scholarly journals Biogeochemical factors affecting mercury methylation rate in two contaminated floodplain soils

2011 ◽  
Vol 8 (5) ◽  
pp. 8925-8959 ◽  
Author(s):  
T. Frohne ◽  
J. Rinklebe ◽  
U. Langer ◽  
G. Du Laing ◽  
S. Mothes ◽  
...  
Keyword(s):  
Sulfur Cycle ◽  
Mercury Species ◽  
Experimental Conditions ◽  
Factors Affecting ◽  
Sulfate Reducing ◽  
Floodplain Soils ◽  
Monomethyl Mercury ◽  
Reducing Bacteria ◽  
Plfa Analysis ◽  
Desulfovibrio Species

Abstract. An automated biogeochemical microcosm system allowing controlled variation of redox potential (EH) in soil suspensions was used to assess the effect of various factors on the mobility of mercury (Hg) as well as on the methylation of Hg in two contaminated floodplain soils with different Hg concentrations (approximately 5 mg kg−1 Hg and >30 mg kg−1 Hg). The experiment was conducted under stepwise variation from reducing (approximately −350 mV at pH 5) to oxidizing conditions (approximately 600 mV at pH 5). Results of phospholipid fatty acids (PLFA) analysis indicate the occurrence of sulfate reducing bacteria (SRB) such as Desulfobacter species (10me16:0, cy17:0, 10me18:0, cy19:0) or Desulfovibrio species (18:2ω6,9), which are considered to promote Hg methylation. The products of the methylation process are lipophilic, highly toxic methyl mercury species such as the monomethyl mercury ion [MeHg+], which is named as MeHg here. The ln(MeHg/Hgt) ratio is assumed to reflect the net production of monomethyl mercury normalized to total dissolved Hg (Hgt) concentration. This ratio increases with rising dissolved organic carbon (DOC) to Hgt ratio (lnDOC/lnHgt ratio) (R2 = 0.39, p < 0.0001, n = 63) whereas the relation between ln(MeHg/Hgt) ratio and lnDOC is weaker (R2 = 0.09; p < 0.05; n = 63). In conclusion, the DOC/Hgt ratio might be a more important factor for the Hg net methylation than DOC alone in the current study. Redox variations seem to affect the biogeochemical behavior of dissolved inorganic Hg species and MeHg indirectly through related changes in DOC, sulfur cycle, and microbial community structure whereas E,H and pH values, as well as concentration of dissolved Fe,3+/Fe2+ and Cl− seem to play subordinate roles in Hg mobilization and methylation under our experimental conditions.

scholarly journals Biogeochemical factors affecting mercury methylation rate in two contaminated floodplain soils

2012 ◽  
Vol 9 (1) ◽  
pp. 493-507 ◽  
Author(s):  
T. Frohne ◽  
J. Rinklebe ◽  
U. Langer ◽  
G. Du Laing ◽  
S. Mothes ◽  
...  
Keyword(s):  
Sulfur Cycle ◽  
Mercury Species ◽  
Experimental Conditions ◽  
Factors Affecting ◽  
Sulfate Reducing ◽  
Floodplain Soils ◽  
Monomethyl Mercury ◽  
Reducing Bacteria ◽  
Plfa Analysis ◽  
Desulfovibrio Species

Abstract. An automated biogeochemical microcosm system allowing controlled variation of redox potential (EH) in soil suspensions was used to assess the effect of various factors on the mobility of mercury (Hg) as well as on the methylation of Hg in two contaminated floodplain soils with different Hg concentrations (approximately 5 mg Hg kg−1 and >30 mg Hg kg–1). The experiment was conducted under stepwise variation from reducing (approximately −350 mV at pH 5) to oxidizing conditions (approximately 600 mV at pH 5). Results of phospholipid fatty acids (PLFA) analysis indicate the occurrence of sulfate reducing bacteria (SRB) such as Desulfobacter species (10Me16:0, cy17:0, 10Me18:0, cy19:0) or Desulfovibrio species (18:2ω6,9), which are considered to promote Hg methylation. The products of the methylation process are lipophilic, highly toxic methyl mercury species such as the monomethyl mercury ion [MeHg+], which is named as MeHg here. The ln(MeHg/Hgt) ratio is assumed to reflect the net production of monomethyl mercury normalized to total dissolved Hg (Hgt) concentration. This ratio increases with rising dissolved organic carbon (DOC) to Hgt ratio (ln(DOC/Hgt) ratio) (R2 = 0.39, p<0.0001, n= 63) whereas the relation between ln(MeHg/Hgt ratio and lnDOC is weaker (R2 = 0.09; p<0.05; n = 63). In conclusion, the DOC/Hgt ratio might be a more important factor for the Hg net methylation than DOC alone in the current study. Redox variations seem to affect the biogeochemical behavior of dissolved inorganic Hg species and MeHg indirectly through related changes in DOC, sulfur cycle, and microbial community structure whereas EH and pH values, as well as concentration of dissolved Fe3+/Fe2+ and Cl– seem to play subordinate roles in Hg mobilization and methylation under our experimental conditions.

