga da vía a la idea de utilizar las bacterias aisladas en el laboratorio para promover el crecimiento de cultivos de interés agroindustrial y de disminuir el uso de sustancias químicas con impactos poco deseables.

Phenotypic and genotypic characterization of phosphate solubilizing bacteria and their efficiency on the growth of maize.

Phosphate solubilizing bacteria (PSB) has ability to convert insoluble form of phosphorous to an available form. Applications of PSB as inoculants increase the phosphorus uptake by plant in the agriculture field. In this study, isolation and identification of PSB were carried out in Indian agriculture field (Nainital region, Uttarakhand). A total of 8 phosphate solubilizing bacterial colonies were isolated on the Pikovskaya’s (PKV) agar medium, containing insoluble tricalcium phosphate (TCP). The colonies showed clear halo zones around the bacterial growth were considered as phosphate solubilizers. Out of 8 bacterial isolates, 3 isolates showed high phosphate solubilization index (PSI) ranged from 4.88 ± 0.69 to 4.48 ± 0.30, lower pH ranging 3.08 ± 0.08 to 3.82 ± 0.12 and high phosphate solubilization varied from 305.49 ± 10 μg/ml to 277.72 ± 1.45 μg/ml, were selected for further characterization. Based on the 16 S rRNA gene sequence analysis A4 isolate and H6 isolate were closely related to Alcaligenes aquatilis (99%), and C1 isolate was closely related to Burkholderia cepacia (99%). In addition, pot examination also showed the greatest efficiency in promotion of maize growth compared to uninoculated plant. Isolated PSB were able to produce different organic acids (such as gluconic acids, formic acid, and citric acid) in the culture supernatant and may consider as the principle mechanism for phosphate solubilization. This study clearly indicates that A4, C1 and H6 isolates may use as a biofertilizers in ecological agricultural systems instead of synthetic chemicals and may help to sustain environmental health and soil productivity.

Isolation of Phosphate Solubilizing Bacteria from White Lupin (Lupinus albus L.) Rhizosphere Soils Collected from Gojam, Ethiopia

Phosphorus is an essential macronutrient. A great portion of phosphorus from chemical fertilizers becomes insoluble and unavailable to plants because of its conversion into salts. Phosphate solubilizing microorganisms as a phosphorus biofertilizer improve soil fertility by solubilizing insoluble phosphate salts and increase crop production. This research aimed in isolation and characterization of phosphate solubilizing bacteria. Sixtythree soil samples collected from seven different parts of white lupin growing areas of Gojam, Ethiopia. Halo zone formation and plate screening method used for isolation. Based on halo zone formation; 152 phosphate solubilizing bacterial isolates obtained. Based on their solubilization index four isolates selected for subsequent experiments and characterization. The four selected isolates tested for their solubilization efficiency on solid media. Isolates HUPSB-35 and HUPSB-45 appeared maximum solubilization index (4.5 mm). Isolate HUPSB-57 was unique with its colony formation; salt tolerance (able to grow up to 10%) and utilization of wide range of carbon sources (utilize all the tested sugars). Isolate HUPSB-27 showed a wide range of pH and temperature preference (100% growth at 10, 15, 20, 25 and 30°C in all tested pH).

Isolation of phosphate solubilizing bacteria and total heterotrophic bacteria from river water and study of phosphatase activity of phosphate solubilizing bacteria

Water samples from the river Ganga at Tribeni, West Bengal, India were sampled monthly to enumerate total heterotrophic bacteria (THB) and phosphate solubilizing bacteria (PSB) between January 2011 and December 2011. THB was high in the month of March and PSB was high in the month of July. The population density of THB ranged from 4.84-5.84x104 cells/ml and that of PSB ranged from 2.14-2.72x102 cells/ml. A significant variation in the capacity to solubilize phosphorous by the isolates of PSB were noted. The phosphatse activity of the isolates exhibited that the strain RPSB6 (27.38 μmoles/g/h) had higher activity followed by the strain RPSB9 (20.92 μmoles/g/h).

Phylogenetic relationship of phosphate solubilizing bacteria according to 16S rRNA genes.

