Methylation and dealkykation of tin compounds by sulfate- and nitrate-reducing bacteria

Microcosm study reveals the microbial and environmental effects on tributyltin degradation in an estuarine sediment

Tributyltin (TBT) is one of the most harmful contaminants ever released into the aquatic environment. Despite being banned, it is still present at many locations throughout the world. Its degradation in sediment mainly occurs through microbial biodegradation, a process that remains unclear. This study therefore aimed at better understanding TBT biodegradation in estuarine sediment and the microbial community associated with it. Microcosm experiments were set up, embracing a range of environmental control parameters. Major community shifts were recorded, mainly attributed to the change in oxygen status. The highest percentage of degradation (36,8%) occurred at 4 °C in anaerobic conditions. These results are encouraging for the in-situ bioremediation of TBT contaminated muddy sediment in temperate ports worldwide. However, with TBT able to persist in the coastal environment for decades when undisturbed in anoxic sediment, further research is needed to fully understand the mechanisms that triggered this biodegradation observed in the microcosms.

Disentangling the growth curve of microbial culture

Many researchers have studied the population dynamics of microbe of microbes as a typical example of population dynamics. The Monod equation, which mainly focuses on the growth and stationary phases, is used when plotting a growth curve. However, the growth potential in the late stage of culture has been overlooked. Previous studies considered the direct degradation of products to the limiting substrate. In this study, we considered microbial growth during the stationary phase, which enables us to describe the dynamics precisely. The microbes were divided into two populations: one grew by consuming the limiting substrate and the other degraded the products by metabolism. According to the numerical analysis of our model, microbes may choose one of two strategies: one consumes substrates and expands quickly, and the other grows slowly while cleaning up the environment in which they thrive. Furthermore, we found three types of microbial growth depending on their ability to detect metabolite accumulation. Using experimentally measured data, this model can estimate the dynamics of cell density, the substrates, and the metabolites used. The model's disentangling of growth curves offers novel interpretive possibilities for culture system dynamics.

Arsenic removal in flue gas through anaerobic denitrification and sulfate reduction cocoupled arsenic oxidation

Arsenic in flue gas from municipal solid waste incineration can damage to human health and ecological environment. A sulfate-nitrate-reducing bioreactor (SNRBR) for flue gas arsenic removal was investigated. Arsenic removal efficiency attained 89.4%. An integrated metagenomic and metaproteomic investigation showed that three nitrate reductases (NapA, NapB and NarG), three sulfate reductases (Sat, AprAB and DsrAB), and arsenite oxidase (ArxA) regulated nitrate reduction, sulfate reduction and bacterial As(III)-oxidation, respectively. Citrobacter and Desulfobulbus could synthetically regulate the expression of arsenite-oxidizing gene, nitrate reductases and sulfate reducatases, which involved in As(III) oxidation, nitrate and sulfate reduction. A bacterial consortium containing Citrobacter, UG_Enterobacteriaceas, Desulfobulbus and Desulfovibrio could capable of simultaneously arsenic oxidation, sulfate reduction and denitrification. Anaerobic denitrification and sulfate reduction were cocoupled to arsenic oxidation. The biofilm was characterized by FTIR, XPS, XRD, EEM, and SEM. XRD and XPS spectra verified the formation of aarsenic species (As(V)) from flue gas As(III) conversion. Arsenic speciation in biofilms of SNRBR consisted of 77% residual arsenic, 15.9% organic matter-bound arsenic, and 4.3% strongly absorbed arsenic. Flue gas arsenic was bio-stabilized in the form of Fe-As-S and As-EPS through biodeposition, biosorption and biocomplexation. This provides a new way of flue gas arsenic removal using the sulfate-nitrate-reducing bioreactor.

A microcosm approach for evaluating the microbial nonylphenol and butyltin biodegradation and bacterial community shifts in co-contaminated bottom sediments from the Gulf of Finland, the Baltic Sea

Pollution of aquatic ecosystems with nonylphenol (NP) and butyltins (BuTs) is of great concern due to their effects on endocrine activity, toxicity to aquatic organisms, and extended persistence in sediments. The impact of contamination with NP and/or BuTs on the microbial community structure in marine sediments was investigated using microcosms and high-throughput sequencing. Sediment microcosms with NP (300 mg/kg) and/or BuTs (95 mg/kg) were constructed. Complete removal of monobutyltin (MBT) occurred in the microcosms after 240 days of incubation, while a residual NP rate was 40%. The content of toxic tributyltin (TBT) and dibutyltin (DBT) in the sediments did not change notably. Co-contamination of the sediments with NP and BuTs did not affect the processes of their degradation. The pollutants in the microcosms could have been biodegraded by autochthonous microorganisms. Significantly different and less diverse bacterial communities were observed in the contaminated sediments compared to non-contaminated control. Firmicutes and Gammaproteobacteria dominated in the NP treatment, Actinobacteria and Alphaproteobacteria in the BuT treatment, and Gammaproteobacteria, Alphaproteobacteria, Firmicutes, and Acidobacteria in the NP-BuT mixture treatment. The prevalence of microorganisms from the bacterial genera Halothiobacillus, Geothrix, Methanosarcina, Dyella, Parvibaculum, Pseudomonas, Proteiniclasticum, and bacteria affiliated with the order Rhizobiales may indicate their role in biodegradation of NP and BuTs in the co-contaminated sediments. This study can provide some new insights towards NP and BuT biodegradation and microbial ecology in NP-BuT co-contaminated environment.

