Chrome Azurol Research Articles

Naked-Eye Detection of Aluminum in Gastric Drugs on a Paper-Based Analytical Device

This communication describes a method to detect aluminum in gastric drugs by the naked eye using a microfluidic paper-based analytical device (μPAD). Aluminum ions react with chrome azurol S (CAS) and cetyltrimethylammonium bromide (CTAB) to form a colored complex, which generates a colored band on the μPAD. A printed ruler can be used to measure the length of the colored band on an individual paper channel for the quantification of an aluminum ion. The μPAD system was designed for use in a modern instrumental analysis course taken by students majoring in Food Quality and Safety. This analytical protocol could also be modified to be used as a demonstration or laboratory experiment in a high school chemistry course with some simplifications to the procedures.

2606. A Divergent Ferrichrome Receptor Associated with an Insertional Element (IS3) Identified on Novel Locus in Clinical Strain of Pseudomonas aeruginosa

Background Pseudomonas aeruginosa is an aerobic Gram-negative bacterium that causes life-threatening acute and chronic infections in humans. Genotypic mutations and phenotypic variations are key features of its antimicrobial resistance and adaptation to the host environment. Pyoverdine associated genes and divergent receptors play a key role in acute Pseudomonas infections. This study seeks to address the heterogeneity of ferrichrome-iron receptor (fpvA) expression, its effect on pathogenicity and its propensity to cause acute infections clinically. Genetic and phenotypic variation of a clinical isolates of P. aeruginosa (PA097 and PA115) were identified by complete genome sequencing method.MethodsAn IRB-approved prospective study collected 38 P. aeruginosa clinical isolates and stored at Carilion Medical Center. Two genetically unrelated clinical strains were selected from tracheal aspirates: PA097 and PA115. These isolates were characterized by pyoverdine (pvd) quantification in planktonic culture filtrate at OD405 nm. Multiplex PCR was carried out using primers for fpvA receptors. Quantification of iron acquisition was done on chrome azurol S (CAS) agar. Genomes for PA115 and PA097 were sequenced by Illumina Next-generation DNA sequencing.ResultsGenome assembly shows a 6.3 Mb genome size in PA115 with G+C content of 66.4%. Seven insertion sequence elements were located. We found a 101 kb locus for pvD and a highly diversified fpvA associated with an insertional element (IS3). PA115, exhibits rich green pigment of pvd followed by PAO1 and PA097 in LB media (Figure 1A) and also in Planktonic culture filtrate (Fig 1B) for quantitative estimation of pvd (Figure 1C). On CAS agar, PA115 showed high uptake of iron by orange pigment compared with lower pigmentation in PAO1 and PA097 (Fig 1D). We confirmed the ferrichrome-iron receptor as fpvAIIb in PA115 by Multiplex PCR seen in sequencing of PA115 (Figure 2).ConclusionWe found high genetic and phenotypic variation in clinical isolate of P. aeruginosa (PA115) from an acute pneumonia patient. The novel IS element found in its receptor gene locus suggests an increased role in pvd expression and iron uptake from the host. Increased pvd expression and diversified fpvAIIb association with an IS3 element may indicate higher virulence in the PA115 strain. Disclosures All authors: No reported disclosures.

Extraction and derivative spectrophotometric assay of Sm(III), Pr(III) and Nd(III) from REEs monazite concentrate

ABSTRACT Concerning the great significance of rare-earth elements (REEs) in high-technology field and nuclear power, the target of this work is selective extraction and accurate spectrophotometric determination of Sm (III), Pr (III) and Nd (III) from REEs monazite concentrate using Cyanex 921 as extractant and Chrome azurol S dye. Effects of different extraction parameters were evaluated. To elucidate the selectivity and overcoming spectral interferences, derivatisation of spectra was studied. The fourth-derivative spectra were investigated to eliminate interferences of Sm (III), Pr (III) and Nd (III) in presence of each other after their extraction by Cyanex 921 and gave significant peaks for Sm (III), Pr (III) and Nd (III) at 315, 309 and 318 nm, respectively. The optimum parameters for extraction by Cyanex 921 and fourth-derivative spectra using Chrome azurol S dye were applied for the determination of Sm (III), Pr (III) and Nd (III) in REEs monazite concentrate with accurate results.

