High Concentrations Of Perchlorate Research Articles

Effects of temperature, chloride and perchlorate salt concentration on the metabolic activity of Deinococcus radiodurans

The extremophile bacterium Deinococcus radiodurans is characterized by its ability to survive and sustain its activity at high levels of radiation and is considered an organism that might survive in extraterrestrial environments. In the present work, we studied the combined effects of temperature and chlorine-containing salts, with focus on perchlorate salts which have been detected at high concentrations in Martian regolith, on D. radiodurans activity (CO2 production rates) and viability after incubation in liquid cultures for up to 30 days. Reduced CO2 production capacity and viability was observed at high perchlorate concentrations (up to 10% w/v) during incubation at 0 or 25 °C. Both the metabolic activity and viability were reduced as the perchlorate and chloride salt concentration increased and temperature decreased, and an interactive effect of temperature and salt concentration on the metabolic activity was found. These results indicate the ability of D. radiodurans to remain metabolically active and survive in low temperature environments rich in perchlorate.

Metagenomic profiling of halites from the Atacama Desert: an extreme environment with natural perchlorate does not promote high diversity of perchlorate reducing microorganisms.

We surveyed the presence of perchlorate-reducing microorganisms in available metagenomic data of halite environments from the Atacama Desert, an extreme environment characterized by high perchlorate concentrations, intense ultraviolet radiation, saline and oxidizing soils, and severe desiccation. While the presence of perchlorate might suggest a broad community of perchlorate reducers or a high abundance of a dominant taxa, our search reveals a scarce presence. In fact, we identified only one halophilic species, Salinibacter sp003022435, carrying the pcrA and pcrC genes, represented in low abundance. Moreover, we also discovered some napA genes and organisms carrying the nitrate reductase nasB gene, which hints at the possibility of cryptic perchlorate reduction occurring in these ecosystems. Our findings contribute with the knowledge of perchlorate reduction metabolism potentially occurring in halites from Atacama Desert and point towards promising future research into the perchlorate-reducing mechanism in Salinibacter, a common halophilic bacterium found in hypersaline ecosystems, whose metabolic potential remains largely unknown.

Bioprospecting of extremophilic perchlorate-reducing bacteria: report of promising Bacillus spp. isolated from sediments of the bay of Cartagena, Colombia

Three extremophile bacterial strains (BBCOL-009, BBCOL-014 and BBCOL-015), capable of degrading high concentrations of perchlorate at a range of pH (6.5 to 10.0), were isolated from Colombian Caribbean Coast sediments. Morphological features included Gram negative strain bacilli with sizes averaged of 1.75 × 0.95, 2.32 × 0.65 and 3.08 × 0.70 μm, respectively. The reported strains tolerate a wide range of pH (6.5 to 10.0); concentrations of NaCl (3.5 to 7.5% w/v) and KClO4− (250 to 10000 mg/L), reduction of KClO4− from 10 to 25%. LB broth with NaCl (3.5–30% w/v) and KClO4ˉ (250-10000 mg/L) were used in independent trials to evaluate susceptibility to salinity and perchlorate, respectively. Isolates increased their biomass at 7.5 % (w/v) NaCl with optimal development at 3.5 % NaCl. Subsequently, ClO4ˉ reduction was assessed using LB medium with 3.5% NaCl and 10000 mg/L ClO4ˉ. BBCOL-009, BBCOL-014 and BBCOL-015 achieved 10%, 17%, and 25% reduction of ClO4ˉ, respectively. The 16 S rRNA gene sequence grouped them as Bacillus flexus T6186-2, Bacillus marisflavi TF-11 (T), and Bacillus vietnamensis 15 − 1 (T) respectively, with < 97.5% homology. In addition, antimicrobial resistance to ertapenem, vancomycine, amoxicillin clavulanate, penicillin, and erythromycin was present in all the isolates, indicating their high adaptability to stressful environments. The isolated strains from marine sediments in Cartagena Bay, Colombia are suitable candidates to reduce perchlorate contamination in different environments. Although the primary focus of the study of perchlorate-reducing and resistant bacteria is in the ecological and agricultural realms, from an astrobiological perspective, perchlorate-resistant bacteria serve as models for astrobiological investigations.

