Oxidation Of Elemental Sulfur Research Articles

Mineralogy of the RBT 04262 Martian meteorite as determined by micro‐Raman and micro‐X‐ray fluorescence spectroscopies

AbstractMartian meteorites and terrestrial analogs represent the only samples available on Earth for studying mineralogy features of our neighbor planet Mars. This work characterizes the Roberts Massif (RBT) 04262 Martian meteorite by using mainly Raman spectroscopy. By means of this technique, it was confirmed that the meteorite matrix is composed by pyroxene and plagioclase (converted to maskelynite due to the shock pressure). Olivine‐coarse grains embedded in the matrix were also observed. These grains were coated by hydrated magnesium and calcium sulfates, which would belong to the Mars sulfate deposits or to the terrestrial weathering. Although the sulfates could be formed on Mars due to the oxidation of sulfides or elemental sulfur along the sulfur Mars cycle, their distribution along cracks and fractures confirm that are weathering products. However, other S‐bearing compounds that belong to Mars were found, such as elemental sulfur and a thermally transformed iron sulfide. Finally, the calcium phosphate merrillite and titanomagnetite were also detected. Taking this into account, the minerals found were classified into primary minerals that belong to Mars (pyroxene, olivine, elemental sulfur, and titanomagnetite), secondary ones that are alteration products of the primary minerals (maskelynite, iron sulfide, and merrillite), and terrestrial weathering products (sulfates gypsum and epsomite).

Organic Amendments and Elemental Sulfur Stimulate Microbial Biomass and Sulfur Oxidation in Alkaline Subtropical Soils

Sulfur deficiency arising due to intensive cultivation, use of sulfur free fertilizers and reduction in atmospheric sulfur depositions has become a major issue limiting crop production in many parts of the world. Elemental sulfur could be a good source of available S, but its slow oxidation is a problem for its efficient use as a sulfur fertilizer. Main objective of the study was to assess the effect of organic amendments (OA) and elemental sulfur (ES) on microbial activities, sulfur oxidation and availability in soil. A laboratory incubation experiment was carried out for a 56 days period using two sulfur deficient alkaline soils. Organic amendments (OA), i.e., farmyard manure (FYM), poultry litter (PL) and sugarcane filter cake (SF), were applied (1% w/w) with or without elemental sulfur (ES) at 50 mg kg−1. Application of ES alone or in combination with OA significantly increasedCO2-C evolution, microbial biomass, and enzyme activities in the soils, except dehydrogenase activity (DHA) which was not affected by ES application. Combined application of OA and ES had a more pronounced effect on microbial parameters compared to ES or OA applied alone. Ratios of dehydrogenase activity-to-microbial biomass C and arylsulfatase activity-to-microbial biomass C were high in ES+FYM and ES+SF treatments, respectively. Elemental sulfur got sufficiently oxidized resulting in significant improvement in plant available S. Relatively more ES was distributed into C-bonded-S than ester bonded-S. Increase in sulfur availability in ES+OA amended soils was the combined function of sulfur oxidation and mineralization processes through improved microbial activity.

Combination application of elemental sulfur and earthworm increased the lead (Pb) uptake by ryegrass (Lolium perenne L.) in contaminated agricultural soil.

The phytoremediation efficiency is largely depends on the bioavailability of heavy metal in soil. The activity of earthworms and oxidation of elemental sulfur (S0) in soil has influence on heavy metal speciation transformation in soil. By conducting pot experiment, we examined the possibility of enhancing phytoextraction efficiency of lead (Pb) in soil by ryegrass (Lolium perenne L.) with application of both S0 and earthworms. Results showed that the addition of S0 decreased soil pH and increased soil CEC, while a slight trend of decrease for soil pH and increase for CEC was found with earthworm application. In soil treated with earthworms, the addition of S0 increased the concentration of DTPA-extractable Pb by 9.9~20.8%. The concentration of diffusive gradients in thin film (DGT)-extractable Pb was increased by 26.31~32.9% with S0 and earthworm addition. In soil treated with earthworms, the addition of S0 increased the concentration of Pb in shoots of ryegrass by 55.7~110.4% and the translocation factor of Pb in ryegrass was also increased by S0 addition. Our results suggested that the combination application of earthworms and S0 could be an effective way to enhance the remediation efficiency of ryegrass for Pb-contaminated soil.