scholarly journals A deep-sea sulfate reducing bacterium directs the formation of zero-valent sulfur via sulfide oxidation

2021 ◽  
Author(s):  
Rui Liu ◽  
Yeqi Shan ◽  
Shichuan Xi ◽  
Xin Zhang ◽  
Chaomin Sun
Keyword(s):  
Deep Sea ◽  
Sulfide Oxidation ◽  
Sulfur Cycle ◽  
Cold Seep ◽  
Cold Seeps ◽  
Protein Activity ◽  
Quinone Oxidoreductase ◽  
Sulfate Reducing ◽  
Thiosulfate Reductase ◽  
Reducing Bacteria

Zero-valent sulfur (ZVS) is a critical intermediate in the biogeochemical sulfur cycle. Up to date, sulfur oxidizing bacteria have been demonstrated to dominate the formation of ZVS. In contrast, formation of ZVS mediated by sulfate reducing bacteria (SRB) has been rarely reported. Here, we report for the first time that a typical sulfate reducing bacterium Desulfovibrio marinus CS1 directs the formation of ZVS via sulfide oxidation. In combination with proteomic analysis and protein activity assays, thiosulfate reductase (PhsA) and sulfide: quinone oxidoreductase (SQR) were demonstrated to play key roles in driving ZVS formation. In this process, PhsA catalyzed thiosulfate to form sulfide, which was then oxidized by SQR to form ZVS. Consistently, the expressions of PhsA and SQR were significantly up-regulated in strain CS1 when cultured in the deep-sea cold seep, strongly indicating strain CS1 might form ZVS in its real inhabiting niches. Notably, homologs of phsA and sqr widely distributed in the metagenomes of deep-sea SRB. Given the high abundance of SRB in cold seeps, it is reasonable to propose that SRB might greatly contribute to the formation of ZVS in the deep-sea environments. Our findings add a new aspect to the current understanding of the source of ZVS.

scholarly journals Formation of Biofilms and Biocorrosion on AISI-1020 Carbon Steel Exposed to Aqueous Systems Containing Different Concentrations of a Diesel/Biodiesel Mixture

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Ivanilda Ramos de Melo ◽  
Severino Leopoldino Urtiga Filho ◽  
Fernando Jorge Santos Oliveira ◽  
Francisca Pessoa de França
Keyword(s):  
Carbon Steel ◽  
Sulfate Reducing Bacteria ◽  
Experimental Conditions ◽  
Exposed Area ◽  
Sulfate Reducing ◽  
Corrosion Rates ◽  
Biodiesel Blend ◽  
Corrosion Pits ◽  
Reducing Bacteria ◽  
Significant Concentration

Environmental and economic concerns accelerated biofuels research and industrial production. Many countries have been using diesel and biodiesel blends as fuels justifying research on biofilms formation and metals corrosion. Cylinders made of AISI-1020 carbon steel with an exposed area of 1587 mm2, water, and water associated with B3 fuel (diesel/biodiesel blend at 97 : 3 v/v) were used.The formation of biofilms was detected, and biocorrosion was detected on AISI-1020. The results showed a variation in sessile microflora during the experiments. In the biofilms, a significant concentration of aerobic, anaerobic, IOB,Pseudomonas aeruginosa, and sulfate-reducing bacteria was observed. The corrosion rates varied between0.45±0.01and0.12±0.01 mm/year, depending on the experimental conditions. The main corrosion products identified were various forms of FeOOH, magnetite, and all forms of FexSy. In systems where there were high levels of sulfate reducing bacteria, corrosion pits were observed. In addition, the aliphatic hydrocarbons present in the fluid containing 10% B3 were totally degraded.

