Prospecting the plant growth–promoting activities of endophytic bacteria Cronobacter sp. YSD YN2 isolated from Cyperus esculentus L. var. sativus leaves

Purpose Plant growth–promoting (PGP) bacteria are an environment-friendly alternative to chemical fertilizers for promoting plant growth and development. We isolated and characterized a PGP endophyte, YSD YN2, from the leaves of Cyperus esculentus L. var. sativus. Methods Specific PGP characteristics of this strain, such as phosphate solubilization ability, potassium-dissolving ability, siderophore and indole-3-acetic acid (IAA) production, and salt tolerance, were determined in vitro. In addition, positive mutants were screened using the atmospheric and room temperature plasma (ARTP) technology, with IAA level and organic phosphate solubility as indices. Furthermore, the effect of the positive mutant on seed germination, biomass production, and antioxidant abilities of greengrocery seedling was evaluated, and the genome was mined to explore the underlying mechanisms. Results The strain YSD YN2 showed a good performance of PGP characteristics, such as the production of indole acetic acid and siderophores, solubilization ability of phosphate, and potassium-dissolving ability. It was recognized through 16S rRNA sequencing together with morphological and physiological tests and confirmed as Cronobacter sp. The strain exposed to a mutation time of 125 s by ARTP had the highest IAA and organic phosphate (lecithin) concentrations of 9.25 mg/L and 16.50 mg/L, 50.41% and 30.54% higher than those of the initial strain. Inoculation of mutant strain YSD YN2 significantly increased the seed germination, plant growth attributes, and the activities of peroxidase (POD) and superoxide dismutase (SOD), respectively, but decreased the content of malondialdehyde (MDA) significantly compared with the control. Furthermore, genome annotation and functional analysis were performed through whole-genome sequencing, and PGP-related genes were identified. Conclusion Our results indicated that the mutant strain YSD YN2 with PGP characteristics is a potential candidate for the development of biofertilizers.

The Application of Organic Phosphate Nucleating Agents in Polypropylene with Different Molecular Weights

Two kinds of organic phosphate nucleating agent (NA-11 and NA-21) were used in PP with different molecular weights through the melt extrusion method. The dispersibility of the nucleating agents in PP, and the effect of the nucleating agents on the molecular weight, rheological behavior and crystallization behavior of PP were investigated. SEM and TEM analysis showed that the average radius of the dispersed particles (nucleating agents) was larger in LPP than that in HPP. The good dispersion of NA-21 also created more nucleation embryos for the adsorption of polypropylene molecules than the agglomerated NA-11. The gel permeation chromatography (GPC) analysis showed that the average molecular weight of HPP and LPP both decreased with the addition of a nucleating agent. The rotational rheometer and capillary rheometer analysis showed that the effect of NA-21 on reducing intermolecular entanglement was more significant, whether in HPP or LPP. The addition of NA-21 had less elastic energy storage and better flow stability, and could be processed at a higher speed. Simultaneously, the relaxation time in the blends with LPP was shorter than that with HPP. It was found that the crystallinity and nucleation efficiency of HPP/nucleating agent blends increased remarkably, while there was a barely perceptible increase in LPP/nucleating agent blends.

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 Fe (oxyhydr)oxide morphology on phytic acid transport under saturated flow condition

<p>Natural iron (oxyhydr)oxides are ubiquitous in subsurface environments. Phytic acid (myo-inositol hexaphosphate, IHP), a dominant form of organic phosphate (OP) in organic carbon-rich surface soils, strongly binds with Fe (oxyhydr)oxide. The cotransport of IHP and Fe (oxyhydr)oxide with different morphology under acid and alkaline conditions in the subsurface is mostly overlooked. These cotransport processes are critical for P (bio)geochemical processes in the subsurface that is rich in Fe (oxyhydr)oxides. Three Fe (oxyhydr)oxides (ferrihydrite, hematite, and goethite) were chosen in this study, and the cotransport of IHP and Fe (oxyhydr)oxide was investigated in saturated columns by injecting Fe (oxyhydr)oxide under different IHP concentrations (0, 10, 25, 50, and 100 µM) at pH of 5 and 10. The presence of IHP significantly enhanced the mobility of Fe (oxyhydr)oxide at both pH 5 and 10 due to the stronger electrostatic repulsion between Fe (oxyhydr)oxide and quartz sand. At low IHP concentrations (< 50 µM IHP), goethite with a rod-like morphology showed strong mobility due to its orientation transport along with the water flow streamline. The mobility of amorphous Fe (oxyhydr)oxide, ferrihydrite, was much slower than the goethite. However, ferrihydrite could facilitate more IHP transport due to its sorption capacity for IHP that is higher than goethite and hematite. At high IHP concentrations (> 50 μM), surface precipitation might have occurred on ferrihydrite because of its poorly ordered crystallinity, which contributed to its less negatively charged surface and weak ferrihydrite facilitated IHP transport. The new insight provided in this study is important for evaluating the transport behavior and impact of IHP in a saturated solum rich in Fe (oxyhydr)oxides.</p>

Calcination Activation of Three-dimensional Cobalt Organic Phosphate Nanoflake Assemblies for Supercapacitors

Three-dimensional (3D) metal-organic framework (MOF) assemblies at the micro-nanoscale have garnered considerable interest because of their extensive applications. Herein, 3D cobalt organic phosphate (COP) nanoflake precursors were obtained by a...

Phosphate dynamics in a sub-tropical lake ecosystem

<p>Lake Ecosystem is a key component of biosphere that supports aquatic life and provide sink to the untreated effluent (domestic, industrial, and agricultural). Due to rapid industrialisation and changing climate, 30-40% of the lakes in the world are now eutrophic. The basic cause of eutrophication is the addition of nutrients (nitrogen and phosphate) into the lake system. Phosphate has been observed to be the limiting nutrient in 80% of the lakes and reservoirs in the world. Unlike other elements, phosphate does not escape from the system but changes from one form to the other depending upon the prevailing physico-chemical conditions. Chemical parameters like pH and redox potential are the major governing factors for phosphate fluxes. Sediments in the benthic zone serves as a sink as well as the source of phosphate for the photic zone. In the present study, a relationship between the physico-chemical properties of water and the fractions of phosphate in the sediments were studied. The study was conducted during three different seasons i.e. post-monsoon, winter, and summer to observe the seasonal variation. The pH, DO, ORP, and available phosphate in the water varied from 8.5, 14.7 mg/l, 39 mV, and 5.8 mg/l, 8.4, 3.5 mg/l, -64 mV, and 8.7 mg/l, and 7.8, 7.3 mg/l, 119 mV, and 10.5 mg/l during post-monsoon, winter, and summer, respectively. Phosphate in sediments was fractionated using SMT protocol. It was categorised under inorganic and organic phosphate classes, and the inorganic phosphate was further categorised as Non apatite inorganic phosphate (NAIP: Fe/Al bound) and Apatite inorganic phosphate (AIP: Ca bound).  The inorganic phosphate in the sediments was observed to be more than organic phosphate during post monsoon and summer, and at the same time the available phosphate in the overlying water was found low in concentration. The growth of phytoplankton is constrained by decreasing bio available phosphate in water. Concentration of NAIP was observed to vary with redox potential and concentration of AIP with pH. The study justified the hypothesis of direct relationship of sediment chemistry with bio availability of phosphate in water. Winter was found to be the extreme weather for phosphate fluxes. The findings point towards need of proper management such as chemical precipitation, sediment dredging etc. during this extreme weather conditions.</p>