Inhibitory Abilities of Bacillus Isolates and Their Culture Filtrates against the Gray Mold Caused by Botrytis cinerea on Postharvest Fruit.

Botrytis cinerea, a major phytopathogenic fungus, has been reported to infect more than 200 crop species worldwide, and it causes massive losses in yield. The aim of this study was to evaluate the inhibitory abilities and effects of Bacillus amyloliquefaciens RS-25, Bacillus licheniformis MG-4, Bacillus subtilis Z-14, and Bacillus subtilis Pnf-4 and their culture filtrates and extracts against the gray mold caused by B. cinerea on postharvest tomato, strawberry, and grapefruit. The results revealed that the cells of Z-14, culture filtrate of RS-25, and cells of Z-14 showed the strongest biocontrol activity against the gray mold on the strawberry, grape, and tomato fruit, respectively. All the strains produced volatile organic compounds (VOCs), and the VOCs of Pnf-4 displayed the highest inhibition values. Based on headspace solid-phase microextraction in combination with gas chromatography-mass spectrometry, esters accounted for the largest percentage of the VOCs produced by RS-25, MG-4, Z-14, and Pnf-4 (36.80%, 29.58%, 30.78%, and 36.26%, respectively). All the strains showed potent cellulase and protease activities, but no chitinase activity. RS-25, Z-14, and MG-4, but not Pnf-4, grew on chrome azurol S agar, and an orange halo was formed around the colonies. All the strains showed biofilm formation, fruit colonization, and lipopeptide production, which may be the main modes of action of the antagonists against B. cinerea on the fruit. This study provides the basis for developing natural biocontrol agents against the gray mold caused by B. cinerea on postharvest fruit.

Phosphates solubilization, indol-3-acetic acid and siderophores production by Beauveria brongniartii and its effect on growth and fruit quality of Capsicum chinense

ABSTRACTSolubilization of inorganic P-sources and production of siderophores and indole-3-acetic acid (IAA) by Beauveria brongniartii were quantified and then, the effects of biofertilization using B. brongniartii on the plant growth, fruit yield and quality of Capsicum chinense were evaluated. Beauveria brongniartii solubilized more P from Ca3(PO4)2 (158.95 mg L−1) than FePO4 (31.7 mg L−1) and produced siderophores (59.8% of Fe3+-Chrome azurol-S degradation) and IAA (31.2 mg L−1). Plants fertilised at 100% of the recommended dosage (120N-150P-150K) had the tallest height at 30 (37.56 cm, P = 0.0494), 45 (57.56 cm, P = 0.0510) and 60 (67.87 cm, P = 0.0461) days after transplanting (dat) compared to plants inoculated and fertilised at 75% (90N-112.5P-112.5K) during the same period (30 dat = 30.68 cm, 45 dat = 45.81 and 60 dat = 55.75 cm). Inoculated plants with B. brongniartii had a higher foliar N content (3.53%, P = 0.0532) than non-inoculated plants (3.31%). The fruit weight (FW = 6.767 g, P = 0.00001), longitudinal fruit diameter (LFD = 37.82 mm, P = 0.0001) and equatorial fruit diameter (EFD = 25.59 mm, P = 0.0003) were also higher in inoculated versus non-inoculated plants (FW = 5.632 g, LFD = 33.98 mm and EFD = 24.10 mm). The P-solubilizing ability and siderophore and IAA production of B. brongniartii played an important role in the plant growth, foliar nutrient content and fruit quality of C. chinense plants.