Symbiosis and competition among sulfate reduction, filamentous sulfur, denitrification, and poly-p accumulation bacteria in the anaerobic-oxic activated sludge of a municipal plant

1996 ◽  
Vol 34 (5-6) ◽  
pp. 119-128 ◽  
Author(s):  
Ryoko Yamamoto-Ikemoto ◽  
Saburo Matsui ◽  
Tomoaki Komori ◽  
E. J. Bosque-Hamilton
Keyword(s):  
Organic Acids ◽  
Activated Sludge ◽  
Sulfate Reduction ◽  
Sulfide Oxidation ◽  
Sulfate Reducing Bacteria ◽  
Sulfur Cycle ◽  
Sulfate Reducing ◽  
P Accumulation ◽  
Relationship Of ◽  
Reducing Bacteria

Symbiosis and competition were examined among sulfate reducing bacteria (SRB), filamentous sulfur bacteria (FSB), denitrification bacteria (DNB) and poly-P accumulation bacteria (PAB) in the activated sludge of a municipal plant operated under anaerobic-oxic conditions. Batch experiments were carried out using settled sewage from the same plant as the substrate under several conditions. Under oxic conditions, both sulfate reduction and sulfide oxidation occurred simultaneously, making a symbiotic relationship of SRB and FSB for establishment of a sulfur cycle sustaining the energy requirements. Under anoxic conditions, denitrification was dominant because DNB outcompeted PAB and SRB for organic acids. Under anaerobic conditions, phosphate release and sulfate reduction occurred simultaneously. SRB produced for moles of acetate from four moles of propionate and/or unknown substances by reduction of three moles of sulfate. PAB competed with sulfate-reducing bacteria for organic acids such as propionate. However, PAB utilized acetate produced by SRB.

scholarly journals Diversity, Activity, and Abundance of Sulfate-Reducing Bacteria in Saline and Hypersaline Soda Lakes

2007 ◽  
Vol 73 (7) ◽  
pp. 2093-2100 ◽  
Author(s):  
Mirjam Foti ◽  
Dimitry Y. Sorokin ◽  
Bart Lomans ◽  
Marc Mussman ◽  
Elena E. Zacharova ◽  
...  
Keyword(s):  
Denaturing Gradient Gel Electrophoresis ◽  
Soda Lakes ◽  
Reduction Rate ◽  
Sulfate Reducing Bacteria ◽  
Sulfur Cycle ◽  
Gene Copy ◽  
Sulfate Reduction Rate ◽  
Hypersaline Lake ◽  
Sulfate Reducing ◽  
Reducing Bacteria

ABSTRACT Soda lakes are naturally occurring highly alkaline and saline environments. Although the sulfur cycle is one of the most active element cycles in these lakes, little is known about the sulfate-reducing bacteria (SRB). In this study we investigated the diversity, activity, and abundance of SRB in sediment samples and enrichment cultures from a range of (hyper)saline soda lakes of the Kulunda Steppe in southeastern Siberia in Russia. For this purpose, a polyphasic approach was used, including denaturing gradient gel electrophoresis of dsr gene fragments, sulfate reduction rate measurements, serial dilutions, and quantitative real-time PCR (qPCR). Comparative sequence analysis revealed the presence of several novel clusters of SRB, mostly affiliated with members of the order Desulfovibrionales and family Desulfobacteraceae. We detected sulfate reducers and observed substantial sulfate reducing rates (between 12 and 423 μmol/dm3 day−1) for most lakes, even at a salinity of 475 g/liter. Enrichments were obtained at salt saturating conditions (4 M Na+), using H2 or volatile fatty acids as electron donors, and an extremely halophilic SRB, strain ASO3-1, was isolated. Furthermore, a high dsr gene copy number of 108 cells per ml was detected in a hypersaline lake by qPCR. Our results indicate the presence of diverse and active SRB communities in these extreme ecosystems.

