Reducing Bacteria Activity Research Articles

Review of bacterial sulfate reduction in lacustrine deposition and its identification in the Jimsar Sag, Junggar Basin

Bacterial sulfate reduction (BSR) is the interaction between sulfates and organic matter that bacteria participate in during the early diagenetic stage. It is one of the important biogeochemical processes that affect the formation of sulfides and sulfur cycling. Due to the lack of sulfate in the lakes, there is relatively little research on lacustrine bacterial sulfate reduction (LBSR), and related research mainly focuses on marine sedimentation. Marine incursion and volcanic ash may bring sulfate to lakes, providing a possibility for the occurrence of LBSR. The process, main influencing factors, and identification methods of BSR are summarized systematically. Through comprehensive analysis, it is believed that the occurrence depth of LBSR is relatively shallow (about 10 cm). Sulfate concentration, total organic matter, and sulfate reducing bacteria activity are the main controlling factors of BSR. The petrological and geochemical characteristics of the product are commonly used indicators to determine whether BSR occurs. The Jimsar Sag is one of the important shale oil rich areas in China. Taking Jimsar Sag as an example, the identification of LBSR was attempted. Based on the characteristics of framboidal pyrite, columnar calcite, and fine-grained dolomite, comprehensive analysis suggests that LBSR has occurred in the Lucaogou Formation of the Jimsar Sag. BSR has a significant effect on the degradation of organic matter, and TOC is usually lower in areas with higher intensity. Therefore, BSR has impact on the enrichment of organic matter in shale. The relevant research may have reference significance for the enrichment of lacustrine organic matter and shale oil exploration.

Pengaruh Nitrat terhadap Biokorosi Logam oleh Konsorsium Bakteri Pereduksi Sulfat dari PLTA Saguling

<div><strong>The Influence of Nitrate in Metal Biocorrosion caused by Sulfate Reducing Bacteria from Saguling Hydropower</strong>. The corrosion facilitated and accelerated by the activities of microorganism is called biocorrosion. Sulfate reducing bacteria (SRB) is known as the bacteria that cause biocorrosion in anaerobic condition by using sulfate as the final electron acceptor. Biocorrosion reduces equipment lifetime and increases maintenance cost in industry. In the cooling system in Saguling hydropower, corrosion was commonly caused by utilization of contaminated water due to anorganic and organic waste, especially sulfate. In this research, sulfate reducing bacteria was isolated from biofilms in the cooling system of Saguling Hydropower. Molecular analysis using PCR-DGGE method with dsrB gene (350 bp) as molecular markers showed that SRB consortium contained 12 bands and assumed as different species of SRB. SRB consortium was tested to determine its biocorrosion activity over metal material of ST37 (carbon steel) and SUS304 (stainless steel). The consortium then treated with 7 different nitrate concentrations to determine its effect against the sulfate reducing bacteria activity. SRB consortium caused higher corrosion to ST37 than SUS304L, with the corrosion rate of 0.07660 mm/year and 0.00265 mm/year, respectively. Concentration of 10 mM nitrate effectively inhibited corrosion rate on ST37 and caused the changes in sulfate reducing bacteria communities, indicated by the disappearance of 6 bands in DGGE profile</div>

THE STUDY OF THE ROLE OF BIOLOGICAL IRON SULFIDE COMPOSITES ON COPPER REMOVAL BY CHANGING GEOCHEMICAL FORMS

The growth of biological iron sulfide composites and their efficacy for changing the geochemical forms of copper in sediment have been investigated. The role of bacteria in copper removal was identified using copper concentrations in three forms extracted via three sequential extraction methods. Furthermore, bacterial community diversity was investigated between different treatments. Copper was transformed from the weak acidic extraction state to the reduction state and the oxidation state under the action of biological iron sulfide composites. The conversion rates of copper from the weak acidic extraction state to other states was up to 76.66% and the increasing rates of the reduction state was up to 177.85%. Higher dissolved oxygen does harm sulfate reducing bacteria and results in low removal efficiency of copper. It can be inferred that differences in the bacterial community structure resulted in differences between conversion rates and biological efficacy through the correlation between copper concentration and alpha diversity or beta diversity. Furthermore, bacterial 16S rRNA gene analysis showed that Proteobacteria, which sulfate reducing bacteria belong to, were predominant in the group with higher removal efficiency. The biological iron sulfide composites affected the removal efficiency of copper by increasing the sulfate reducing bacteria activity inside the sediments

Dual effective core-shell electrospun scaffolds: Promoting osteoblast maturation and reducing bacteria activity