The effect of reflux ratio on sulfur disproportionation tendency in anaerobic baffled reactor with the heterotrophic combining sulfur autotrophic processes under high concentration perchlorate stress.

In a laboratory scale, an anaerobic baffled reactor (ABR) consisting of eight compartments, the heterotrophic combining sulfur autotrophic processes under different reflux ratios were constructed to achieve effective perchlorate removal and alleviate sulfur disproportionation reaction. Perchlorate was efficiently removed with effluent perchlorate concentration below 0.5 μg/L when the influent perchlorate concentration was 1030 mg/L during stages I ~ V, indicating that heterotrophic combining sulfur autotrophic perchlorate reduction processes can effectively achieve high concentration perchlorate removal. Furthermore, the 100% reflux ratio could reduce the contact time between sulfur particles and water; thus, the sulfur disproportionation reaction was inhibited. However, the inhibition effect of reflux on sulfur disproportionation was attenuated due to dilute perchlorate concentration when a reflux ratio of 150% and 200% was implemented. Meanwhile, the content of extracellular polymeric substances (EPS) in the heterotrophic unit (36.79 ~ 45.71 mg/g VSS) was higher than that in the sulfur autotrophic unit (22.19 ~ 25.77 mg/g VSS), indicating that high concentration perchlorate stress in the heterotrophic unit promoted EPS secretion. Thereinto, the PN content of sulfur autotrophic unit decreased in stage III and stage V due to decreasing perchlorate concentration in the autotrophic unit. Meanwhile, the PS content increased with increasing reflux in the autotrophic unit, which was conducive to the formation of biofilm. Furthermore, the high-throughput sequencing result showed that Proteobacteria, Chloroflexi, Firmicutes, and Bacteroidetes were the dominant phyla and Longilinea, Diaphorobacter, Acinetobacter, and Nitrobacter were the dominant genus in ABR, which were associated with heterotrophic or autotrophic perchlorate reduction and beneficial for effective perchlorate removal. The study indicated that reflux was a reasonable strategy for alleviating sulfur disproportionation in heterotrophic combining sulfur autotrophic perchlorate removal processes.

Bacterial model membranes under the harsh subsurface conditions of Mars.

Biomembranes are a key component of all living systems. Most research on membranes is restricted to ambient physiological conditions. However, the influence of extreme conditions, such as the deep subsurface on Earth or extraterrestrial environments, is less well understood. The deep subsurface of Mars is thought to harbour high concentrations of chaotropic salts in brines, yet we know little about how these conditions would influence the habitability of such environments. Here, we investigated the combined effects of high concentrations of Mars-relevant salts, including sodium and magnesium perchlorate and sulphate, and high hydrostatic pressure on the stability, structure, and function of a bacterial model membrane. To this end, several biophysical techniques have been employed, including calorimetry, fluorescence and CD spectroscopy, confocal microscopy, and small-angle X-ray scattering. We demonstrate that sulphate and perchlorate salts affect the properties of the membrane differently, depending on the counterion present (Na+vs. Mg2+). We found that the perchlorates, which are believed to be abundant salts in the Martian environment, induce a more hydrated and less ordered membrane, strongly favouring the physiologically relevant fluid-like phase of the membrane even under high-pressure stress. Moreover, we show that the activity of the phospholipase A2 is strongly modulated by both high pressure and salt. Compellingly, in the presence of the chaotropic perchlorate, the enzymatic reaction proceeded at a reasonable rate even in the presence of condensing Mg2+ and at high pressure, suggesting that bacterial membranes could still persist when challenged to function in such a highly stressed Martian environment.

The horizontal gene transfer of perchlorate reduction genomic island in three bacteria from an ecological niche.