Mimicking the microbial oxidation of elemental sulfur with a biphasic electrochemical cell

The lack of an artificial system that mimics elemental sulfur (S8) oxidation by microorganisms inhibits a deep mechanistic understanding of the sulfur cycle in the biosphere and the metabolism of sulfur-oxidising microorganisms. In this article, we present a biphasic system that mimics biochemical sulfur oxidation under ambient conditions using a liquid|liquid (L|L) electrochemical cell and gold nanoparticles (AuNPs) as an interfacial catalyst. The interface between two solvents of very different polarity is an ideal environment to oxidise S8, overcoming the incompatible solubilities of the hydrophobic reactants (O2 and S8) and hydrophilic products (H+, SO32–, SO42–, etc.). Furthermore, the interfacial AuNPs provide a catalytic surface onto which O2 and S8 can adsorb. Control over the driving force for the reaction is provided by polarising the L|L interface externally and tuning the Fermi level of the interfacial AuNPs by the adsorption of aqueous anions. Comparison of electrochemical measurements using a 4-electrode closed bipolar electrochemical cell and a L|L electrochemical cell confirmed that electron transfer reactions are possible between O2, gold and S8 in biphasic systems.

Microbial chemolithotrophic oxidation of pyrite in a subsurface shale weathering environment: Geologic considerations and potential mechanisms.

Oxidative weathering of pyrite plays an important role in the biogeochemical cycling of Fe and S in terrestrial environments. While the mechanism and occurrence of biologically accelerated pyrite oxidation under acidic conditions are well established, much less is known about microbially mediated pyrite oxidation at circumneutral pH. Recent work (Percak-Dennett et al., 2017, Geobiology, 15, 690) has demonstrated the ability of aerobic chemolithotrophic microorganisms to accelerate pyrite oxidation at circumneutral pH and proposed two mechanistic models by which this phenomenon might occur. Here, we assess the potential relevance of aerobic microbially catalyzed circumneutral pH pyrite oxidation in relation to subsurface shale weathering at Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) in Pennsylvania, USA. Specimen pyrite mixed with native shale was incubated in groundwater for 3months at the inferred depth of in situ pyrite oxidation. The colonized materials were used as an inoculum for pyrite-oxidizing enrichment cultures. Microbial activity accelerated the release of sulfate across all conditions. 16S rRNA gene sequencing and metagenomic analysis revealed the dominance of a putative chemolithoautotrophic sulfur-oxidizing bacterium from the genus Thiobacillus in the enrichment cultures. Previously proposed models for aerobic microbial pyrite oxidation were assessed in terms of physical constraints, enrichment culture geochemistry, and metagenomic analysis. Although we conclude that subsurface pyrite oxidation at SSCHZO is largely abiotic, this work nonetheless yields new insight into the potential pathways by which aerobic microorganisms may accelerate pyrite oxidation at circumneutral pH. We propose a new "direct sulfur oxidation" pathway, whereby sulfhydryl-bearing outer membrane proteins mediate oxidation of pyrite surfaces through a persulfide intermediate, analogous to previously proposed mechanisms for direct microbial oxidation of elemental sulfur. The action of this and other direct microbial pyrite oxidation pathways have major implications for controls on pyrite weathering rates in circumneutral pH sedimentary environments where pore throat sizes permit widespread access of microorganisms to pyrite surfaces.