Phosphate solubilizing bacteria (PSB) can convert insoluble form of phosphorous to an available form. Applications of PSB as inoculants increase the phosphorus uptake by plant in the field. In this study, isolation and precise identification of PSB were carried out in Malaysian (Serdang) oil palm field (University Putra Malaysia). Identification and phylogenetic analysis of 8 better isolates were carried out by 16S rRNA gene sequencing in which as a result five isolates belong to the Beta subdivision of Proteobacteria, one isolate was related to the Gama subdivision of Proteobacteria, and two isolates were related to the Firmicutes. Bacterial isolates of 6upmr, 2upmr, 19upmnr, 10upmr, and 24upmr were identified as Alcaligenes faecalis. Also, bacterial isolates of 20upmnr and 17upmnr were identified as Bacillus cereus and Vagococcus carniphilus, respectively, and bacterial isolates of 31upmr were identified as Serratia plymuthica. Molecular identification and characterization of oil palm strains as the specific phosphate solubilizer can reduce the time and cost of producing effective inoculate (biofertilizer) in an oil palm field.

Tricalcium phosphate is inappropriate as a universal selection factor for isolating and testing phosphate-solubilizing bacteria that enhance plant growth: a proposal for an alternative procedure

Literature analysis and chemical considerations of biological phosphate solubilization have shown that the commonly used selection factor for this trait, tricalcium phosphate (TCP), is relatively weak and unreliable as a universal selection factor for isolating and testing phosphate-solubilizing bacteria (PSB) for enhancing plant growth. Most publications describing isolation of PSB employed TCP. The use of TCP usually yields many (up to several thousands per study) isolates “supposedly” PSB. When these isolates are further tested for direct contribution of phosphorus to the plants, only a very few are true PSB. Other compounds are also tested, but on a very small scale. These phosphates (P), mainly Fe-P, Al-P, and several Ca-P, are even less soluble than TCP in water. Because soils greatly vary by pH and several chemical considerations, it appears that there is no metal-P compound that can serve as the universal selection factor for PSB. A practical approach is to use a combination of two or three metal-P compounds together or in tandem, according to the end use of these bacteria—Ca-P compounds (including rock phosphates) for alkaline soils, Fe-P and Al-P compounds for acidic soils, and phytates for soils rich in organic P. Isolates with abundant production of acids will be isolated. This approach will reduce the number of potential PSB from numerous isolates to just a few. Once a potential isolate is identified, it must be further tested for direct contribution to P plant nutrition and not necessarily to general growth promotion, as commonly done because promotion of growth, even by PSB, can be the outcome of other mechanisms. Isolates that do not comply with this general sequence of testing should not be declared as PSB.

Isolation of Phosphate-Solubilizing Bacteria from Different Fields Crop Productions

Isolation of Phosphate-Solubilizing Bacteria from Different Fields Crop Productions

Isolation and Characterization of a Phosphate-Solubilizing Halophilic BacteriumKushneriasp. YCWA18 from Daqiao Saltern on the Coast of Yellow Sea of China

Phosphate-solubilizing bacteria (PSB) function in soil phosphorus cycle, increasing the bioavailability of soil phosphorus for plants. Isolation and application of salt-tolerant or halophilic PSB will facilitate the development of saline-alkali soil-based agriculture. A moderately halophilic bacterium was isolated from the sediment of Daqiao saltern on the eastern coast of China, which also performs phosphate-solubilizing ability. The bacterium was assigned to genus Kushneria according to its 16S rRNA gene sequence, and accordingly named as Kushneria sp. YCWA18. The fastest growth was observed when the culturing temperature was 28°C and the concentration of NaCl was 6% (w/v). It was founds that the bacterium can survive at a concentration of NaCl up to 20%. At the optimum condition, the bacterium solubilized 283.16 μg/mL phosphorus in 11 days after being inoculated in 200 mL Ca3(PO4)2 containing liquid medium, and 47.52 μg/mL phosphorus in 8 days after being inoculated in 200 mL lecithin-containing liquid medium. The growth of the bacterium was concomitant with a significant decrease of acidity of the medium.