Three new strains of dissimilatory perchlorate-reducing bacteria (DPRB), QD19-16, QD1-5, and P3-1, were isolated from an active sludge. Phylogenetic trees based on 16S rRNA genes indicated that QD19-16, QD1-5, and P3-1 belonged to Brucella, Acidovorax, and Citrobacter, respectively, expanding the distribution of DPRB in the Proteobacteria. The three strains were gram-negative and facultative anaerobes with rod-shaped cells without flagella, which were 1.0-1.6μm long and 0.5-0.6μm wide. The three DPRB strains utilized similar broad spectrum of electron donors and acceptors and demonstrated a similar capability to reduce perchlorate within 6days. The enzyme activity of perchlorate reductase in QD19-16 toward chlorate was higher than that toward perchlorate. The high sequence similarity of the perchlorate reductase operon and chlorite dismutase genes in the perchlorate reduction genomic islands (PRI) of the three strains implied that they were monophyletic origin from a common ancestral PRI. Two transposase genes (tnp1 and tnp2) were found in the PRIs of strain QD19-16 and QD1-5, but were absent in the strain P3-1 PRI. The presence of fragments of IR sequences in the P3-1 PRI suggested that P3-1 PRI had previously contained these two tnp genes. Therefore, it is plausible to suggest that a common ancestral PRI transferred across the strains Brucella sp. QD19-16, Acidovorax sp. QD1-5, and Citrobacter sp. P3-1 through horizontal gene transfer, facilitated by transposases. These results provided a direct evidence of horizontal gene transfer of PRI that could jump across phylogenetically unrelated bacteria through transposase. KEY POINTS: • Three new DPRB strains can effectively remove high concentration of perchlorate. • The PRIs of three DPRB strains are acquired from a single ancestral PRI. • PRIs are incorporated into different bacteria genome through HGT by transposase.

Perchlorate and chlorate assessment in drinking water in northern Chilean cities

Perchlorate and chlorate are endocrine disruptors considered emerging contaminants (ECs). Both oxyanions are commonly associated with anthropogenic contamination from fertilizers, pesticides, explosives, and disinfection byproducts. However, the soils of the Atacama Desert are the most extensive natural reservoirs of perchlorate in the world, compromising drinking water sources in northern Chile. Field campaigns were carried (2014–2018) to assess the presence of these ECs in the water supply networks of twelve Chilean cities. Additionally, the occurrence of perchlorate, chlorate and other anions typically observed in drinking water matrices of the Atacama Desert (i.e., nitrate, chloride, sulfate) was evaluated using a Spearman correlation analysis to determine predictors for perchlorate and chlorate. High concentrations of perchlorate (up to 114.48 μg L−1) and chlorate (up to 9650 μg L−1) were found in three northern cities. Spatial heterogeneities were observed in the physicochemical properties and anion concentrations of the water supply network. Spearman correlation analysis indicated that nitrate, chloride, and sulfate were not useful predictors for the presence of perchlorate and chlorate in drinking water in Chile. Hence, this study highlights the need to establish systematic monitoring, regulation, and treatment for these EC of drinking water sources in northern Chilean cities for public health protection.

Perchlorate reduction kinetics and genome-resolved metagenomics identify metabolic interactions in acclimated saline lake perchlorate-reducing consortia

Perchlorate is a widely detected environmental contaminant in surface and underground water, that seriously impacts human health by inhibiting the uptake of thyroidal radioiodine. Perchlorate reduction due to saline lake microorganisms is not as well understood as that in marine environments. In this study, we enriched a perchlorate-reducing microbial consortium collected from saline lake sediments and found that the perchlorate reduction kinetics of the enriched consortium fit the Michaelis–Menten kinetics well, with a maximum specific substrate reduction rate (qmax) of 0.596 ± 0.001 mg ClO4−/mg DW/h and half-saturation constant (Ks) of 16.549 ± 0.488 mg ClO4−/L. Furthermore, we used improved metagenome binning to reconstruct high-quality metagenome-assembled genomes from the metagenomes of the microbial consortia, including the perchlorate-reducing bacteria (PRB) Dechloromonas agitata and Wolinella succinogenes, with the genome of W. succinogenes harboring complete functional genes for perchlorate reduction being the first recovered. Given that the electrons were directly transferred to the electronic carrier cytochrome c-553 from the quinone pool, the electron transfer pathway of W. succinogenes was shorter and more efficient than the canonical pattern. This finding provides a theoretical basis for microbial remediation of sites contaminated by high concentrations of perchlorate. Metagenomic binning and metatranscriptomic analyses revealed the gene transcription variation of perchlorate reductase pcr and chlorite dismutase cld by PRB and the synergistic metabolic mechanism.

Impact of Acetate in Reduction of Perchlorate by Mixed Microbial Culture under the Influence of Nitrate and Sulfate.