Enhancement mechanism of polyoxyethylene nonyl phenyl ether on the bioleaching of chalcopyrite

Chalcopyrite is the most abundant copper-bearing mineral in nature. Due to technological limitations, a large amount of low-grade chalcopyrite is discarded, which causes a large waste of resources and a series of environmental problems. Bioleaching is a low-consumption technology that plays an important role in treating low-grade minerals. However, the leaching efficiency of chalcopyrite is too low for industrial production. This study proposes the use of polyoxyethylene nonyl phenyl ether (NP-15) to improve the bioleaching efficiency of chalcopyrite. The effects of concentration and adding time of NP-15 on copper extraction were investigated. After 30 days bioleaching, the copper concentration in the leaching solution was 930.91 mg/L with the addition of 20 mg/L of NP-15. In contrast, the copper concentration was observed to be 385.62 mg/L in the absence of NP-15. The optimum adding time was the 6th day after the start of the bioleaching process. The analysis of the results of X-ray diffraction (XRD), Raman spectroscopy, and the electrochemical tests revealed that the presence of NP-15 was beneficial to reduce the deposition of elemental sulfur on the chalcopyrite surface. Moreover, NP-15 promoted the oxidation of elemental sulfur by Acidithiobacillus ferrooxidans. The contents of elemental sulfur and polysulfide in the passivation layer were reduced. Additionally, NP-15 reduced the surface tension of the leaching solution, which was beneficial for improving the contact between the leaching solution and chalcopyrite surface. Thus, the bioleaching efficiency was improved. This study provides a reference for the application of surfactants to enhance the bioleaching of chalcopyrite ores.

Microbial selenate detoxification linked to elemental sulfur oxidation: Independent and synergic pathways

Elevated selenium levels in the environment, with soluble selenate [Se(VI)] as the common chemical species, pose a severe threat to human health. Anaerobic Se(VI) bioreduction is a promising approach for selenium detoxification, and various organic/inorganic electron donors have proved effective in supporting this bioprocess. Nevertheless, autotrophic Se(VI) bioreduction driven by solid inorganic electron donors is still not fully understood. This work is the first to employ elemental sulfur [S(0)] as electron donor to support Se(VI) bioreduction. A batch trial with mixed culture demonstrated the feasibility of this bioprocess, with Se(VI) removal efficiency of 92.4 ± 0.7% at an initial Se(VI) concentration of 10 mg/L within 36 h. Continuous column tests showed that increased initial concentration, flow rate, and introduction of NO3--N depressed Se(VI) removal. Se(VI) was mainly bioreduced to solid elemental Se with trace selenite in the effluent, while S(0) was oxidized to SO42-. Enrichment of Thiobacillus, Desulfurivibrio, and Sulfuricurvum combined with upregulation of genes serA, tatC, and soxB indicated Se(VI) bioreduction was coupled to S(0) oxidation. Thiobacillus performed S(0) oxidation and Se(VI) reduction independently. Intermediate metabolites as volatile fatty acids, hydrogen and methane from S(0) oxidation were utilized by heterotrophic Se(VI) reducers for Se(VI) detoxification, indicative of microbial synergy.

Investigating Soil Acidity Associated with Elemental Sulphur Oxidation and Nitrification Process on Soils under Cashew Tree, Southern Tanzania

Abstract

Anaerobic Neutrophilic Pyrite Oxidation by a Chemolithoautotrophic Nitrate-Reducing Iron(II)-Oxidizing Culture Enriched from a Fractured Aquifer.

