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Perchlorate is one of the major inorganic pollutants in the natural environment and the living environment, which is toxic to organisms and difficult to degrade due to its special structure. As previously reported, the Phoenix Mars lander detected approximately 0.6% perchlorate in the Martian soil, indicating challenges for Earth-based life to survive there. Currently, biological approaches using dissimilatory perchlorate-reducing bacteria (DPRB) are the most promising methods for perchlorate degradation. However, the majority of DPRB exhibit limited radiation resistance, rendering them unsuitable for survival on Mars. In this study, we obtained the transcriptome data of Deinococcus deserti , and predicted and identified multiple constitutive expression promoters of D . deserti with varying activities. The top-five most active promoters were separately fused to specific genes involved in the degradation of perchlorate from DPRB Dechloromonas agitata CKB, and transformed into Deinococcus radiodurans R1, forming a novel dissimilatory perchlorate-reducing bacterium, R1-CKB. It exhibited both efficient perchlorate degradation capability and strong radiation resistance, potentially offering a valuable tool for the further enhancement of the Martian atmosphere in the future.

Perchlorate (ClO 4 - ) mainly exists in the form of ammonium perchlorate in industrial production. However, the degradation mechanisms of different concentrations of ammonium nitrogen (NH 4 + -N) and ClO 4 - mixed pollutants in the environment are not well understood. This study aims to explore the potential of different types of carbon sources for ClO 4 - and NH 4 + -N biodegradation. Experimental results showed that the concentration and type of carbon sources are decisive to simultaneous removal of NH 4 + -N and ClO 4 - . Under condition of C(COD)/C(ClO 4 - ) ratio of 21.15 ± 4.40, the simultaneously removal efficiency of ClO 4 - and NH 4 + -N in acetate (Ace) was relatively higher than that in methanol (Met). C(NH 4 + -N)/C(ClO 4 - ) ratio of 9.66 ± 0.51 and C(COD)/C(ClO 4 - ) ratio of 2.51 ± 0.87 promoted ClO 4 - reduction in glucose-C (Glu-C). However, high concentration of Glu could cause pH decrease (from 7.57 to 4.59), thereby inhibiting ClO 4 - reduction. High-throughput sequencing results indicated that Proteobacteria and Bacteroidetes have made a major contribution to the simultaneous removal of NH 4 + -N and ClO 4 - . They are two representative bacterial phyla for participating in both ClO 4 - reduction and denitrification. Notably, the abundance of main ClO 4 - degrading bacteria (such as Proteobacteria, Chloroflexi, and Firmicutes) significantly increased by 528.57 % in Glu-C. It can be inferred that the concentration of carbon source and NH 4 + -N were the most important factors determining the removal efficiency of ClO 4 - by influencing changes in the core microbial community. This study will provide new techniques and mechanistic insights for the simultaneous removal of mixed ClO 4 - and nitrogen pollutants, which can also provide theoretical support for innovation in future biological treatment processes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

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 KClO 4 - (250 to 10000 mg/L), reduction of KClO 4 - from 10 to 25%. LB broth with NaCl (3.5-30% w/v) and KClO4- (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, ClO 4 - reduction was assessed using LB medium with 3.5% NaCl and 10000 mg/L ClO 4 -. BBCOL-009, BBCOL-014 and BBCOL-015 achieved 10%, 17%, and 25% reduction of ClO 4 -, 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., (© 2024. The Author(s).)

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 (CO 2 production rates) and viability after incubation in liquid cultures for up to 30 days. Reduced CO 2 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., (© 2024. The Author(s).)

Microbial reduction of perchlorate (ClO 4 - ) is emerging as a cost-effective strategy for groundwater remediation. However, the effectiveness of perchlorate reduction can be suppressed by the common co-contamination of nitrate (NO 3 - ). We propose a means to overcome the limitation of ClO 4 - reduction: depositing palladium nanoparticles (Pd 0 NPs) within the matrix of a hydrogenotrophic biofilm. Two H 2 -based membrane biofilm reactors (MBfRs) were operated in parallel in long-term continuous and batch modes: one system had only a biofilm (bio-MBfR), while the other incorporated biogenic Pd 0 NPs in the biofilm matrix (bioPd-MBfR). For long-term co-reduction, bioPd-MBfR had a distinct advantage of oxyanion reduction fluxes, and it particularly alleviated the competitive advantage of NO 3 - reduction over ClO 4 - reduction. Batch tests also demonstrated that bioPd-MBfR gave more rapid reduction rates for ClO 4 - and ClO 3 - compared to those of bio-MBfR. Both biofilm communities were dominated by bacteria known to be perchlorate and nitrate reducers. Functional-gene abundances reflecting the intracellular electron flow from H 2 to NADH to the reductases were supplanted by extracellular electron flow with the addition of Pd 0 NPs.