The biological reduction of slow degradation contaminants such as perchlorate (ClO4−) is considered to be a promising water treatment technology. The process is based on the ability of a specific mixed microbial culture to use perchlorate as an electron acceptor in the absence of oxygen. In this study, batch experiments were conducted to investigate the effect of nitrate on perchlorate reduction, the kinetic parameters of the Monod equation and the optimal ratio of acetate to perchlorate for the perchlorate reducing bacterial consortium. The results of this study suggest that acclimated microbial cultures can be applied to treat wastewater containing high concentrations of perchlorate. Reactor experiments were carried out with different hydraulic retention times (HRTs) to determine the optimal operating conditions. A fixed optimal HRT and the effect of nitrate on perchlorate reduction were investigated with various concentrations of the electron donor. The results showed that perchlorate reduction occurred after nitrate removal. Moreover, the presence of sulfate in wastewater had no effect on the perchlorate reduction. However, it had little effect on biomass concentration in the presence of nitrate during exposure to a mixed microbial culture, considering the nitrate as the inhibitor of perchlorate reduction by reducing the degradation rate. The batch scale experiment results illustrated that for efficient operation of perchlorate reduction, the optimal acetate to perchlorate ratio of 1.4:1.0 would be enough. Moreover, these experiments found the following results: the kinetic parameters equivalent to Y = 0.281 mg biomass/mg perchlorate, Ks = 37.619 mg/L and qmax = 0.042 mg perchlorate/mg biomass/h. In addition, anoxic–aerobic experimental reactor results verify the optimal HRT of 6 h for continuous application. Furthermore, it also illustrated that using 600 mg/L of acetate as a carbon source is responsible for 100% of nitrate reduction with less than 50% of the perchlorate reduction, whereas at 1000 mg/L acetate, approximately 100% reduction was recorded.

Potassium perchlorate effects on primordial germ cells of developing medaka larvae

Perchlorate is a chemical compound commonly used in military artillery and equipment. It has been detected in drinking water, air, soil, and breast milk. Exposure of humans to perchlorate can occur in the theater of war and areas adjacent to military training grounds. A high concentration of perchlorate has been found to affect reproduction in vertebrates, including fish. However, whether environmental concentrations of perchlorate can affect primordial germ cells (PGCs), the founders of sperm and eggs, is not clearly understood. In the present study, we examined the effects of 0, 10, 100, and 1000 μg/L potassium perchlorate exposure on the embryonic development of medaka and their PGCs. Perchlorate exposure delayed hatching time, reduced heartbeat, inhibited migration of PGCs, and increased developmental deformities in the larvae. The 10 and 20 mg/L concentrations of perchlorate were lethal to embryos, whereas vitamin C co-treatment (1 mg/L) completely blocked perchlorate-induced mortality. RNA-seq analysis of isolated PGCs showed a non-linear pattern in expression profiles of differentially altered genes. Significantly upregulated genes were found in PGCs from the 10 and 1000 μg/L groups, whereas the 100 μg/L groups showed the highest number of significantly downregulated genes. Gene ontology analysis predicted differentially expressed genes to be involved in proteolysis, metabolic processes, peptides activity, hydrolase activity, and hormone activity. Among the cellular components, extracellular, intracellular, sarcoplasmic, and 6-phosphofructokinase and membrane-bounded processes were affected. Ingenuity Pathway Analysis of PGC transcriptomes revealed thyroid hormone signaling to be affected by all concentrations of perchlorate. The present results suggested that perchlorate affected the development of medaka larvae and vitamin C was able to ameliorate perchlorate-induced embryo mortality. Additionally, perchlorate altered the global transcriptional network in PGCs in a non-linear fashion suggesting its potential effects on developing germ cells and fertility.

Perchlorate-reducing bacteria from Antarctic marine sediments.