Neutrophilic microbial pyrite (FeS2) oxidation coupled to denitrification is thought to be an important natural nitrate attenuation pathway in nitrate-contaminated aquifers. However, the poor solubility of pyrite raises questions about its bioavailability and the mechanisms underlying its oxidation. Here, we investigated direct microbial pyrite oxidation by a neutrophilic chemolithoautotrophic nitrate-reducing Fe(II)-oxidizing culture enriched from a pyrite-rich aquifer. We used pyrite with natural abundance (NA) of Fe isotopes (NAFe-pyrite) and 57Fe-labeled siderite to evaluate whether the oxidation of the more soluble Fe(II)-carbonate (FeCO3) can indirectly drive abiotic pyrite oxidation. Our results showed that in setups where only pyrite was incubated with bacteria, direct microbial pyrite oxidation contributed ca. 26% to overall nitrate reduction. The rest was attributed to the oxidation of elemental sulfur (S0), present as a residue from pyrite synthesis. Pyrite oxidation was evidenced in the NAFe-pyrite/57Fe-siderite setups by maps of 56FeO and 32S obtained using a combination of SEM with nanoscale secondary ion MS (NanoSIMS), which showed the presence of 56Fe(III) (oxyhydr)oxides that could solely originate from 56FeS2. Based on the fit of a reaction model to the geochemical data and the Fe-isotope distributions from NanoSIMS, we conclude that anaerobic oxidation of pyrite by our neutrophilic enrichment culture was mainly driven by direct enzymatic activity of the cells. The contribution of abiotic pyrite oxidation by Fe3+ appeared to be negligible in our experimental setup.

TREATMENT OF RECYCLED WATER OF OIL REFINERIES

This article provides a brief overview and characteristics of recycled and waste water of oil refineries, methods of their purification and disinfection. Chemical and biochemical processes involving sulfur and its compounds occurring in oil refining recycling systems were studied for further development of engineering solutions for water quality stabilization. It is established that elemental sulfur is the main starting material for the formation of sulfuric acid in the recycling system, which is the cause of an emergency. It is shown that the oxidation of elemental sulfur to sulfuric acid can occur both by chemical means and by means of microorganisms that oxidize sulfur.

Acidophilic Iron- and Sulfur-Oxidizing Bacteria, Acidithiobacillus ferrooxidans, Drives Alkaline pH Neutralization and Mineral Weathering in Fe Ore Tailings.

The neutralization of strongly alkaline pH conditions and acceleration of mineral weathering in alkaline Fe ore tailings have been identified as key prerequisites for eco-engineering tailings-soil formation for sustainable mine site rehabilitation. Acidithiobacillus ferrooxidans has great potential in neutralizing alkaline pH and accelerating primary mineral weathering in the tailings but little information is available. This study aimed to investigate the colonization of A. ferrooxidans in alkaline Fe ore tailings and its role in elemental sulfur (S0) oxidation, tailings neutralization, and Fe-bearing mineral weathering through a microcosm experiment. The effects of biological S0 oxidation on the weathering of alkaline Fe ore tailings were examined via various microspectroscopic analyses. It is found that (1) the A. ferrooxidans inoculum combined with the S0 amendment rapidly neutralized the alkaline Fe ore tailings; (2) A. ferrooxidans activities induced Fe-bearing primary mineral (e.g., biotite) weathering and secondary mineral (e.g., ferrihydrite and jarosite) formation; and (3) the association between bacterial cells and tailings minerals were likely facilitated by extracellular polymeric substances (EPS). The behavior and biogeochemical functionality of A. ferrooxidans in the tailings provide a fundamental basis for developing microbial-based technologies toward eco-engineering soil formation in Fe ore tailings.

Influence of Ferric Ions on the Electrochemical Dissolution Behaviors of Arsenopyrite in Sulfuric Acid of pH 1

ABSTRACT This study investigated the electrochemical oxidation behaviors of arsenopyrite in sulfuric acid (pH 1) containing various concentrations of ferric ions by cyclic voltammetry, Tafel polarization curves and electrochemical impedance spectra (EIS) measurements. Results indicated that the addition of ferric ions did not affect the electrochemical dissolution mechanism of arsenopyrite. With the increase of the ferric concentration, the corrosion potential of arsenopyrite shifted positively, and the corrosion current density increased. EIS tests showed that arsenopyrite oxidation consisted of two charge transfer processes, i.e., the release of iron and arsenic from arsenopyrite lattice and the oxidation of elemental sulfur formed on the arsenopyrite surface. The overall oxidation of arsenopyrite was controlled by the oxidation of elemental sulfur. The presence of ferric ions decreased the electron transfer resistances of both processes, contributing to the accelerated dissolution of arsenopyrite. Cyclic voltammetry and Tafel plots implied that the enhanced cathodic reaction was the dominant reason for the improved dissolution of arsenopyrite in the presence of ferric ions.