Spectrophotometric determination of cationic surfactants in aqueous media using chrome azurol S as colour forming agent and 1-butanol as extracting solvent

A simple spectrophotometric method for the determination of cationic surfactants (CS) is developed using an anionic dye, chrome azurol S (CAS) as an ion-association complex forming agent, and 1-butanol as an extracting solvent. In the aqueous solution CS such as cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC) and dodecyltrimethylammonium bromide (DTAB) reacts with CAS to form an ion-association complex which is extracted into 1-butanol to form a pink-violet coloured organic phase. The final concentration of CAS in surfactant solution is 165 μM. The pH of the medium is maintained at ~6.4. The coloured compound exhibits maximum absorbance at 520 nm with a molar absorption coefficient in the range of (2.6–2.9) × 104 L mol−1 cm−1. Beer's law is obeyed in the concentration range of 0–82 μM, 0–88 μM and 0–84 μM for CTAB, CPC and DTAB, respectively in normal condition. However, to minimize the interference of cations, the masking with EDTA has been proposed. In case of CTAB determination in EDTA masked double distilled water, the linear dynamic range (LDR) is found as 27–55 μM. The proposed method is rapid, user-friendly and economical. The method is applied in mixed CS systems, and it showed good results. To check the reliability of the method, it has been applied for CS determination in real water samples masked with EDTA and spiked with CS of known concentration. The results obtained for recovery are quite satisfactory.

Nocardamin glucuronide, a new member of the ferrioxamine siderophores isolated from the ascamycin-producing strain Streptomyces sp. 80H647.

A new siderophore glucuronide, nocardamin glucuronide (1), was isolated together with nocardamin (2) by applying the one strain-many compounds (OSMAC) approach to the ascamycin-producing strain, Streptomyces sp. 80H647, and performing multivariate analysis using mass spectral data. Structure elucidation was accomplished by a combination of NMR and MS analyses. The absolute configuration of the glucuronic acid moiety was found to be β-D-GlcA by hydrolysis using β-glucuronidase, subsequent derivatization of the hydrolysate, and comparison with standards. The siderophore activity of 1 was evaluated through the chrome azurol S assay and was comparable to that of 2 and deferoxamine (IC50 13.4, 9.5, and 6.3 μM, respectively). Nocardamin glucuronide (1) is the first example of a siderophore glucuronide.

Efficient entrapment and separation of anionic pollutants from aqueous solutions by sequential combination of cellulose nanofibrils and halloysite nanotubes

The synergistic combination of different nanomaterials for improved performance in environmental applications such as the removal of aqueous micropollutants has attracted increasing interest in recent years. This study demonstrates a novel sequential adsorption–aggregation concept that harnesses tubular halloysite nanotubes (HNTs) and flexible cellulose nanofibrils (CNFs) for the removal of a small, anionic dye molecule, chrome azurol S, from water. Hollow HNTs were first allowed to interact with the aqueous dye solution, after which the dye-loaded colloidal nanotubes were aggregated and separated from the water phase with cationized CNFs. The combination of 25 mg CNFs with 1 g HNTs at pH 7 resulted in efficient removal of dye (80%) and turbidity (~100%) and the removal of dye was further promoted in more acidic conditions (within the pH range of 6–8.5) because of the attractive electrostatic interactions. Cationic CNFs not only enabled the separation of dye-loaded clay particles from the water phase through a rapid aggregation but also participated in dye removal through adsorption (~20%). In comparison with nano-sized HNTs, the dye removal performance of micro-sized and chemically similar kaolin was poor (43%). Given the good availability of both HNTs and CNFs and the low consumption of the more expensive component (i.e., CNFs) in the process, the concept is straightforward, readily applicable, environmentally benign, and potentially cost-effective.