Perchlorate is a contaminant that can persist in groundwater and soil, and is frequently detected in different ecosystems at concentrations relevant to human health. This study isolated and characterised halotolerant bacteria that can potentially perform perchlorate reduction. Bacterial microorganisms were isolated from marine sediments on Deception, Horseshoe and Half Moon Islands of Antarctica. The results of the 16S ribosomal RNA (rRNA) gene sequence analysis indicated that the isolates were phylogenetically related to Psychrobacter cryohalolentis, Psychrobacter urativorans, Idiomarina loihiensis, Psychrobacter nivimaris, Sporosarcina aquimarina and Pseudomonas lactis. The isolates grew at a sodium chloride concentration of up to 30% and a perchlorate concentration of up to 10,000mg/L, which showed their ability to survive in saline conditions and high perchlorate concentrations. Between 21.6 and 40% of perchlorate was degraded by the isolated bacteria. P. cryohalolentis and P. urativorans degraded 30.3% and 32.6% of perchlorate, respectively. I. loihiensis degraded 40% of perchlorate, and P. nivimaris, S. aquimarina and P. lactis degraded 22%, 21.8% and 21.6% of perchlorate, respectively. I. loihiensis had the highest reduction in perchlorate, whereas P. lactis had the lowest reduction. This study is significant as it is the first finding of P. cryohalolentis and. P. lactis on the Antarctic continent. In conclusion, these bacteria isolated from marine sediments on Antarctica offer promising resources for the bioremediation of perchlorate contamination due to their ability to degrade perchlorate, showing their potential use as a biological system to reduce perchlorate in high-salinity ecosystems.

Perchlorate bioreduction in UASB reactor: S2--autotrophic granular sludge formation and sulphate generation control

ABSTRACT Perchlorate () industrial wastewater requires efficient removal to prevent adverse environmental impacts, however, high concentration and low biodegradability give rise to poor bioreduction performance. -autotrophic granular sludge (-AuGS) was firstly cultivated for high concentration perchlorate () removal in the upflow anaerobic sludge blanket (UASB) reactor (: 150 mg L−1). Simultaneously, the was utilized to control the generation as electron donor, the effluent concentration (190 mg L−1) was satisfied with drinking water standard (250 mg L−1). Under the optimized condition of hydraulic retention time (HRT) (6 h) and / molar ratio (2.2), more EPS was secreted, which promoted the -AuGS formation and stability. Though acclimation of 146 d, the -AuGS was formed with a large average granular sludge size (612 μm) and an excellent settleability (sludge volume index: SVI5/SVI30 = 1). With the mature -AuGS formation, the highest and loading was increased to 1.06 and 0.75 kg m−3 d−1. Interestingly, Georgfuchsia, Methyloversatilis, Sulfurisoma, and Exiguobacterium were the main microbial community in the -AuGS. This study proposed to form a novel -AuGS for developing the high concentration removal performance and to utilize the as an electron donor for controlling the excessive generation.

(Physical and Analytical Electrochemistry Division David C. Grahame Award) My 54 Years of Doing Electrochemistry and What Is New

I am very honored to be selected to receive the David C. Graham Award from the Electrochemical Society, an award that has been bestowed on so many outstanding electrochemists over the years including many of my mentors. This symposium is also close to my 70th birthday and may then be near the end of attending ECS meetings. My talk will start with an acknowledgement that awards like this do not happen without the students, post docs and colleagues that have worked for me and with me over my 54 years of doing electrochemistry that started with science fairs in high school and is ending at the University of Wyoming. Ironically the first papers that I read when arriving in graduate school at Caltech were David Graham’s pioneering work on double layers at mercury electrodes that were very relevant to part of my PhD work on double layer effects on electron transfer kinetics at mercury electrodes. My post doc at Bell Labs introduced me to solid state science and semiconductor photoelectrochemistry as applied to solar energy conversion. These topics continued to interest me for the rest of my career in photoelectrochemistry but I was always interested in learning new things and attacking interesting problems and I will briefly review some of this work. These include research in the areas of UHV surface science, both developing and applying scanning probe microscopies, growth and applications of 2D materials (long before they became a trend) and even photoelectrochemical processes on the surface of Mars where we explained the photoelectrochemical origin of the high concentrations of perchlorate on the surface of Mars.The rest of the talk will be concerned with an entirely new area for me, covalent organic framework (COF) materials applied to membranes applications, that has been a focus for the last few years. In this new project, a collaboration with colleagues at the University of Wyoming, involves developing two dimensional COFs with controllable sized hexagonal pores that we can functionalize with a wide variety of functional groups. We have been exploring applications of membranes constructed from these 2D-COFs for ion sieving based on size and charge, organic solvent separation and their antifouling abilities. Specifically, we have designed and tested a membrane constructed for a 2D-COF with pores that are lined with carboxylate groups that demonstrates a very specific size cut off for the conduction of a series of increasing sized tetraalkylammonium cations when paired with a polymeric anion that will not pass through the membrane. The stucture of this family of 2D-COFs is shown in the Figure. We have also demonstrated very high fluxes for organic solvent nanofiltration that is related to their polarity, size and hydrogen bonding properties. A future focus will be on developing a membrane that excludes small ions that will be useful in desalinization systems. Figure 1