The oxygen isotopic signature of soil- and plant-derived sulphate is controlled by fertilizer type and water source.

The oxygen isotope signature of sulphate (δ18 Osulphate ) is increasingly used to study nutritional fluxes and sulphur transformation processes in a variety of natural environments. However, mechanisms controlling the δ18 Osulphate signature in soil-plant systems are largely unknown. The objective of this study was to determine key factors, which affect δ18 Osulphate values in soil and plants. The impact of an 18 O-water isotopic gradient and different types of fertilizers was investigated in a soil incubation study and a radish (Raphanus sativus L.) greenhouse growth experiment. Water provided 31-64% of oxygen atoms in soil sulphate formed via mineralization of organic residues (green and chicken manures) while 49% of oxygen atoms were derived from water during oxidation of elemental sulphur. In contrast, δ18 Osulphate values of synthetic fertilizer were not affected by soil water. Correlations between soil and plant δ18 Osulphate values were controlled by water δ18 O values and fertilizer treatments. Additionally, plant δ34 S data showed that the sulphate isotopic composition of plants is a function of S assimilation. This study documents the potential of using compound-specific isotope ratio analysis for investigating and tracing fertilization strategies in agricultural and environmental studies.

Evaluating the Potential of Halothiobacillus Bacteria for Sulfur Oxidation and Biomass Production under Saline Soil

Salinity negatively affects growth of sulfur-oxidizing bacteria (SOB) and their sulfate production ability, meanwhile decreases the available sulfate for plants in soil. The aim of this study was to isolate and characterize the bacteria of genus Halothiobacillus, as a salt-tolerant SOB, from saline and sulfidic habitats of Iran for the first time and evaluating the effect of salinity on their biomass and sulfate production during the oxidation of different sulfur sources. Isolation process and surveying the morphological, biochemical and 16S rRNA gene analysis resulted into identification of three species (eight strains) of Halothiobacillus genus including H. neapolitanus, H. hydrothermalis and H. halophilus. Salinity (0, 0.5, 1, 2 and 4 M NaCl) had a significant impact (p ≤ 0.01) on bacterial biomass and sulfate production during the oxidation of thiosulfate and elemental sulfur. Biomass and sulfate production by strains was accompanied by a decrease in residual content of thiosulfate (RCT) in medium. The amount of produced biomass and sulfate in medium supplemented by thiosulfate was much higher than elemental sulfur. The highest amount of biomass and sulfate was produced by H. neapolitanus strain I19 at 0.5 and 1 M NaCl concentration. The results of this study could be the first step to focus on the application of these bacteria to increase sulfate storage of saline soils and crop production.

Woodchip-sulfur packed biological permeable reactive barrier for mixotrophic vanadium (V) detoxification in groundwater

Groundwater vanadium (V) (V(V)) contamination is ubiquitous in vanadium mining/smelting region and development of novel strategy for its remediation is of particular significance. Herein woodchip-sulfur packed biological permeable reactive barrier (bio-PRB) is established towards successful V(V) bio-detoxification. V(V) removal was accelerated under such mixotrophic condition, compared with heterotrophic and autotrophic V(V) reductions. The performance of bio-PRB was relatively steady with V(V) removal efficiency of 68.5%–98.2% under fluctuant geochemical and hydrodynamic conditions. Microbial community analysis indicated that heterotrophic Geobacter was the main reducer to convert V(V) to insoluble V(IV), by consumption of organic source attributed to woodchip hydrolysis and sulfur anabolism of autotrophs (e.g., Sulfuricurvum and Thiobacillus). V(V) reduction and elemental sulfur oxidation were regulated by genes as omcA, omcB and mtrC and soxB, respectively. The elevated contents of cytochrome c and nicotinamide adenine dinucleotide implied that improved electron transfer facilitated V(V) reduction. This study provides a cost-effective, robust and sustainable route for V(V)-polluted aquifer remediation.