Amberlite XAD-2010 Impregnated with Chrome Azurol S for Separation and Spectrophotometric Determination of Uranium and Thorium

A new extractant-impregnated resin (EIR), chrome azurol S-impregnated on XAD-2010, is used as an adsorbent to separate and preconcentrate U(VI) and Th(IV) ions prior to their spectrophotometric determination. Various instrumental techniques such as elemental analysis, FTIR, and SEM analysis were employed for full characterization of the synthetic extractant. Optimization of the adsorption and elution conditions of U(VI) and Th(IV) ions using synthesized chrome azurol S-impregnated XAD-2010 were studied. Langmuir isotherm model has the best fitting experimental data with a maximum adsorption capacity of 23.8 mg g−1 for U(VI) and 25.4 mg g−1 for Th(IV). The adsorption process of each metal ion using synthesized chrome azurol S-impregnated XAD-2010 showed an exothermic pseudo-second-order adsorption process. High tolerance limits for several studied metal ions on chrome azurol S-impregnated XAD-2010 were observed. The optimized method was applied on an international certified samples and different rock types bearing thorium and uranium with accurate results.

Comparison of five bacterial strains producing siderophores with ability to chelate iron under alkaline conditions

Iron deficiency is one of the main causes of chlorosis in plants, which leads to losses in field crops quality and yield. The use of synthetic chelates to prevent or correct iron-deficiency is not satisfactory mainly due to their poor biodegradability. The present work aimed to search suitable microorganisms to produce alternative, environment-friendly iron-chelating agents (siderophores). For this purpose, the performance of five bacteria (Azotobacter vinelandii, Bacillus megaterium, Bacillus subtilis, Pantoea allii and Rhizobium radiobacter) was evaluated, regarding siderophore production kinetics, level of siderophore production (determined by chrome azurol S, CAS method), type of siderophore produced (using Arnow and Csaky’s tests) and iron-chelating capacity at pH 9.0. All bacteria were in stationary phase at 24 h, except A. vinelandii (at 72 h) and produced the maximum siderophore amount (80–140 µmol L−1) between 24 and 48 h, with the exception of A. vinelandii (at 72 h). The analysis of culture filtrates revealed the presence of catechol-type siderophores for B. subtilis and R. radiobacter and hydroxamate-type siderophores for B. megaterium and P. allii. In the case of A. vinelandii, both siderophore-types (catechol and hydroxamates) were detected. The highest iron-chelating capacity, at pH 9.0, was obtained by B. megaterium followed by B. subtilis and A. vinelandii. Therefore, these three bacteria strains are the most promising bacteria for siderophore production and chlorosis correction under alkaline conditions.

CARACTERIZACIÓN DE BACTERIAS RIZOSFÉRICAS DE SUELO CIRCUNDANTE A UNA PLANTA RECICLADORA DE PLOMO (Pb)

The aim of this research was to isolate and characterize rhizosphere bacteria of huizache ( Acacia farneciana ) and mesquite ( Prosopis glandulosa ), predominant vegetation surrounding a lead (Pb) recycling company. Bacteria were evaluated on their tolerance to Pb(NO 3 ) 2 ,andtheircapacity to produce indole-acetic acid (IAA) and siderophores using Salkowski and chrome azurol S (CAS) agar medium techniques, respectively. The bacterial isolates were identified through the 16S rRNA gene. Ten bacterial strains tolerated concentrations between 0.6 and 1.8 mM of Pb (NO 3 ) 2 , of which seven strains had IAA production of up to 60 μg/mL and five strains showed siderophore production. Qualitatively, the bacterial strains L2, L48 and L67 presented a more intense orange halo than the bacterial strains L138 and L23, which indicates a positive reaction of siderophores production. Additionally, the siderophores production of the hydroxamate type produced by the bacterial strains L2, L48, L67, L138 and L23 was variable, between 0.02 and 0.054 μg/mL. The results of this research allow concluding that there are bacterial strains around the lead (Pb) recycling company with a high potential for phytoremediation processes.