The Martian surface and shallow subsurface lacks stable liquid water, yet hygroscopic salts in the regolith may enable the transient formation of liquid brines. This study investigated the combined impact of water scarcity, UV exposure, and regolith depth on microbial survival under Mars-like environmental conditions. Both vegetative cells of Debaryomyces hansenii and Planococcus halocryophilus, alongside with spores of Aspergillus niger, were exposed to an experimental chamber simulating Martian environmental conditions (constant temperatures of about - 11 °C, low pressure of approximately 6 mbar, a CO 2 atmosphere, and 2 h of daily UV irradiation). We evaluated colony-forming units (CFU) and water content at three different regolith depths before and after exposure periods of 3 and 7 days, respectively. Each organism was tested under three conditions: one without the addition of salts to the regolith, one containing sodium chlorate, and one with sodium perchlorate. Our results reveal that the residual water content after the exposure experiments increased with regolith depth, along with the organism survival rates in chlorate-containing and salt-free samples. The survival rates of the three organisms in perchlorate-containing regolith were consistently lower for all organisms and depths compared to chlorate, with the most significant difference being observed at a depth of 10-12 cm, which corresponds to the depth with the highest residual water content. The postulated reason for this is an increase in the salt concentration at this depth due to the freezing of water, showing that for these organisms, perchlorate brines are more toxic than chlorate brines under the experimental conditions. This underscores the significance of chlorate salts when considering the habitability of Martian environments., (© 2024. The Author(s).)

Mars is a particularly attractive candidate among known astronomical objects to potentially host life. Results from space exploration missions have provided insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to its toxicity. However, it can also provide potential benefits, such as producing brines by deliquescence, like those thought to exist on present-day Mars. Here we show perchlorate brines support folding and catalysis of functional RNAs, while inactivating representative protein enzymes. Additionally, we show perchlorate and other oxychlorine species enable ribozyme functions, including homeostasis-like regulatory behavior and ribozyme-catalyzed chlorination of organic molecules. We suggest nucleic acids are uniquely well-suited to hypersaline Martian environments. Furthermore, Martian near- or subsurface oxychlorine brines, and brines found in potential lifeforms, could provide a unique niche for biomolecular evolution., (© 2024. The Author(s).)

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., (© 2024. The Author(s), under exclusive licence to Springer Nature Japan KK.)

The conventional perchlorate (ClO 4 - ) reduction typically necessitates anaerobic conditions. However, in this study, we observed efficient ClO 4 - reduction using CH 4 as the electron donor in a microaerobic environment. The maximum ClO 4 - removal flux of 2.18 g/m 2 ·d was achieved in CH 4 -based biofilm. The kinetics of ClO 4 - reduction showed significant differences, with trace oxygen increasing the reduction rate of ClO 4 - , whereas oxygen levels exceeding 2 mg/L decelerated the ClO 4 - reduction. In the absence of exogenous oxygen, anaerobic methanotrophic (ANME) archaea contribute more than 80% electrons through the reverse methanogenesis pathway for ClO 4 - reduction. Simultaneously, microorganisms activate CH 4 by utilizing oxygen generated from chlorite (ClO 2 - ) disproportionation. In the presence of exogenous oxygen, methane oxidizers predominantly consume oxygen to drive the aerobic oxidation of methane. It is indicated that methane oxidizers and perchlorate reducing bacteria can form aggregates to resist external oxygen shocks and achieve efficient ClO 4 - reduction under microaerobic condition. These findings provide new insights into biological CH 4 mitigation and ClO 4 - removal in hypoxic environment., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The environmental contaminant perchlorate impairs the synthesis of thyroid hormones by reducing iodine uptake into the thyroid gland. Despite this known action, moderate doses of perchlorate do not significantly alter serum thyroid hormone in rat pups born to exposed dams. We examined perchlorate dosimetry and responsivity of the thyroid gland and brain in offspring following maternal exposure to perchlorate. Pregnant rat dams were delivered perchlorate in drinking water (0, 30, 100, 300, 1000 ppm) from gestational day 6 to postnatal day (PN) 21. Perchlorate was present in the placenta, milk, and serum, the latter declining in pups over the course of lactation. Serum and brain thyroid hormone were reduced in pups at birth but recovered to control levels by PN2. Dramatic upregulation of Nis was observed in the thyroid gland of the exposed pup. Despite the return of serum thyroid hormone to control levels by PN2, expression of several TH-responsive genes was altered in the PN14 pup brain. Contextual fear learning was unimpaired in the adults, supporting previous reports. Declining levels of serum perchlorate and a profound upregulation of Nis gene expression in the thyroid gland are consistent with the rapid return to the euthyroid state in the neonate. However, despite this recovery, thyroid hormone insufficiencies in serum and brain beginning in utero and present at birth appear sufficient to alter TH action in the fetus and subsequent trajectory of brain development. Biomarkers of that altered trajectory remain in the brain of the neonate, demonstrating that perchlorate is not devoid of effects on the developing brain., (Published by Oxford University Press on behalf of the Society of Toxicology 2023.)

The mechanism of perchlorate resistance of the desert cyanobacterium Chroococcidiopsis sp. CCMEE 029 was investigated by assessing whether the pathways associated with its desiccation tolerance might play a role against the destabilizing effects of this chaotropic agent. During 3 weeks of growth in the presence of 2.4 mM perchlorate, an upregulation of trehalose and sucrose biosynthetic pathways was detected. This suggested that in response to the water stress triggered by perchlorate salts, these two compatible solutes play a role in the stabilization of macromolecules and membranes as they do in response to dehydration. During the perchlorate exposure, the production of oxidizing species was observed by using an oxidant-sensing fluorochrome and determining the expression of the antioxidant defense genes, namely superoxide dismutases and catalases, while the presence of oxidative DNA damage was highlighted by the over-expression of genes of the base excision repair. The involvement of desiccation-tolerance mechanisms in the perchlorate resistance of this desert cyanobacterium is interesting since, so far, chaotropic-tolerant bacteria have been identified among halophiles. Hence, it is anticipated that desert microorganisms might possess an unrevealed capability of adapting to perchlorate concentrations exceeding those naturally occurring in dry environments. Furthermore, in the endeavor of supporting future human outposts on Mars, the identified mechanisms might contribute to enhance the perchlorate resistance of microorganisms relevant for biologically driven utilization of the perchlorate-rich soil of the red planet., (© 2023 Phycological Society of America.)