Confirmation of the systematic presence of tin particles in fallopian tubes or uterine horns of Essure implant explanted patients: A study of 18 cases with the same pathological process

OBJECTIVE

To examine associations between local and systemic symptoms and the wear of the tin weld of Essure implants.

DESIGN

study of a series of cases.

SETTINGS

Two French hospitals.

PARTICIPANTS

Eighteen patients explanted by hysterectomy and salpingectomy for removal of their Essure implants between September 2019 and July 2020, have had a common anatomopathological process.

MAIN OUTCOME MEASURES

anatomopathological examination by optical microscopy and mineralogical analysis of the fallopian tube or uterine horn with scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX). Evaluation of local and systemic symptoms with a questionnaire. Examination of blood metal assays (nickel, chromium, and tin).

RESULTS

anatomopathological examination highlights foreign body granulomas, fibrosis, adenomyosis, nonspecific inflammation, cysts and myomas in the Fallopian tubes, uterine horns, or both and mentions the presence of foreign bodies in seven cases. SEM-EDX analyses showed, systematically, the presence of tin particles integrated in the wall near the weld, generally in clusters, and with a size ranging from about one micron to several dozen microns. The questionnaire shows that the most frequent local symptoms were pelvic pain, urinary disorders, bleeding, and pains during intercourse. The most common systemic symptoms were: asthenia, visual disturbances, amnesia, giddiness, dorsal pains, headaches, and joint pains. The majority of local and systemic symptoms decreased after explantation, but sometimes incompletely. Before explantation, high levels of nickel, tin and chromium were observed in 11/17, 1/7 and 2/17 patients. After explantation, tin levels were high in 3/11 patients.

CONCLUSIONS

our new anatomopathological process systematically demonstrates the presence of tin particles in tissue near the weld. These particles could be responsible for granulomatous inflammations as well as local symptoms. Many of the systemic symptoms are consistent with chronic organotin poisoning but further studies are needed to find out whether tin from the solder can be converted to organotin in the patients' bodies.

Biological treatments of mercury and nitrogen oxides in flue gas: biochemical foundations, technological potentials, and recent advances

Nitrogen oxides (NO_x) and mercury (Hg) are commonly found coexistent pollutants in combustion flue gas. Ever-increasing emission of atmospheric Hg and NO_x has caused considerable environmental risks. Traditional flue gas demercuration and denitration techniques have many socioeconomic, technological and environmental drawbacks. Biotechnologies can be a promising and prospective alternative strategy. This article discusses theoretical foundation (biochemistry and genomic basis) and technical potentials (Hg⁰ bio-oxidation coupled to denitrification) of bioremoval of Hg and NO_x in flue gas and summarized recent experimental and technological advances. Finally, several specific technical perspectives have been put forward to better guide future researches.

Tin and mercury and their speciation (organotin compounds and methylmercury) in worldwide red wine samples determined by ICP-MS and GC-ICP-MS

One hundred and twenty-two red wines were analysed for their total tin, total mercury and speciation concentrations. Total Sn and Hg concentrations were in average 4.4 ± 7.2 µg/L and 0.22 ± 0.12 µg/L, respectively. Two GC-ICP-MS methods were developed and validated for speciation purposes: one to measure organotin compounds (OTCs) with internal standard correction; the other, to evaluate methylmercury (MeHg⁺) by isotopic dilution. Methyltins (mainly dimethyltin, but also monomethyltin) were the most abundant OTCs recovered. Methylation seems to occur biotically during the wine making process and not during the bottling time. Therefore, it also seems to be roughly dependent on the geographical origin of the wine. For higher OTCs, monobutyltin was the most regularly found, but dibutyltin and monooctyltin were also detected sometimes. MeHg⁺ was not recovered in any of the samples investigated, probably due to the low level of Hg. These results suggest that, in terms of these parameters, normal consumption of wine is not a hazard for human health.