Antagonistic activity of marine Streptomyces sp. S073 on pathogenic Vibrio parahaemolyticus

Marine Streptomyces sp. isolate S073 was shown to have strong antagonistic activity towards the pathogenic Vibrio parahaemolyticus using the agar diffusion method. The antagonistic substance(s) secreted into the supernatant was thermostable and non-proteinaceous in nature. S073 was found to produce carboxylate-type siderophores during most of its life cycle using a chrome azurol S assay. The antagonistic activity of S073 was mostly attributed to its higher ability to compete for iron compared with that of V. parahaemolyticus, as deduced from siderophore quantification. Iron supplementation studies indicated that additional mechanisms besides iron competition were simultaneously involved in governing the observed inhibition. Co-culture analysis indicated that S073, although disadvantaged in growth rate, was still competitive in inhibiting vibrios. The promising potential of S073 development as a biocontrol agent in aquaculture was discussed.

Comparative Genomics, Siderophore Production, and Iron Scavenging Potential of Root Zone Soil Bacteria Isolated from 'Concord' Grape Vineyards.

Iron (Fe) deficiency in crop production is a worldwide problem which often results in chlorosis in grapevines, particularly in calcareous soils. Siderophores secreted by microorganisms and Strategy II plants can chelate Fe and other metals in soil solution, and siderophore-Fe complexes can then be utilized by plants and microbes. Plants may also shift rhizosphere conditions to favor siderophore-producing microbes, which can increase plant available Fe. Between-row cover crops (barley, rye, wheat, wheat/vetch) were planted as living mulch to address grapevine chlorosis by enhancing soil health in two vineyards in central Washington. The objectives of the current study were to (1) enrich for siderophore-producing organisms fromwithin the indigenous rooting zone community of 'Concord' grapevines, and (2) perform comparative genomics on putative siderophore producing organisms to assess potentially important Fe acquisition-related functional domains and protein families. A high-throughput, chrome azurol S (CAS)-based enrichment assay was used to select siderophore-producing microbes from 'Concord' grapevine root zone soil. Next-generation whole genome sequencing allowed the assembly and annotation of ten full genomes. Phylogenetic analysis revealed two distinct clades among the genomes using the 40 nearest neighbors available in the public database, all of which were of the Pseudomonas genus. Significant differences in functional domain abundances were observed between the clades including iron acquisition and metabolism of amino acids, carbon, nitrogen, phosphate, and sulfur. Diverse mechanisms of Fe uptake and siderophore production/uptake were identified in the protein families of the genomes. The sequenced organisms are likely pseudomonads which are well-suited for iron scavenging, suggesting a potential role in Fe turnover in vineyard systems.

High-throughput Siderophore Screening from Environmental Samples: Plant Tissues, Bulk Soils, and Rhizosphere Soils

Siderophores (low-molecular weight metal chelating compounds) are important in various ecological phenomenon ranging from iron (Fe) biogeochemical cycling in soils, to pathogen competition, plant growth promotion, and cross-kingdom signaling. Furthermore, siderophores are also of commercial interest in bioleaching and bioweathering of metal-bearing minerals and ores. A rapid, cost effective, and robust means of quantitatively assessing siderophore production in complex samples is key to identifying important aspects of the ecological ramifications of siderophore activity, including, novel siderophore producing microbes. The method presented here was developed to assess siderophore activity of in-tact microbiome communities, in environmental samples, such as soil or plant tissues. The samples were homogenized and diluted in a modified M9 medium (without Fe), and enrichment cultures were incubated for 3 days. Siderophore production was assessed in samples at 24, 48, and 72 hours (h) using a novel 96-well microplate CAS (Chrome azurol sulphonate)-Fe agar assay, an adaptation of the traditionally tedious and time-consuming colorimetric method of assessing siderophore activity, performed on individual cultivated microbial isolates. We applied our method to 4 different genotypes/Lines of wheat (Triticum aestivum L.), including Lewjain, Madsen, and PI561725, and PI561727 commonly grown in the inland Pacific Northwest. Siderophore production was clearly impacted by the genotype of wheat, and in the specific types of plant tissues observed. We successfully used our method to rapidly screen for the influence of plant genotype on siderophore production, a key function in terrestrial and aquatic ecosystems. We produced many technical replicates, yielding very reliable statistical differences in soils and within plant tissues. Importantly, the results show the proposed method can be used to rapidly examine siderophore production in complex samples with a high degree of reliability, in a manner that allows communities to be preserved for later work to identify taxa and functional genes.