Herein, we electrospun ultrathin core-shell fibers based on polycaprolactone (PCL), polyethylene glycol (PEG), gelatin and osteogenic growth peptide (OGP), and evaluated their potential to upregulate human osteoblast cells (hFOB) and to reduce Gram-positive and Gram-negative bacteria. We also evaluated the fiber morphology, chemical structure and peptide delivery efficacy. The employment of core-shell fibers compared to fibers without a core-shell showed improved mechanical strength, comparable to the strength of pure PCL, as well as improved hydrophilicity and wettability. The careful selection of polymer combination and core-shell strategy promoted a controlled and sustained release of OGP. Moreover, increased calcium deposition (CD) (1.3-fold) and alkaline phosphate (ALP) activity was observed when hFOBs were cultivated onto core-shell fibers loaded with OGP after 21 days of culture. Our developed scaffolds were also able to reduce the amount of Pseudomonas aeruginosa (ATCC 25668) bacteria by a factor of two compared to raw PCL without the use of any antibiotics. All of these results demonstrate a promising potential of the developed core-shell electrospun scaffolds based on PCL:PEG:Gelatin:OGP for numerous bone tissue applications.

Anaerobic methane oxidation and aerobic methane production in an east African great lake (Lake Kivu)

We investigated CH4 oxidation in the water column of Lake Kivu, a deep meromictic tropical lake with CH4-rich anoxic deep waters. Depth profiles of dissolved gases (CH4 and N2O) and a diversity of potential electron acceptors for anaerobic CH4 oxidation (NO3−, SO42−, Fe and Mn oxides) were determined during six field campaigns between June 2011 and August 2014. Denitrification measurements based on stable isotope labelling experiments were performed twice. In addition, we quantified aerobic and anaerobic CH4 oxidation, NO3− and SO42− consumption rates, with and without the presence of an inhibitor of SO42−-reducing bacteria activity. Aerobic CH4 production was also measured in parallel incubations with the addition of an inhibitor of aerobic CH4 oxidation. The maximum aerobic and anaerobic CH4 oxidation rates were estimated to be 27 ± 2 and 16 ± 8 μmol/L/d, respectively. We observed a difference in the relative importance of aerobic and anaerobic CH4 oxidation during the rainy and the dry season, with a greater role for aerobic oxidation during the dry season. Lower anaerobic CH4 oxidation rates were measured in presence of molybdate in half of the measurements, suggesting the occurrence of linkage between SO42− reduction and anaerobic CH4 oxidation. NO3− consumption and dissolved Mn production rates were never high enough to sustain the measured anaerobic CH4 oxidation, reinforcing the idea of a coupling between SO42− reduction and CH4 oxidation in the anoxic waters of Lake Kivu. Finally, significant rates (up to 0.37 μmol/L/d) of pelagic CH4 production were also measured in oxygenated waters.

Evaluation of mercury biogeochemical cycling at the sediment–water interface in anthropogenically modified lagoon environments

The Marano and Grado Lagoon is well known for being contaminated by mercury (Hg) from the Idrija mine (Slovenia) and the decommissioned chlor-alkali plant of Torviscosa (Italy). Experimental activities were conducted in a local fish farm to understand Hg cycling at the sediment–water interface. Both diffusive and benthic fluxes were estimated in terms of chemical and physical features. Mercury concentration in sediments (up to 6.81μg/g) showed a slight variability with depth, whereas the highest methylmercury (MeHg) values (up to 10ng/g) were detected in the first centimetres. MeHg seems to be produced and stored in the 2–3cm below the sediment–water interface, where sulphate reducing bacteria activity occurs and hypoxic–anoxic conditions become persistent for days. DMeHg in porewaters varied seasonally (from 0.1 and 17% of dissolved Hg (DHg)) with the highest concentrations in summer. DHg diffusive effluxes higher (up to 444ng/m2/day) than those reported in the open lagoon (~95ng/m2/day), whereas DMeHg showed influxes in the fish farm (up to −156ng/m2/day). The diurnal DHg and DMeHg benthic fluxes were found to be higher than the highest summer values previously reported for the natural lagoon environment. Bottom sediments, especially in anoxic conditions, seem to be a significant source of MeHg in the water column where it eventually accumulates. However, net fluxes considering the daily trend of DHg and DMeHg, indicated possible DMeHg degradation processes. Enhancing water dynamics in the fish farm could mitigate environmental conditions suitable for Hg methylation.