Perchlorate, a widespread environmental contaminant originating from various industrial applications, agricultural practices, and natural sources, poses potential risks to ecosystems and human health. While previous studies have highlighted its influence on the thyroid endocrine system and its impact on gonadal maturation, reproduction, and sex hormone synthesis, the specific interplay between thyroid and steroid hormones, in this context, remains largely unexplored. Therefore, this study was undertaken to investigate the adverse effects and underlying mechanisms triggered by exposure to sodium perchlorate (SP) on reproductive endocrine activity in zebrafish. For 21 d, the fish were exposed to test SP concentrations (0, 3, 30, 300 mg/L), which were determined based on the exposure concentrations that induced various toxic effects in the fish, considering naturally occurring concentrations. Exposure to SP, except at 3 mg/L in males, significantly decreased the production of thyroid hormone (TH) in both female and male zebrafish. Moreover, gonadal steroid levels were markedly reduced in both sexes. The expression of hepatic vitellogenin (VTG) mRNA in female zebrafish was significantly decreased, whereas aromatase activity in male zebrafish was significantly elevated in the SP exposure groups. The reduced levels of THs and gonadal steroid hormones were strongly correlated. Abnormal responses to SP exposure led to reduced reproductive success in the 300 mg/L SP exposure group. These findings indicate that prolonged and continuous exposure to a specific concentration of SP may lead to long-term reproductive problems in zebrafish, primarily through hormonal imbalances and suppression of hepatic VTG mRNA expression., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Perchlorate (ClO 4 - ) is a type of novel, widely distributed, and persistent inorganic pollutant. However, the impacts of perchlorate on freshwater algae remain unclear. In this study, the response and defense mechanisms of microalgae (Chlamydomonas reinhardtii) under perchlorate stress were investigated by integrating physiological and biochemical monitoring, transcriptomics, and metabolomics. Weighted gene co-expression network analysis (WGCNA) of transcriptome data was used to analyze the relationship between genes and phenotype and screen the key pathways. C. reinhardtii exhibited aggregate behavior when exposed to 100- and 200-mM perchlorate but was restored to its unicellular lifestyle when transferred to fresh medium. WGCNA results found that the "carbohydrate metabolism" and "lipid metabolism" pathways were closely related to cell aggregation phenotype. The differential expression genes (DEGs) and differentially accumulated metabolites (DAMs) of these pathways were upregulated, indicating that the lipid and carbohydrate metabolisms were enhanced in aggregated cells. Additionally, most genes and metabolites related to phytohormone abscisic acid (ABA) biosynthesis and the mitogen-activated protein kinase (MAPK) signaling pathway were significantly upregulated, indicating their crucial roles in the signal transmission of aggregated cells. Meanwhile, in aggregated cells, extracellular polymeric substances (EPS) and lipid contents increased, photosynthesis activity decreased, and the antioxidant system was activated. These characteristics contributed to C. reinhardtii's improved resistance to perchlorate stress. Above results demonstrated that cell aggregation behavior was the principal defense strategy of C. reinhardtii against perchlorate. Overall, this study sheds new light on the impact mechanisms of perchlorate to aquatic microalgae and provides multi-omics insights into the research of multicellular-like aggregation as an adaptation strategy to abiotic stress. These results are beneficial for assessing the risk of perchlorate in aquatic environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

This research investigates the biodegradation of perchlorate in the presence of the co-contaminants nitrate and chlorate using soluble and slow-release carbon sources. In addition, the impact of bio-augmentation and dilution, which results in lower total dissolved salts (TDS) and contaminant levels, is examined. Laboratory microcosms were conducted using actual groundwater and soils from a contaminated aquifer. The results revealed that both soluble and slow-release carbon sources support biodegradation of contaminants in the sequence nitrate > chlorate > perchlorate. Degradation rates, including and excluding lag times, revealed that the overall impact of the presence of co-contaminants depends on degradation kinetics and the relative concentrations of the contaminants. When the lag time caused by the presence of the co-contaminants is considered, the degradation rates for chlorate and perchlorate were two to three times slower. The results also show that dilution causes lower initial contaminant concentrations, and consequently, slower degradation rates, which is not desirable. On the other hand, the dilution resulting from the injection of amendments to support remediation promotes desirably lower salinity levels. However, the salinity associated with the presence of sulfate does not inhibit biodegradation. The naturally occurring bacteria were able to support the degradation of all contaminants. Bio-augmentation was effective only in diluted microcosms. Proteobacteria and Firmicutes were the dominant phyla identified in the microcosms., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Microbial reduction has been considered an effective way to remove perchlorate (ClO 4 - ), during which, additional electron donors and carbon sources are required. This work aims to study the potential of fermentation broth of food waste (FBFW) serving as an electron donor for ClO 4 - biodegradation, and further investigates the variance of the microbial community. The results showed that FBFW without anaerobic inoculum at 96 h (F-96) exhibited the highest ClO 4 - removal rate of 127.09 mg/L/d, attributed to higher acetate and lower ammonium contents in the F-96 system. In a 5 L continuous stirred-tank reactor (CSTR), with a 217.39 g/m 3 ·d ClO 4 - loading rate, 100% removal efficiency of ClO 4 - was achieved, indicating that the application of FBFW in the CSTR showed satisfactory performance for ClO 4 - degradation. Moreover, the microbial community analysis revealed that Proteobacteria and Dechloromonas contributed positively to ClO 4 - degradation. Therefore, this study provided a novel approach for the recovery and utilization of food waste, by employing it as a cost-effective electron donor for ClO 4 - biodegradation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Ammunition wastewater contains toxic nitrated explosives like RDX and oxyanions like nitrate and perchlorate. Its treatment is challenged by low efficiency due to contaminant recalcitrance and high cost due to multiple processes needed for separately removing different contaminant types. This paper reports a H 2 -based low-energy strategy featuring the treatment of explosives via catalytic denitration followed by microbial mineralization coupled with oxyanion reduction. After a nitrate- and perchlorate-reducing biofilm incapable of RDX biodegradation was coated with palladium nanoparticles (Pd 0 NPs), RDX was rapidly denitrated with a specific catalytic activity of 8.7 g cat -1 min -1 , while biological reductions of nitrate and perchlorate remained efficient. In the subsequent 30-day continuous test, >99% of RDX, nitrate, and perchlorate were coremoved, and their effluent concentrations were below their respective regulation levels. Detected intermediates and shallow metagenome analysis suggest that the intermediates after Pd-catalytic denitration of RDX ultimately were enzymatically utilized by the nitrate- and perchlorate-reducing bacteria as additional electron donor sources.