scholarly journals Microbial Sulfur Cycle in Two Hydrothermal Chimneys on the Southwest Indian Ridge

mBio ◽  
2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Huiluo Cao ◽  
Yong Wang ◽  
On On Lee ◽  
Xiang Zeng ◽  
Zongze Shao ◽  
...  
Keyword(s):  
Microbial Community ◽  
Sulfur Oxidation ◽  
Sulfur Cycle ◽  
Southwest Indian Ridge ◽  
Sulfate Reducing ◽  
Sulfur Oxidizing ◽  
Indian Ridge ◽  
Midocean Ridge ◽  
Reducing Bacteria ◽  
Hydrothermal Fields

ABSTRACT Sulfur is an important element in sustaining microbial communities present in hydrothermal vents. Sulfur oxidation has been extensively studied due to its importance in chemosynthetic pathways in hydrothermal fields; however, less is known about sulfate reduction. Here, the metagenomes of hydrothermal chimneys located on the ultraslow-spreading Southwest Indian Ridge (SWIR) were pyrosequenced to elucidate the associated microbial sulfur cycle. A taxonomic summary of known genes revealed a few dominant bacteria that participated in the microbial sulfur cycle, particularly sulfate-reducing Deltaproteobacteria. The metagenomes studied contained highly abundant genes related to sulfur oxidation and reduction. Several carbon metabolic pathways, in particular the Calvin-Benson-Bassham pathway and the reductive tricarboxylic acid cycles for CO2 fixation, were identified in sulfur-oxidizing autotrophic bacteria. In contrast, highly abundant genes related to the oxidation of short-chain alkanes were grouped with sulfate-reducing bacteria, suggesting an important role for short-chain alkanes in the sulfur cycle. Furthermore, sulfur-oxidizing bacteria were associated with enrichment for genes involved in the denitrification pathway, while sulfate-reducing bacteria displayed enrichment for genes responsible for hydrogen utilization. In conclusion, this study provides insights regarding major microbial metabolic activities that are driven by the sulfur cycle in low-temperature hydrothermal chimneys present on an ultraslow midocean ridge. IMPORTANCE There have been limited studies on chimney sulfides located at ultraslow-spreading ridges. The analysis of metagenomes of hydrothermal chimneys on the ultraslow-spreading Southwest Indian Ridge suggests the presence of a microbial sulfur cycle. The sulfur cycle should be centralized within a microbial community that displays enrichment for sulfur metabolism-related genes. The present study elucidated a significant role of the microbial sulfur cycle in sustaining an entire microbial community in low-temperature hydrothermal chimneys on an ultraslow spreading midocean ridge, which has characteristics distinct from those of other types of hydrothermal fields.

Pyrite and the Global Environment

Pyrite ◽  
2015 ◽  
Author(s):  
David Rickard
Keyword(s):  
Iron Sulfide ◽  
Sulfide Oxidation ◽  
Sulfate Reducing Bacteria ◽  
Sulfide Mineral ◽  
Sulfur Cycle ◽  
Sulfate Reducing ◽  
Global Dynamic ◽  
Sulfur Oxidizing ◽  
Life On Earth ◽  
Reducing Bacteria

The two basic processes concerning pyrite in the environment are the formation of pyrite, which usually involves reduction of sulfate to sulfide, and the destruction of pyrite, which usually involves oxidation of sulfide to sulfate. On an ideal planet these two processes might be exactly balanced. But pyrite is buried in sediments sometimes for hundreds of millions of years, and the sulfur in this buried pyrite is removed from the system, so the balance is disturbed. The lack of balance between sulfide oxidation and sulfate reduction powers a global dynamic cycle for sulfur. This would be complex enough if this were the whole story. However, as we have seen, both the reduction and oxidation arms of the global cycle are essentially biological—specifically microbiological—processes. This means that there is an intrinsic link between the sulfur cycle and life on Earth. In this chapter, we examine the central role that pyrite plays, and has played, in determining the surface environment of the planet. In doing so we reveal how pyrite, the humble iron sulfide mineral, is a key component of maintaining and developing life on Earth. In Chapter 4 we concluded that Mother Nature must be particularly fond of pyrite framboids: a thousand billion of these microscopic raspberry-like spheres are formed in sediments every second. If we translate this into sulfur production, some 60 million tons of sulfur is buried as pyrite in sediments each year. But this is only a fraction of the total amount of sulfide produced every year by sulfate-reducing bacteria. In 1982 the Danish geomicrobiologist Bo Barker Jørgensen discovered that as much as 90% of the sulfide produced by sulfate-reducing bacteria was rapidly reoxidized by sulfur-oxidizing microorganisms. Sulfate-reducing microorganisms actually produce about 300 million tons of sulfur each year, but about 240 million tons is reoxidized. The magnitude of the sulfide production by sulfate-reducing bacte­ria can be appreciated by comparison with the sulfur produced by volcanoes. As discussed in Chapter 5, it was previously supposed that all sulfur, and thus pyrite, had a volcanic origin. In fact volcanoes produce just 10 million tons of sulfur each year.