Siderophore Detection Using Chrome Azurol S and Cross-Feeding Assays.

More than 500 siderophores that bind ferric iron have been characterized and grouped by type based on their chemical structure. The chrome azurol S (CAS) assay is a universal colorimetric method that detects siderophores independent of their structure. In this assay, siderophores scavenge iron from an Fe-CAS-hexadecyltrimethylammonium bromide complex, and subsequent release of the CAS dye results in a color change from blue to orange. Solution-based experiments with CAS result in a quantitative measure of siderophore production, while an observable color change on CAS agar plates can be performed for qualitative detection of siderophores. Cross-feeding assays are another useful method to detect and characterize siderophores produced by bacteria. Under iron-limiting conditions, cross-feeding assays test the ability of an indicator strain to grow when supplied with a specific siderophore (from a test strain) to which it has a cognate receptor required for import into the cell. The cross-feeding assay can be tested with a variety of wild-type strains, siderophore biosynthesis mutants, and siderophore receptor mutants.

Adaption of microarray primers for iron transport and homeostasis gene expression in Pseudomonas fluorescens exposed to nano iron

Modified protocols were adapted for PCR and culture based methods for the analysis of Pseudomonas fluorescens cells exposed to nanoscale zero-valent iron (NZVI) and iron (Fe) in bacterial growth nutrient media was determined by a modified atomic absorption spectrometric (AAS) analysis method. We adapted sets of microarray primers used to quantify gene expression of pvdS and a bacterioferritin-associated ferredoxin gene for use in real-time quantitative reverse transcription (qRT-PCR) analysis. pvdS is one of a cluster of genes regulating the synthesis of the siderophore pyoverdine that was also measured using chrome azrul S (CAS) plates.•The current protocol provides a detailed qRT-PCR method for quantifying genes involved in the acquisition and utilization of Fe in P. fluorescens cells exposed to NZVI.•The qRT-PCR results were independently corroborated with 2 culture based methods, growth curves and chrome azurol S (CAS) plate.•The modified AAS method was used to measure Fe in Tryptic Soy Broth (TSB) medium where sodium (Na) causes inference in iron measurement.

Zinc Ions Affect Siderophore Production by Fungi Isolated from the Panax ginseng Rhizosphere.

Although siderophore compounds are mainly biosynthesized as a response to iron deficiency in the environment, they also bind with other metals. A few studies have been conducted on the impact of heavy metals on the siderophore-mediated iron uptake by microbiome. Here, we investigated siderophore production by a variety of rhizosphere fungi under different concentrations of Zn²⁺ ion. These strains were specifically isolated from the rhizosphere of Panax ginseng (Korean ginseng). The siderophore production of isolated fungi was investigated with chrome azurol S (CAS) assay liquid media amended with different concentrations of Zn²⁺ (50 to 250 μg/ml). The percentage of siderophore units was quantified using the ultra-violet (UV) irradiation method. The results indicated that high concentrations of Zn²⁺ ion increase the production of siderophore in iron-limited cultures. Maximum siderophore production by the fungal strains was detected at Zn²⁺ ion concentration of 150 μg/ml except for Mortierella sp., which had the highest siderophore production at 200 μg/ml. One potent siderophore-producing strain (Penicillium sp. JJHO) was strongly influenced by the presence of Zn²⁺ ions and showed high identity to P. commune (100% using 18S-rRNA sequencing). The purified siderophores of the Penicillium sp. JJHO strain were chemically identified using UV, Fourier-transform infrared spectroscopy (FTIR), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF-MS) spectra.