If life exists on Mars, it would face several challenges including the presence of perchlorates, which destabilize biomacromolecules by inducing chaotropic stress. However, little is known about perchlorate toxicity for microorganisms on the cellular level. Here, we present the first proteomic investigation on the perchlorate-specific stress responses of the halotolerant yeast Debaryomyces hansenii and compare these to generally known salt stress adaptations. We found that the responses to NaCl and NaClO 4 -induced stresses share many common metabolic features, for example, signalling pathways, elevated energy metabolism, or osmolyte biosynthesis. Nevertheless, several new perchlorate-specific stress responses could be identified, such as protein glycosylation and cell wall remodulations, presumably in order to stabilize protein structures and the cell envelope. These stress responses would also be relevant for putative life on Mars, which-given the environmental conditions-likely developed chaotropic defence strategies such as stabilized confirmations of biomacromolecules or the formation of cell clusters., (© 2022 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.)

Thyroid disruptors are found in food, atmosphere, soil, and water. These contaminants interfere with the thyroid function through the impairment of thyroid hormone synthesis, plasma transport, peripheral metabolism, transport into the target cells, and thyroid hormone action. It is well known that iodide uptake mediated by the sodium-iodide symporter (NIS) is the first limiting step involved in thyroid hormones production. Therefore, it has been described that several thyroid disruptors interfere with the thyroid function through the regulation of NIS expression and/or activity. Perchlorate, nitrate, and thiocyanate competitively inhibit the NIS-mediated iodide uptake. These contaminants are mainly found in food, water and in the smoke of cigarettes. Although the impact of the human exposure to these anions is highly controversial, some studies indicated their deleterious effects in the thyroid function, especially in individuals living in iodine deficient areas. Considering the critical role of thyroid function and the production of thyroid hormones for growth, metabolism, and development, this review summarizes the impact of the exposure to these NIS-inhibitors on thyroid function and their consequences for human health., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Serrano-Nascimento and Nunes.)

Perchlorate and chlorate are both strong oxidants and thyroid toxicants that are widely distributed in soil, water and human foods. The red swamp crayfish (Procambarus clarkii) is a common aquatic organism that is popular in Chinese culinary dishes. Dietary intake is the main route of human exposure to perchlorate and chlorate, though the health risks of crayfish consumption are unknown. Thus, this study investigated the quantities of perchlorate and chlorate in red swap crayfish from sampling sites in five provinces located near the Yangtze River in China, along with the associated health risks of consuming this species. Perchlorate was detected in 55.6-100 % of crayfish samples in each sampling location, and chlorate was found in 100 % of samples cross all sites. Concentrations of perchlorate in crayfish from upstream provinces (Hubei, Hunan and Jiangxi) were higher than those from downstream provinces (Anhui and Jiangsu). Perchlorate and chlorate concentrations were positively correlated in crayfish, suggesting that chlorate may be a degradation byproduct of perchlorate. The quantities of both pollutants in hepatopancreas tissue were higher than in muscle tissues (p < 0.05), such that we do not recommend ingesting crayfish hepatopancreas. Hazard quotient (HQ) values for chlorate in crayfish were <1 across all provinces, suggesting no potential health risk of chlorate exposure through crayfish consumption. However, perchlorate concentrations in crayfish from the Jiangxi province had an associated HQ value >1, suggesting potential risks for human health. These results will be useful in informing mitigation measures aimed at reducing perchlorate exposure associated with crayfish consumption., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

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., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