The effect of step-feeding distribution ratio on high concentration perchlorate removal performance in ABR system with heterotrophic combined sulfur autotrophic process

In a lab-scale anaerobic baffled reactor (ABR) with eight compartments, the heterotrophic and sulfur autotrophic processes were combined to remove perchlorate. And then, the step-feeding distribution ratio of the heterotrophic perchlorate reduction unit (HPR unit) was optimized to achieve efficient removal of high concentration perchlorate. Under the optimized step-feeding distribution ratio, the perchlorate removal efficiency reached to 99.8% with the influent concentration of 1300 mg/L, indicating that the removal performance of step-feeding was better than that of normal-feeding. A mass balance results showed that the perchlorate removal capacity of the C1-C5 compartments were 11.8 ± 0.6, 13.2 ± 0.2, 11.7 ± 1.0, 8.8 ± 0.2 and 9.8 ± 1.0 g/d during the stage VIII, indicating that the step-feeding can effectively relieve pollutant loading of C1 compartment and improve the perchlorate removal capacity of the C2-C5 compartments. Moreover, the high-throughput sequencing analysis showed that bacterial community was significant difference between the HPR and sulfur autotrophic perchlorate removal (SAPR) units. Principal component analysis (PCA) showed that perchlorate removal was more positive correlation with the forward compartments than the posterior compartments of HPR unit. The study confirms that the optimized step-feeding ratio is beneficial to remove the high concentration perchlorate via combining heterotrophic and sulfur autotrophic processes.

Survival and growth of soil microbial communities under influence of sodium perchlorates

AbstractPreviously conducted space missions revealed the presence of perchlorates, which are known to have a high oxidizing potential in Martian regolith, at the level of 0.5%. Due to hygroscopic properties and crystallization features of perchlorate-containing solutions, assumptions leading to the possibility of the existence of liquid water in the form of brines, which can contribute to the vital activity of microorganisms, have been made. At the same time, high concentrations of perchlorates can inhibit the growth of microorganisms and cause their death. Previously performed studies have discovered the presence of highly diverse microbial communities in terrestrial perchlorate-containing soils and have also demonstrated the stability and activity of some prokaryotes cultured on highly concentrated perchlorates media (over 10%). Nevertheless, the limits of microbial tolerance to perchlorates and whether microbial communities are able to withstand the effects of high concentrations of perchlorates remain uncertain. The aim of this research was to study the reaction of microbial communities of hot-arid and cryo-arid soils and sedimentary rocks to the adding of a highly concentrated solution of sodium perchlorate (5%) in situ. An increase in the total number of prokaryotes, the number of metabolically active Bacteria and Archaea, and the variety of the consumed substrates were revealed. It was observed that in samples incubated with sodium perchlorate, a high taxonomic diversity of the microbial community is preserved at a level comparable to control sample. The study shows that the presence of high concentrations of sodium perchlorate (5%) in the soil does not lead to the death or significant inhibition of microbial communities.

High pressures increase \u03b1-chymotrypsin enzyme activity under perchlorate stress

Deep subsurface environments can harbour high concentrations of dissolved ions, yet we know little about how this shapes the conditions for life. We know even less about how the combined effects of high pressure influence the way in which ions constrain the possibilities for life. One such ion is perchlorate, which is found in extreme environments on Earth and pervasively on Mars. We investigated the interactions of high pressure and high perchlorate concentrations on enzymatic activity. We demonstrate that high pressures increase α-chymotrypsin enzyme activity even in the presence of high perchlorate concentrations. Perchlorate salts were shown to shift the folded α-chymotrypsin phase space to lower temperatures and pressures. The results presented here may suggest that high pressures increase the habitability of environments under perchlorate stress. Therefore, deep subsurface environments that combine these stressors, potentially including the subsurface of Mars, may be more habitable than previously thought.