Effects of Microbial Activities on Mercury Methylation in Farmland near Mercury Mining Area

In order to study the main effect of microbial activities on mercury(Hg) methylation in farmland, mercury contaminated upland soils and paddy soils near Hg mining area were sampled as experimental soils. Four treatments were designed including only sterilization as the control, accelerating the activities of sulfate reducing bacteria(SRB), inhibiting the SRB's activities, and accelerating the activities of iron-reducing bacteria(FeRB), to know the effects of microbial and non-microbial factors on mercury methylation in soils. The results were as follows:the highest concentration of methylmercury(MeHg) was observed in soils with SRB accelerated treatment, and the increments of MeHg concentrations in upland soils and paddy soils ranged from 0.15 μg·kg-1 to 0.38 μg·kg-1 and 1 μg·kg-1 to 2 μg·kg-1, respectively. Comparatively, little increments of MeHg concentration were seen in soils with SRB inhibited treatment and FeRB accelerated treatment, which were lower than 0.025 μg·kg-1. Compared with upland soils, more MeHg was formed in Paddy soils and the concentrations of MeHg in paddy soils were 4-9 times of that in upland soils. Variation in the number of SRB in soils was similar to that in the concentration of MeHg in soils, and the number of SRB was positively correlated with the concentration of MeHg concentrations in soils(R2=0.57,P<0.01). The above results indicated that activities of reducing bacteria, especially SRB, played key role in the methylation in soils. In addition, more attention should be paid to paddy soils due to the high potential of methylation when conducting any assessment and taking any measure to manage the health risk caused by the exposure to mercury.

Assessment of the performance of SMFCs in the bioremediation of PAHs in contaminated marine sediments under different redox conditions and analysis of the associated microbial communities

The biodegradation of naphthalene, 2-methylnaphthalene and phenanthrene was evaluated in marine sediment microbial fuel cells (SMFCs) under different biodegradation conditions, including sulfate reduction as a major biodegradation pathway, employment of anode as terminal electron acceptor (TEA) under inhibited sulfate reducing bacteria activity, and combined sulfate and anode usage as electron acceptors. A significant removal of naphthalene and 2-methylnaphthalene was observed at early stages of incubation in all treatments and was attributed to their high volatility. In the case of phenanthrene, a significant removal (93.83±1.68%) was measured in the closed circuit SMFCs with the anode acting as the main TEA and under combined anode and sulfate reduction conditions (88.51±1.3%). A much lower removal (40.37±3.24%) was achieved in the open circuit SMFCs operating with sulfate reduction as a major biodegradation pathway. Analysis of the anodic bacterial community using 16S rRNA gene pyrosequencing revealed the enrichment of genera with potential exoelectrogenic capability, namely Geoalkalibacter and Desulfuromonas, on the anode of the closed circuit SMFCs under inhibited SRB activity, while they were not detected on the anode of open circuit SMFCs. These results demonstrate the role of the anode in enhancing PAHs biodegradation in contaminated marine sediments and suggest a higher system efficiency in the absence of competition between microbial redox processes (under SRB inhibition), namely due to the anode enrichment with exoelectrogenic bacteria, which is a more energetically favorable mechanism for PAHs oxidation than sulfate.

The use of a passive treatment system for the mitigation of acid mine drainage at the Williams Brothers Mine (California): pilot-scale study

A pilot-scale study was undertaken to assess the feasibility of using a passive treatment system to mitigate the acid mine drainage at the abandoned Williams Brothers Mine site, a remote site located in Sierra National Forest (California). The advantages of implementing passive treatment systems in remote or abandoned mine sites are their low energy and maintenance requirements compared to conventional systems. A pilot-scale system was designed and implemented at the site, which consisted of: (1) an aeration rock channel to facilitate oxidation of ferrous iron to ferric iron; (2) a sedimentation tank to collect iron oxyhydroxide precipitates that could lead to the clogging of the system; (3) a peat biofilter for the removal of dissolved iron and copper; (4) a sulphate-reducing bacteria reactor for the generation of alkalinity and consequent pH increase, and the removal of dissolved nickel, zinc, and residual dissolved iron and copper; and, (5) a re-aeration limestone channel to add alkalinity prior to effluent discharge into the natural receiving environment. The pilot-scale system was monitored over a 17-month period (500 days from July 2007 to November 2008) and performance was determined by monitoring the pH, sulphate and dissolved metal concentrations of the influent acid mine drainage and the effluents from the peat biofilter and sulphate reducing bacteria reactor. A decrease in sulphate concentration was noted in the sulphate reducing bacteria reactor, suggesting sulphate reducing bacteria activity and alkalinity generation. The effluent pH from the system increased from as low as 4.5 to above 6.0, but remained below water quality objectives for the San Joaquin River Basin. Dissolved copper, nickel and zinc removal to below water quality objectives was noted in the peat biofilter to below water quality objectives. Dissolved iron and manganese removal was also observed in the sulphate reducing bacteria reactor. The feasibility of employing this system as a sustainable low cost and low maintenance treatment alternative at the Williams Brothers abandoned mine site to ensure that drainage effluent will meet water quality objectives showed promise. However, long-term monitoring would be required to demonstrate and ensure their long-term effectiveness.