Thiocyanate (SCN - ) alters the potency of certain agonists for the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, and dysfunctions in AMPA receptor signaling are considered to underlie a number of neurological diseases. While humans may be exposed to SCN - from the environment, including food sources, a carrier-mediated system transports SCN - from the brain into the blood and is an important regulator of SCN - distribution in the central nervous system. The assessment of this SCN - efflux system in the brain would thus be useful for understanding the mechanisms underlying the neurotoxicity of SCN - and for elucidating the relationship between the efflux system and brain diseases. However, the currently available technique for studying SCN - efflux is severely limited by its invasiveness. Here, we describe the development of a SCN - protracer, 9-pentyl-6-[ 11 C]thiocyanatopurine ([ 11 C] 1 ), to overcome this limitation. [ 11 C] 1 was synthesized by the reaction of the iodo-precursor and [ 11 C]SCN - or the reaction of the disulfide precursor with [ 11 C]NH 4 CN. The protracer [ 11 C] 1 entered the brain after intravenous injection into mice and was rapidly metabolized to [ 11 C]SCN - , which was then eliminated from the brain. The efflux of [ 11 C]SCN - was dose-dependently inhibited by perchlorate, a monovalent anion, and the highest dose caused an 82% reduction in the efflux rate. Our findings demonstrate that [ 11 C] 1 can be used for the noninvasive and quantitative assessment of the SCN - efflux system in the brain.

The biological reduction of slow degradation contaminants such as perchlorate (ClO 4 - ) 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, K s = 37.619 mg/L and q max = 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.

Iodine is essential for the production of thyroid hormones. Perchlorate is an environmental contaminant that interferes with iodine uptake into the thyroid gland to reduce thyroid hormone synthesis. As thyroid hormones are critical for brain development, exposure to perchlorate during pregnancy is of concern for the developing fetal brain. In this study, we (1) define profiles of thyroid hormone in the maternal and fetal compartments of pregnant rats in response to inhibition of the sodium-iodide symporter (NIS) by perchlorate and (2) expand inquiry previously limited to serum to include fetal thyroid gland and brain. Perchlorate was added to the drinking water (0, 1, 30, 300, and 1000 ppm) of pregnant rat dams from gestational days (GD) 6-20. On GD20, blood, thyroid gland, and brain were collected from the fetus and dam for thyroid hormone and molecular analyses. Thyroid gland and serum thyroid hormones were dose-dependently reduced, with steeper declines evident in the fetus than in the dam. The thyroid gland revealed perturbations of thyroid hormone-action with greater sensitivity in the fetus than the dam. Thyroid hormones and thyroid hormone-responsive gene expression were reduced in the fetal cortex portending effects on brain development. These findings are the first quantitative assessments of perchlorate-induced deficits in the fetal thyroid gland and fetal brain. We provide a conceptual framework to develop a quantitative NIS adverse outcome pathway for serum thyroid hormone deficits and the potential to impact the fetal brain. Such a framework may also serve to facilitate the translation of in vitro bioactivity to the downstream in vivo consequences of NIS inhibition in the developing fetus., (Published by Oxford University Press on behalf of the Society of Toxicology 2022.)

Perchlorate, a persistent pollutant, interferes with iodine uptake by the thyroid. Perchlorate exposure mainly occurs through ingested food; understanding the bioaccessibility and bioavailability of perchlorate in foods facilitate more accurate human health risk assessments. An in vitro digestion/Caco-2 cell model was used for this research. The bioaccessibility of perchlorate in the control group, lettuce, rice and formula was 93.45%, 70.14%, 70.25%, and 63.68%, respectively. The bioavailability of perchlorate was as follows: control group, 43.45%; rice, 37.17%; lettuce, 35.13%; and formula, 30.72%. The absorptive apparent permeability coefficient (Papp) of the control, lettuce, rice, and formula was 30-101 nm/s, 32-65 nm/s, 54-161 nm/s, and 41-88 nm/s, respectively. The results suggested that the risk from perchlorate was overestimated only when considering the content of perchlorate in foods and that the presence of food matrices reduced perchlorate bioavailability by differing degrees., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The dimethylsulfoxide (DMSO) reductase family of enzymes has many subfamilies catalysing unique biogeochemical reactions. It also has many uncharacterized subfamilies. Comparative genomics predicted one such subfamily to participate in a key step of the chlorine cycle because of a conserved genetic association with chlorite dismutase, implying they produce chlorite through chlorate or perchlorate reduction. We determined the activity of the uncharacterized enzyme by comparing strains in the phototrophic genus Rhodoplanes that encode either a typical perchlorate reductase or the uncharacterized enzyme. Rpl. piscinae and Rpl. elegans, which encode perchlorate reductase, grew by using perchlorate as an electron acceptor. In contrast, Rpl. roseus, which encodes the uncharacterized enzyme, grew by chlorate reduction but not by perchlorate reduction. This is the first report of perchlorate and chlorate being used as respiratory electron acceptors by phototrophs. When both chlorate and perchlorate were present, Rpl. roseus consumed only chlorate. Highly concentrated Rpl. roseus cells showed some perchlorate consumption, but chlorate consumption occurred at a 10-fold higher rate. Together, these genomic and physiological data define a new group of chlorate reductases. Some organisms encode both this chlorate reductase and a perchlorate reductase, raising new questions about the physiology and evolution of chlorine oxyanion respiration., (© 2020 Society for Applied Microbiology and John Wiley & Sons Ltd.)