Identification of a parasitic symbiosis between respiratory metabolisms in the biogeochemical chlorine cycle.

A key step in the chlorine cycle is the reduction of perchlorate (ClO4-) and chlorate (ClO3-) to chloride by microbial respiratory pathways. Perchlorate-reducing bacteria and chlorate-reducing bacteria differ in that the latter cannot use perchlorate, the most oxidized chlorine compound. However, a recent study identified a bacterium with the chlorate reduction pathway dominating a community provided only perchlorate. Here we confirm a metabolic interaction between perchlorate- and chlorate-reducing bacteria and define its mechanism. Perchlorate-reducing bacteria supported the growth of chlorate-reducing bacteria to up to 90% of total cells in communities and co-cultures. Chlorate-reducing bacteria required the gene for chlorate reductase to grow in co-culture with perchlorate-reducing bacteria, demonstrating that chlorate is responsible for the interaction, not the subsequent intermediates chlorite and oxygen. Modeling of the interaction suggested that cells specialized for chlorate reduction have a competitive advantage for consuming chlorate produced from perchlorate, especially at high concentrations of perchlorate, because perchlorate and chlorate compete for a single enzyme in perchlorate-reducing cells. We conclude that perchlorate-reducing bacteria inadvertently support large populations of chlorate-reducing bacteria in a parasitic relationship through the release of the intermediate chlorate. An implication of these findings is that undetected chlorate-reducing bacteria have likely negatively impacted efforts to bioremediate perchlorate pollution for decades.

Adsorption of high concentration perchlorate from aqueous solution onto Mg/Fe magnetic hydrotalcite calcined product (MAG@CHT): kinetics and isotherm study

Adsorption of high concentration perchlorate from aqueous solution onto Mg/Fe magnetic hydrotalcite calcined product (MAG@CHT): kinetics and isotherm study

Responses of microbial community to different concentration of perchlorate in the Qingyi River.

Perchlorate is a refractory and mobile contaminant that is wildly distributed in surface water, and due to its tremendous inhibitory effect on mammalian thyroid function, it has gained much attention in recent years. Numerous studies have focused on environmental detection of perchlorate, especially in water. However, less attention has been paid to the effects of perchlorate on the composition of the microbial community in rivers. Upstream of the Qingyi River, an important source of drinking water for local residents, there are two perchlorate manufacturers. In this study, we selected eight study sites from upstream to downstream of the Qingyi River, including sites located upstream and downstream of the perchlorate manufacturers. Our results indicated that perchlorate was detected in all sites except for QYR2, QYR3, and QYR10. The concentration of perchlorate in the five study sites was much higher than the reference dose proposed by the National Academy of Science, and ranged from 187 to 9647.00μg/L. We utilized 16S rDNA high throughput sequencing to analyze changes in the composition of the microbial community, based on the Illumina 2 × 250 MiSeq platform. The results showed that, when microbial communities were exposed to high concentration of perchlorate, there was an increase in the ratio of Betaproteobacteria, Bacteroidetes, Actinobacteria, and Saccharibacteria in the microbial community along with a decrease in the ratio of Chloroflexi, Verrucomicrobia, and Gammaproteobacteria. Our study has provided a theoretical basis for the alteration of the microbial community caused by the perchlorate pollution, which maybe have a truly important impact on the quality of groundwater.

Perchlorate in environmental waters of the Laurentian Great Lakes watershed: Evidence for uneven loading

Abstract A database of nearly 500 analyses of perchlorate in water samples from the Laurentian Great Lakes (LGL) watershed is presented, including samples from streams, from the Great Lakes and their connecting waters, with a special emphasis on Lake Erie. These data were assessed to test an earlier hypothesis that loading of perchlorate to the LGL watershed is relatively uniform. Higher perchlorate concentrations in streams in more developed and urban areas appear to indicate higher rates of loading from anthropogenic sources in these areas. Variable perchlorate concentrations in samples from Lake Erie indicate transient (un-mixed) conditions, and suggest loss by microbial degradation, focused in the central basin of that lake. Interpretation of the data included estimation of annual loading by streams in various sub-watersheds, and simulations (steady state and transient state) of the mass balance of perchlorate in the Great Lakes. The results suggest uneven loading from atmospheric deposition and other sources.