Distance readout of Al content with naked eyes on a cotton thread

We described a facile method for distance-based detection of aluminum on a thread based on the adsorption of formed complex onto thread. Chrome azurol S (CAS) containing Cetyltrimethylammonium Bromide (CTMAB) were used as chromogenic reagent, which reacts with aluminum to form AL-CAS-CTMAB complex on a thread. The complex was adsorbed onto thread to generate a colored band. Aluminum contents could be quantified by measuring the length of colored band on the thread using a ruler, thereby eliminating the need for electronic readout devices and trained personnel. This instrument-free method has features of low cost, easy to operation, fast analysis speed, disposability and low reagents/sample consumption. Moreover, considering that the thread fiber has adsorption capability to various molecules such as metal-ligand complexes and biomolecules, we believe that this technique holds the potentials to be widely adaptable to distance-based chemical and biochemical analysis.

Reduced expression of iron transport and homeostasis genes in Pseudomonas fluorescens during iron uptake from nanoscale iron

Plant growth-promoting rhizobacteria (PGPR) have beneficial effects on the host plant that include acquisition of nutrients such as iron (Fe). In this study, the impact of varying concentrations of nanoscale zero-valent iron (NZVI, 1, 2 and 5 g L−1) on a PGPR, Pseudomonas fluorescens' viability, growth and production of siderophores was investigated. Microscale zero-valent iron (MZVI) particles were also included in this study to determine and compare the effects of particle size on Fe acquisition and use by Pseudomonas fluorescens. Siderophores chelate insoluble forms of Fe that are then rendered bioavailable to P. fluorescens as well as some plants. This research indicates that the Fe species derived from lower concentrations of NZVI additions (1 g L−1) are bioavailable and can be utilized as a nutrient by P. fluorescens without the bacteria producing siderophores, an energy intensive process. Also, NZVI application as a fertilizer has promise for better utilization of Fe by plants. P. fluorescens colony forming units (log10 CFU mL−1) growth in cultures containing 1 g L−1 NZVI were significantly higher exceeded (14 units) than those grown without NZVI additions (13 units). The majority of P. fluorescens cells treated with 2 and 5 g L−1 were nonviable and produced limited colony forming units (4 units). The effects of NZVI on siderophore production by P. fluorescens were assessed using chrome azurol S (CAS) plates and real time quantitative reverse transcription PCR (qRT-PCR). Further, expression of genes involved in Fe utilization [putative pvdS (PFL 4190) and a bacterioferritin-associated ferredoxin gene (PFL 4858)] were targeted using real time quantitative reverse transcription PCR (qRT-PCR). Expression of both genes was below detection limits in cultures exposed to NZVI but measurable in MZVI and control treatments, again indicating potential ease in uptake of Fe by P. fluorescens from NZVI. Transmission electron microscopy (TEM) revealed the presence of NZVI particles on the exterior and interior of cells; energy dispersive X-ray spectroscopy (EDS) verified that the material was derived from NZVI and that Fe concentrations were higher in the interior of cells exposed to 1 g L−1 NZVI compared to the control. The research findings from this study indicate that NZVI has the potential to accumulate in plant growth-promoting rhizobacteria and affect the growth of organisms in environments like the rhizobiome which may affect plant growth positively. This research opens up opportunities for future studies to determine the effects of Fe and other nutrients and micronutrients derived from nanomaterials, particularly in oligotrophic systems.

Siderophore Production by Rhizosphere Inhabiting Bacteria and Fungi

The production of siderophores is greater in rhizosphere inhabiting fungi and bacteria. The present work was designed to isolate the rhizosphere inhabiting bacteria and fungi from the rhizosphere of Phaseolus Vulgaris, Pisum sativum, Vicia faba and Alfa alfa. The obtained isolates has been screened for siderophores production using Chrome Azurol Sulfonate assay (CAS). The highest siderophore producer bacterium and fungus has been molecularly identified as Bacillus MG214652 andAspergillus niger MH844535 respectively. They were able to produce 70.4% and 87% units of siderophore respectively. Bacillus MG214652 siderophores was characterized as catecholate type with maximum absorbance at 495 nm. Aspergillus niger MH844535 siderophore was characterized as hydroxymate type with maximum absorbance at 450 nm.