We present the hypothesis that microorganisms can change the freezing/melting curve of cold salty solutions by protein expression, as it is known that proteins can affect the liquid-to-ice transition, an ability that could be of ecological advantage for organisms on Earth and on Mars. We tested our hypothesis by identifying a suitable candidate, the well-known psycrophile and halotolerant bacteria Rhodococcus sp. JG3, and analyzing its response in culture conditions that included specific hygroscopic salts relevant to Mars-that is, highly concentrated magnesium perchlorate solutions of 20 wt % and 50 wt % Mg(ClO 4 ) 2 at both end members of the eutectic concentration (44 wt %)-and subfreezing temperatures (263 K and 253 K). Using a combination of techniques of molecular microbiology and aqueous geochemistry, we evaluated the potential roles of proteins over- or underexpressed as important players in different mechanisms for the adaptability of life to cold environments. We recorded the changes observed by micro-differential scanning calorimetry. Unfortunately, Rhodococcus sp. JG3 did not show our hypothesized effect on the melting characteristics of cold Mg-perchlorate solutions. However, the question remains as to whether our novel hypothesis that halophilic/psychrophilic bacteria or archaea can alter the freezing/melting curve of salt solutions could be validated. The null result obtained after analyzing just one case lays the foundation to continue the search for proteins produced by microorganisms that thrive in very cold, high-saline solutions, which would involve testing different microorganisms with different salt components. The immediate implications for the habitability of Mars are discussed.

Regulation of the expression of the gene for chlorite dismutase (cld), located on the chlorate reduction composite transposon of the chlorate reducer Ideonella dechloratans, was studied. A 200 bp upstream sequence of the cld gene, and mutated and truncated versions thereof, was used in a reporter system in Escherichia coli. It was found that a sequence within this upstream region, which is nearly identical to the canonical FNR-binding sequence of E. coli, is necessary for anaerobic induction of the reporter gene. Anaerobic induction was regained in an FNR-deficient strain of E. coli when supplemented either with the fnr gene from E. coli or with a candidate fnr gene cloned from I. dechloratans. In vivo transcription of the suggested fnr gene of I. dechloratans was demonstrated by qRT-PCR. Based on these results, the cld promoter of I. dechloratans is suggested to be a class II-activated promoter regulated by an FNR-type protein of I. dechloratans. No fnr-type genes have been found on the chlorate reduction composite transposon of I. dechloratans, making anaerobic upregulation of the cld gene after a gene transfer event dependent on the presence of an fnr-type gene in the recipient., (© 2020 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)

The Na + /I - symporter (NIS), the plasma membrane protein that actively transports I - (stoichiometry 2Na + :1I - ) in thyroid physiology and radioiodide-based thyroid cancer treatment, also transports the environmental pollutant perchlorate (stoichiometry 1Na + :1ClO 4 - ), which competes with I - for transport. Until now, the mechanism by which NIS transports different anion substrates with different stoichiometries has remained unelucidated. We carried out transport measurements and analyzed these using a statistical thermodynamics-based equation and electrophysiological experiments to show that the different stoichiometry of ClO 4 - transport is due to ClO 4 - binding to a high-affinity non-transport allosteric site that prevents Na + from binding to one of its two sites. Furthermore, low concentrations of ClO 4 - inhibit I - transport not only by competition but also, critically, by changing the stoichiometry of I - transport to 1:1, which greatly reduces the driving force. The data reveal that ClO 4 - pollution in drinking water is more dangerous than previously thought.

Biofilm reactors retain microbial cells in the form of biofilm which is attached to free moving or fixed carrying materials, thus providing a high active biomass concentration and automatic liquid and solid separation. Nowadays, microbial biofilm reactors have been widely used in high-strength wastewater treatment where very high pollutant removal efficiency is required, which usually requires excessive space and aeration energy for conventional activated sludge-based treatment. This paper provides an overview of microbial biofilm reactors developed over the last half-century, including moving bed biofilm reactor (MBBR), trickling filter (TF) reactor, rotating biological contactor (RBC), membrane biofilm reactor (MBfR), passive aeration simultaneous nitrification and denitrification (PASND) biofilm reactor, for their applications in high-strength wastewater treatment of not only removing carbon, nitrogen, sulphur but also a variety of oxidized contaminants including perchlorate and bromate. Despite the advance of biofilm reactor that exhibits high resistance to excessive pollutants loading, its drawbacks both from engineering and microbiological point of view are reviewed. The future prospects of biofilm reactor are also discussed in this review paper.

A novel, ex-situ remediation process for perchlorate contaminated soil is reported in this study. This approach comprises washing the contaminated soil with water, followed by treatment of the wash water in a bioreactor. The treated water reused for the next batch of soil, and the cycle continued. The pilot-scale treatment unit comprising of a soil washing unit (0.75 m3) and a fixed-film bioreactor (140 L), both connected in series for continuous operation for a period of three months. The bioreactor was inoculated with a novel perchlorate reducing microbial consortium comprising Serratia marcescens (Gen bank no. HM751096), Bacillus pumilus (Gen bank no. JQ820452) and Micrococcus sp. (Gen bank no. KJ410671). The microbial activity was supported by glucose (glucose/perchlorate ratio = 5), and trace mineral solution. In a typical washing cycle, 2.5 g perchlorate (KClO4) spiked in 670 kg soil was completely removed in three washing cycles, that completed in 6.3 h consuming ∼360 L water. The pooled wash water containing perchlorate at 8.5 mg/L was treated completely in the bioreactor operated at 4.5 h HRT and -200 mV ORP. Compared with both in-situ and ex-situ remediation methods reported, the present approach has many advantages for treating perchlorate contaminated soil., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