Unusual tin organics, DDX and PAHs as specific pollutants from dockyard work in an industrialized port area in China

In order to recognize organic contaminants responsible for ecological stresses from intensive shipping traffic and dockyard works, this study aimed at characterizing the sediment contamination of a large industrialized port located in Hainan Island, China. Surface sediment samples were collected from 17 stations including the main docks, the dockyards and the major industrial wastewater outlets. Organotin compounds, the pesticide DDT (bis(chlorophenyl)trichloroethane) and its metabolites and polycyclic aromatic compounds were identified as main pollutant groups by GC/MS applying a non-target screening approach. The pesticide DDT and its metabolites were found in the same samples as the organotin derivatives pointing to similar emission sources. The concurrent presence of these compounds in the dockyard samples suggests a combined usage of organotin compounds and DDT as active ingredients in antifouling paints in Yangpu. As highly specific molecular indicators for dockyard activities, butyltin and phenyltin compounds were identified. Noteworthy, also tributylmethyltin and triphenylmethyltin were detected, likely resulting from microbial assisted biomethylation of synthetic organotin compounds in the sediments. The concentrations of PAHs, DDX and TBT in sediments from dockyards exceeded global sediment quality guidelines and the toxicity thresholds, and potentially have adverse biological effects on marine organisms.

On the effectiveness of tributyltin ban: Distribution and changes in butyltin concentrations over a 9-year period in Klaipėda Port, Lithuania

This study provides an insight on a long-term butyltin pressure, spatio-temporal changes and current tributyltin distribution in the Klaipėda Port sediments. Moreover, it examines whether the restrictions on tributyltin use led to a decreased pollution in the area. Changes over a 9-year period in tributyltin and its metabolites concentrations were analyzed in surface sediments from semi-enclosed bays of the Port. Reduction in organotin level was observed after tributyltin ban came into force: tributyltin concentration reached 3000 ng Sn g^-1 d.w. in 2005 whereas 1793 ng Sng^-1 d.w. was found to be the highest tributyltin concentration in 2013. The highest contamination was detected in the zones with ship maintenance activity. As late as in 2013, the latter areas still exhibited fresh tributyltin input while the progress of organotin degradation has been observed for other sampling stations along the Port.

Bio-oxidation of Elemental Mercury into Mercury Sulfide and Humic Acid-Bound Mercury by Sulfate Reduction for Hg0 Removal in Flue Gas

Bioconversion of elemental mercury (Hg⁰) into immobile, nontoxic, and less bioavailable species is of vital environmental significance. Here, we investigated bioconversion of Hg⁰ in a sulfate-reducing membrane biofilm reactor (MBfR). The MBfR achieved effective Hg⁰ removal by sulfate bioreduction. 16 S rDNA sequencing and metagenomic sequencing revealed that diverse groups of mercury-oxidizing/sulfate-reducing bacteria (Desulfobulbus, Desulfuromonas, Desulfomicrobium, etc.) utilized Hg⁰ as the initial electron donor and sulfate as the terminal electron acceptor to form the overall redox. These microorganisms coupled Hg⁰ bio-oxidation to sulfate bioreduction. Analysis on mercury speciation in biofilm by sequential extraction processes (SEPs) and inductively coupled mass spectrometry (ICP-MS) and by mercury temperature programmed desorption (Hg-TPD) showed that mercury sulfide (HgS) and humic acid-bound mercury (HA-Hg) were two major products of Hg⁰ bio-oxidation. With HgS and HA-Hg comprehensively characterized by X-ray diffraction (XRD), excitation-emission matrix spectra (EEM), scanning electron microscopy-energy disperse spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR), it was proposed that biologically oxidized mercury (Hg²⁺) further reacted with biogenic sulfides to form cubically crystallized metacinnabar (β-HgS) extracellular particles. Hg²⁺ was also complexed with functional groups -SH, -OH, -NH^-, and -COO^- in humic acids from extracellular polymeric substances (EPS) to form HA-Hg. HA-Hg may further react with biogenic sulfides to form HgS. Bioconversion of Hg⁰ into HgS was therefore achieved and can be a feasible biotechnique for flue gas demercuration.

Persistence times of refractory materials in landfills: A review of rate limiting conditions by mass transfer and reaction kinetics

Monitoring programs at closed landfills show that transformation of plastics, wood, and metals continue long after the active decomposition of the waste fractions are considered as complete. Studies conducted in natural anaerobic environments (e.g., marine sediments and rocks) provide insight for slow degradation mechanisms involving coupling of thermodynamically favorable and unfavorable reactions and biochemical transformations by microbial consortia. These transformations occur at much slower rates through more complex and less obvious mechanisms and are not evident until after the primary decomposition mechanisms become less significant. This study presents a review of the conditions that limit the mass transfer and reaction kinetics for anaerobic transformations in landfills and provides new insights for reaction mechanisms (e.g., anaerobic oxidation and anaerobic corrosion) that occur at relatively slow rates in mature landfills. Conditions and mechanisms of slow transformations by microbial and chemical activities with relatively small energy yields and availability of electron acceptors (e.g., inorganics, plastics) and/or diffusion of gas and moisture into the previously isolated areas in waste deposits were discussed. Time scales for mass transfer and reaction kinetics were compared under anaerobic conditions for different waste components deposited at municipal solid waste landfills. Half-lives of different materials under anaerobic conditions were estimated and compared. Emergence of syntrophic methanogenic communities and conditions for triboelectric effects were evaluated as possible electron transfer mechanisms between waste layers for occurrence of extremely slow transformations of wastes deposited in landfills.