Treatment of antimony mine drainage: challenges and opportunities with special emphasis on mineral adsorption and sulfate reducing bacteria.

The present article summarizes antimony mine distribution, antimony mine drainage generation and environmental impacts, and critically analyses the remediation approach with special emphasis on iron oxidizing bacteria and sulfate reducing bacteria. Most recent research focuses on readily available low-cost adsorbents, such as minerals, wastes, and biosorbents. It is found that iron oxides prepared by chemical methods present superior adsorption ability for Sb(III) and Sb(V). However, this process is more costly and iron oxide activity can be inhibited by plenty of sulfate in antimony mine drainage. In the presence of sulfate reducing bacteria, sulfate can be reduced to sulfide and form Sb(2)S(3) precipitates. However, dissolved oxygen and lack of nutrient source in antimony mine drainage inhibit sulfate reducing bacteria activity. Biogenetic iron oxide minerals from iron corrosion by iron-oxidizing bacteria may prove promising for antimony adsorption, while the micro-environment generated from iron corrosion by iron oxidizing bacteria may provide better growth conditions for symbiotic sulfate reducing bacteria. Finally, based on biogenetic iron oxide adsorption and sulfate reducing bacteria followed by precipitation, the paper suggests an alternative treatment for antimony mine drainage that deserves exploration.

Inhibiting sulfate reducing bacteria activity by denitrification in an anaerobic baffled reactor: influencing factors and mechanism analysis

For controlling the equipment corrosion of hydrogen sulfide produced by the microbe in oilfield system, denitrification was used to inhibit the sulfate reduction in a continuous flow anaerobic baffled reactor. The influencing factors and running effects of this process inhibition were investigated. Batch experiments were conducted to study the inhibitory mechanisms. The results indicated that SO42-/NO3- ratio and relative Chemical Oxygen Demand (COD) content were the two most important environmental factors affecting the inhibitory effect. The inhibitory effect increased with decrease of SO42-/NO3- ratio. The lower COD content benefited to increase the inhibitory effect. The inhibitor could act only in 1–3 chambers with the effective inhibitory time of 2.3–6.9 h. The inhibitory effect could be reflected by the system oxidation reduction potential (ORP). Denitrification predominated with the ORP in the range of −50 mV to −150 mV, while sulfate reduction predominated with the ORP in the range of −300 mV to −400 mV. Three inhibitory mechanisms were observed in the experiments: competitive inhibition for carbon source, nitrite-N inhibition, and oxidation by autotrophic denitrifying bacteria.

Treatment efficiency of acid mine drainage by the Ho-Nam Coal Mine passive treatment system

The Ho-nam coal mine passive treatment system, which consists of an oxidation pond, successive alkalinity producing system (SAPS) and aerobic wetland, was investigated to estimate the treatment efficiency of the entire system and each treatment step. After the acid mine drainage of Ho-nam coal mine moves through the entire system, metal concentration and acidity decreases and alkalinity increases. Acid mine drainage has been treated successfully by the Ho-nam coal mine passive treatment system. However, iron ions were not removed sufficiently in the oxidation pond even though ferrous ions oxidized to ferric ions. Furthermore, in SAPS, Fe concentration decreased rapidly but sulfate reducing bacteria activity was not shown in the system. These results suggest that the objectives of each step were not achieved as designed, although the system was found to be successful.

Antimicrobial applications of nanotechnology: methods and literature

The need for novel antibiotics comes from the relatively high incidence of bacterial infection and the growing resistance of bacteria to conventional antibiotics. Consequently, new methods for reducing bacteria activity (and associated infections) are badly needed. Nanotechnology, the use of materials with dimensions on the atomic or molecular scale, has become increasingly utilized for medical applications and is of great interest as an approach to killing or reducing the activity of numerous microorganisms. While some natural antibacterial materials, such as zinc and silver, possess greater antibacterial properties as particle size is reduced into the nanometer regime (due to the increased surface to volume ratio of a given mass of particles), the physical structure of a nanoparticle itself and the way in which it interacts with and penetrates into bacteria appears to also provide unique bactericidal mechanisms. A variety of techniques to evaluate bacteria viability, each with unique advantages and disadvantages, has been established and must be understood in order to determine the effectiveness of nanoparticles (diameter ≤100 nm) as antimicrobial agents. In addition to addressing those techniques, a review of select literature and a summary of bacteriostatic and bactericidal mechanisms are covered in this manuscript.