No instrument capable of direct life detection has been included on a mission payload to Mars since NASA's Viking missions in the 1970s. This prevents us from discovering whether life is or ever was present on Mars. DNA is an ideal target biosignature since it is unambiguous, nonspecific, and readily detectable with nanopore sequencing. Here, we present a proof-of-concept utilization of the Oxford Nanopore Technologies (ONT) MinION sequencer for direct life detection and show how it can complement results from established space mission instruments. We used nanopore sequencing data from the MinION to detect and characterize the microbial life in a set of paleochannels near Hanksville, UT, with supporting data from X-ray diffraction, reflectance spectroscopy, Raman spectroscopy, and Life Detector Chip (LDChip) microarray immunoassay analyses. These paleochannels are analogs to martian sinuous ridges. The MinION-generated metagenomes reveal a rich microbial community dominated by bacteria and containing radioresistant, psychrophilic, and halophilic taxa. With spectral data and LDChip immunoassays, these metagenomes were linked to the surrounding Mars analog environment and potential metabolisms ( e.g. , methane production and perchlorate reduction). This shows a high degree of synergy between these techniques for detecting and characterizing biosignatures. We also resolved a prospective lower limit of ∼0.001 ng of DNA required for successful sequencing. This work represents the first determination of the MinION's DNA detection limits beyond ONT recommendations and the first whole metagenome analysis of a sinuous ridge analog.

The sodium iodide symporter (NIS) transports iodide, which is necessary for thyroid hormone production. NIS also transports other monovalent anions such as tetrafluoroborate (BF4-), pertechnetate (TcO4-), and thiocyanate (SCN-), and is competitively inhibited by perchlorate (ClO4-). However, the mechanisms of substrate selectivity and inhibitor sensitivity are poorly understood. Here, a comparative approach was taken to determine whether naturally evolved NIS proteins exhibit variability in their substrate transport properties. The NIS proteins of thirteen animal species were initially assessed, and three species from environments with differing iodide availability, freshwater species Danio rerio (zebrafish), saltwater species Balaenoptera acutorostrata scammoni (minke whale), and non-aquatic mammalian species Homo sapiens (human) were studied in detail. NIS genes from each of these species were lentivirally transduced into HeLa cells, which were then characterized using radioisotope uptake assays, 125I- competitive substrate uptake assays, and kinetic assays. Homology models of human, minke whale and zebrafish NIS were used to evaluate sequence-dependent impact on the organization of Na+ and I- binding pockets. Whereas each of the three proteins that were analyzed in detail concentrated iodide to a similar degree, their sensitivity to perchlorate inhibition varied significantly: minke whale NIS was the least impacted by perchlorate inhibition (IC50 = 4.599 μM), zebrafish NIS was highly sensitive (IC50 = 0.081 μM), and human NIS showed intermediate sensitivity (IC50 = 1.566 μM). Further studies with fifteen additional substrates and inhibitors revealed similar patterns of iodide uptake inhibition, though the degree of 125I- uptake inhibition varied with each compound. Kinetic analysis revealed whale NIS had the lowest Km-I and the highest Vmax-I. Conversely, zebrafish NIS had the highest Km and lowest Vmax. Again, human NIS was intermediate. Molecular modeling revealed a high degree of conservation in the putative ion binding pockets of NIS proteins from different species, which suggests the residues responsible for the observed differences in substrate selectivity lie elsewhere in the protein. Ongoing studies are focusing on residues in the extracellular loops of NIS as determinants of anion specificity. These data demonstrate significant transport differences between the NIS proteins of different species, which may be influenced by the unique physiological needs of each organism. Our results also identify naturally-existing NIS proteins with significant variability in substrate transport kinetics and inhibitor sensitivity, which suggest that the affinity and selectivity of NIS for certain substrates can be altered for biotechnological and clinical applications. Further examination of interspecies differences may improve understanding of the substrate transport mechanism., Competing Interests: I have read the journal's policy and the authors of this manuscript have the following competing interests: S.J.R. is a cofounder and holds equity in Imanis Life Sciences, LLC. S.C.C., H.R.Z., and S.Y.N. declare no competing interests. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Inhibitors can be used to control the functionality of microbial communities by targeting specific metabolisms. The targeted inhibition of dissimilatory sulfate reduction limits the generation of toxic and corrosive hydrogen sulfide across several industrial systems. Sulfate-reducing microorganisms (SRM) are specifically inhibited by sulfate analogs, such as perchlorate. Previously, we showed pure culture SRM adaptation to perchlorate stress through mutation of the sulfate adenylyltransferase, a central enzyme in the sulfate reduction pathway. Here, we explored adaptation to perchlorate across unconstrained SRM on a community scale. We followed natural and bio-augmented sulfidogenic communities through serial transfers in increasing concentrations of perchlorate. Our results demonstrated that perchlorate stress altered community structure by initially selecting for innately more resistant strains. Isolation, whole-genome sequencing, and molecular biology techniques allowed us to define subsequent genetic mechanisms of adaptation that arose across the dominant adapting SRM. Changes in the regulation of divalent anion:sodium symporter family transporters led to increased intracellular sulfate to perchlorate ratios, allowing SRM to escape the effects of competitive inhibition. Thus, in contrast to pure-culture results, SRM in communities cope with perchlorate stress via changes in anion transport and its regulation. This highlights the value of probing evolutionary questions in an ecological framework, bridging the gap between ecology, evolution, genomics, and physiology.