Behavior of Microbiological Influenced Corrosion of the Ship Plate Steel in Marine Environment

2007 ◽  
Vol 348-349 ◽  
pp. 25-28
Author(s):  
Qing Fen Li ◽  
Chun Hui Li ◽  
Ping Long ◽  
Li Li Xue
Keyword(s):  
Marine Environment ◽  
Corrosion Potential ◽  
Electrochemical Impedance ◽  
Plate Steel ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
X Ray ◽  
Sulfate Reducing ◽  
Sterile Seawater ◽  
Reducing Bacteria

The microbiological influenced corrosion (MIC) behaviors of the ship plate steel directly exposed in different medias (the sterile seawater, the ferrous bacteria solution and the sulfate-reducing bacteria solution) were investigated with electrochemical impedance spectroscopy (EIS), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Corrosion potential, electrochemical impedance and micrographs of specimens under different experimental conditions were obtained. Results show that the FB and SRB in the marine environment affect the corrosion behavior of the ship plate steel greatly. The corrosion process in FB and SRB environment was controlled by both bacteria and corrosion products. The mechanism of MIC is discussed.

scholarly journals Analyses of Spatial Distributions of Sulfate-Reducing Bacteria and Their Activity in Aerobic Wastewater Biofilms

1999 ◽  
Vol 65 (11) ◽  
pp. 5107-5116 ◽  
Author(s):  
Satoshi Okabe ◽  
Tsukasa Itoh ◽  
Hisashi Satoh ◽  
Yoshimasa Watanabe
Keyword(s):  
In Situ Hybridization ◽  
Vertical Distribution ◽  
Reduction Rate ◽  
Sulfate Reducing Bacteria ◽  
Sulfur Cycle ◽  
Sulfate Reducing ◽  
High Sulfate ◽  
Reducing Bacteria ◽  
The Vertical Distribution

ABSTRACT The vertical distribution of sulfate-reducing bacteria (SRB) in aerobic wastewater biofilms grown on rotating disk reactors was investigated by fluorescent in situ hybridization (FISH) with 16S rRNA-targeted oligonucleotide probes. To correlate the vertical distribution of SRB populations with their activity, the microprofiles of O2, H2S, NO2 −, NO3 −, NH4 +, and pH were measured with microelectrodes. In addition, a cross-evaluation of the FISH and microelectrode analyses was performed by comparing them with culture-based approaches and biogeochemical measurements. In situ hybridization revealed that a relatively high abundance of the probe SRB385-stained cells (approximately 109 to 1010cells per cm3 of biofilm) were evenly distributed throughout the biofilm, even in the oxic surface. The probe SRB660-stained Desulfobulbus spp. were found to be numerically important members of SRB populations (approximately 108 to 109 cells per cm3). The result of microelectrode measurements showed that a high sulfate-reducing activity was found in a narrow anaerobic zone located about 150 to 300 μm below the biofilm surface and above which an intensive sulfide oxidation zone was found. The biogeochemical measurements showed that elemental sulfur (S0) was an important intermediate of the sulfide reoxidation in such thin wastewater biofilms (approximately 1,500 μm), which accounted for about 75% of the total S pool in the biofilm. The contribution of an internal Fe-sulfur cycle to the overall sulfur cycle in aerobic wastewater biofilms was insignificant (less than 1%) due to the relatively high sulfate reduction rate.

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