Electron distribution in sulfur-driven autotrophic denitrification under different electron donor and acceptor feeding schemes

Sulfur-driven autotrophic denitrification (SdAD) represents an effective alternative to heterotrophic denitrification process for the treatment of organic carbon deficient or organic carbon free water and wastewater streams. The electron supply by oxidation of sulfur substrates (i.e., total dissolved sulfide (TDS) and chemical elemental sulfur (S0chem)) and the electron distribution among nitrogen oxide reductases determines the denitrification rate, reduction and accumulation of intermediates (e.g., nitrite and nitrous oxide). In this study, the electron distribution (supply and consumption) in SdAD process was investigated through a series of batch experiments under electron donor and acceptor non-limiting and limiting feeding conditions. The electron distribution was significantly affected by sulfide loading rate, and the electron competition among nitrogen oxide reductases was intensified with the most electrons flowing towards nitrate reductase (Nar), and the least electrons towards nitrous oxide reductase (Nos) under decreased sulfide loading rate. The intensification of electron competition associated with unbalanced electron supply and consumption rates is more directly responsible for intermediates accumulation in SdAD process. Compared to S0chem, TDS was the preferable electron donor as it resulted in the lowest accumulation of denitrifying intermediates in SdAD process. The findings of this study not only improve the understanding of underlying mechanisms of electron distribution and accumulation of denitrifying intermediates in SdAD process, but also form a basis for selection of ideal electron donor and feeding conditions in applying SdAD process for remediation of water, wastewater and gaseous streams containing nitrogen and/or sulfide.

Characteristics of an Iron-Reducing, Moderately Acidophilic Actinobacterium Isolated from Pyritic Mine Waste, and Its Potential Role in Mitigating Mineral Dissolution in Mineral Tailings Deposits.

Reactive pyritic mine tailings can be populated by chemolithotrophic prokaryotes that enhance the solubilities of many metals, though iron-reducing heterotrophic microorganisms can inhibit the environmental risk posed by tailings by promoting processes that are the reverse of those carried out by pyrite-oxidising autotrophic bacteria. A strain (IT2) of Curtobacterium ammoniigenes, a bacterium not previously identified as being associated with acidic mine wastes, was isolated from pyritic mine tailings and partially characterized. Strain IT2 was able to reduce ferric iron under anaerobic conditions, but was not found to catalyse the oxidation of ferrous iron or elemental (zero-valent) sulfur, and was an obligate heterotrophic. It metabolized monosaccharides and required small amounts of yeast extract for growth. Isolate IT2 is a mesophilic bacterium, with a temperature growth optimum of 30 °C and is moderately acidophilic, growing optimally at pH 4.0 and between pH 2.7 and 5.0. The isolate tolerated elevated concentrations of many transition metals, and was able to grow in the cell-free spent medium of the acidophilic autotroph Acidithiobacillus ferrooxidans, supporting the hypothesis that it can proliferate in acidic mine tailings. Its potential role in mitigating the production of acidic, metal-rich drainage waters from mine wastes is discussed.

Mechanism for the Bio-Oxidation and Decomposition of Pentlandite: Implication for Nickel Bioleaching at Elevated pH

This work investigated the effects of Fe3+, H+ and adsorbed leaching bacteria on the bioleaching of pentlandite. Collectively, an integrated model for the oxidation and decomposition of pentlandite was built to describe the behaviors of different components in a bioleaching system. Proton ions and ferric ions could promote the break and oxidation of Ni-S and Fe-S bonds. The iron-oxidizing microorganisms could regenerate ferric ions and maintain a high Eh value. The sulfur-oxidizing microorganisms showed significant importance in the oxidation of polysulfide and elemental sulfur. The atoms in pentlandite show different modification pathways during the bioleaching process: iron transformed through a (Ni,Fe)9S8 → Fe2+ → Fe3+ → KFe3(SO4)2(OH)6 pathway; nickel experienced a transformation of (Ni,Fe)9S8 → NiS → Ni2+; sulfur modified through the pathway of S2−/S22− → Sn2− → S0 → SO32− → SO42−. During bioleaching, a sulfur-rich layer and jarosite layer formed on the mineral surface, and the rise of pH value accelerated the process. However, no evidence for the inhibition of the layers was shown in the bioleaching of pentlandite at pH 3.00. This study provides a novel method for the extraction of nickel from pentlandite by bioleaching at elevated pH values.

Distinct Roles of Acidophiles in Complete Oxidation of High-Sulfur Ferric Leach Product of Zinc Sulfide Concentrate.

A two-step process, which involved ferric leaching with biologically generated solution and subsequent biooxidation with the microbial community, has been previously proposed for the processing of low-grade zinc sulfide concentrates. In this study, we carried out the process of complete biological oxidation of the product of ferric leaching of the zinc concentrate, which contained 9% of sphalerite, 5% of chalcopyrite, and 29.7% of elemental sulfur. After 21 days of biooxidation at 40 °C, sphalerite and chalcopyrite oxidation reached 99 and 69%, respectively, while the level of elemental sulfur oxidation was 97%. The biooxidation residue could be considered a waste product that is inert under aerobic conditions. The results of this study showed that zinc sulfide concentrate processing using a two-step treatment is efficient and promising. The microbial community, which developed during biooxidation, was dominated by Acidithiobacillus caldus, Leptospirillum ferriphilum, Ferroplasma acidiphilum, Sulfobacillus thermotolerans, S. thermosulfidooxidans, and Cuniculiplasma sp. At the same time, F. acidiphilum and A. caldus played crucial roles in the oxidation of sulfide minerals and elemental sulfur, respectively. The addition of L. ferriphilum to A. caldus during biooxidation of the ferric leach product proved to inhibit elemental sulfur oxidation.

Potential Application of Selected Sulfur-Oxidizing Bacteria and Different Sources of Sulfur in Plant Growth Promotion under Different Moisture Conditions

ABSTRACTThis study aimed to investigate the combined effect of native sulfur-oxidizing bacteria and different sources of sulfur on pH, electrical conductivity, sulfate content in soil, plant growth indices and sulfate uptake by maize under different moisture conditions. A native sulfur-oxidizing bacteria was isolated and identified based on phenotypic characteristics and 16s rDNA sequencing. In this regard, a factorial experiment was conducted in a completely randomized design including Thiobacillus bacteria, sulfur sources, moisture and incubation time as experiment’s factors with three replications. Bacteria in two levels (with and without bacterial isolate), sulfur in three forms (elemental sulfur, granular sulfur and without sulfur), and moisture content in three levels (100%, 75% and 50% of field capacity) were considered. Results obtained from incubation experiment showed that the treatments effect on pH changes, electrical conductivity and the amount of sulfate ion were significant in 1% level and the highest pH changes and sulfur oxidation was related to BS 100% field capacity (inoculated and fertilized with elemental sulfur) treatment in second week. About greenhouse experiment, application of 570 mg sulfur per kg in the form of elemental sulfur and bacterial inoculum significantly increased stem diameter, plant height, shoot weight and sulfate uptake by maize plant. Inoculation of Thiobacillus along with elemental sulfur increases the oxidation of elemental sulfur resulting in increased nutrients availability in soil, consequently increased plant growth.