The H 2 /CO 2 -based membrane biofilm reactor (H 2 /CO 2 -MBfR) that effectively combines microporous diffusions of H 2 and CO 2 is efficient in removing perchlorate (ClO 4 - ). Nitrate (NO 3 - ) is a common oxidized contaminant frequently coexists with ClO 4 - in water, with the NO 3 - concentration in most ClO 4 - -contaminated waters being several orders of magnitude higher than ClO 4 - . Determining the effect of NO 3 - on ClO 4 - reduction is a critical issue in practice. The ClO 4 - reduction performance, biofilm microbial community and influencing mechanism were investigated under a series of feed NO 3 - loadings in this work. ClO 4 - reduction was slightly promoted when NO 3 - -N levels were <10 mg/L and inhibited at higher NO 3 - -N levels. Denitrification competed more strongly for H 2 than ClO 4 - reduction, regardless of H 2 availability. A higher NO 3 - -N loading was a strong driving force to change the biofilm microbial community. Betaproteobacteria were the dominant bacteria at all stages, and the biofilm reactor was enriched in Methyloversatilis and Zoogloea (31.9-56.5% and 10.6-25.8%, respectively). Changes in the relative amounts of Methyloversatilis and Zoogloea coincided with changes in the ClO 4 - fluxes and removal efficiencies and the relative abundances of nitrogen cycle functional genes. These results suggest that Methyloversatilis and Zoogloea likely follow independent reduction mechanisms for ClO 4 - removal., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A specially designed CH 4 -based membrane biofilm batch reactor (MBBR) was applied to investigate anaerobic methane oxidation coupled to perchlorate reduction (AnMO-PR). The 0.21 mM ClO 4 - added in the first stage of operation was completely reduced in 28 days, 0.40 mM ClO 4 - was reduced within 23 days in stage 2, and 0.56 mM of ClO 4 - was reduced within 30 days in stage 3. Although some chlorate (ClO 3 - ) accumulated, the recovery of Cl - was over 92%. Illumina sequencing of the 16S rRNA gene documented that the bacterial community was mainly composed by perchlorate-reducing bacteria (PRB), methanotrophic bacteria, and archaea. Real-time quantitative PCR showed the archaeal 16S rRNA and mcrA genes increased as more ClO 4 - was reduced, and the predominant archaea belonged to Methanosarcina mazei, which is related to ANME-3, an archaeon able to perform reverse methanogenesis. Several pieces of evidence support that ClO 4 - reduction by the MBBR biofilm occurred via a synergism between Methanosarcina and PRB: Methanosarcina oxidized methane through reverse methanogesis and provided electron donor for PRB to reduce ClO 4 - . Because methanotrophs were present, we cannot rule out that they also were involved in AnMO-PR if they received O 2 generated by disproportionation of ClO 2 - from the PRB., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Biological reduction is an effective method for removal of perchlorate (ClO 4 - ), where perchlorate is transformed into chloride by perchlorate-reducing bacteria (PRB). An external electron donor is required for autotrophic and heterotrophic reduction of perchlorate. Therefore, plenty of suitable electron donors including organic (e.g., acetate, ethanol, carbohydrate, glycerol, methane) and inorganic (e.g., hydrogen, zero-valent iron, element sulfur, anthrahydroquinone) as well as the cathode have been used in biological reduction of perchlorate. This paper reviews the application of various electron donors in biological perchlorate reduction and their influences on treatment efficiency of perchlorate and biological activity of PRB. We discussed the criteria for selection of appropriate electron donor to provide a flexible strategy of electron donor choice for the bioremediation of perchlorate-contaminated water.

The combined anaerobic baffled reactors (ABRs) of heterotrophic and sulfur-based autotrophic processes were first investigated for the removal of high perchlorate concentration under different feeding strategies. The removal efficiency of the step-feeding ABR (SF-ABR) reached 97.56% at 800 mg/L perchlorate, which was significantly superior to the normal-feeding ABR (NF-ABR). In three components of the extracellular polymeric substances (EPS), the fluorescence intensity of the tryptophan-like component were identified by fluorescence excitation-emission matrix (EEM) spectra with parallel factor (PARAFAC) analysis, and exhibited a positive relationship with the perchlorate removal rate in the heterotrophic perchlorate reduction unit (HPR unit) of the SF-ABR (R 2  = 0.9791) and NF-ABR (R 2  = 0.9860). Bacterial community analysis suggested the dominating perchlorate reducing bacteria and the diversity in two ABRs. Principal component analysis indicated that the electron donor affected the microbial community structures. The study confirms that the SF-ABR is a powerful bioreactor for the combined heterotrophic and sulfur-based autotrophic process., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The presence of perchlorate on Mars suggests a possible energy source for sustaining microbial life. Perchlorate-reducing microbes have been isolated from perchlorate-contaminated soils and sediments on the Earth, but to date, never from an environment that is naturally enriched in perchlorate. The arid Pilot Valley paleolake basin in Utah is a Mars analog environment whose sediments are naturally enriched with up to ∼6.5 μg kg -1 perchlorate oxyanions. Here, we present results of field and laboratory studies indicating that perchlorate-reducing microorganisms co-occur with this potential electron acceptor. Biogeochemical data suggest ongoing perchlorate reduction; phylogenetic data indicate the presence of diverse microbial communities; and laboratory enrichments using Pilot Valley sediments show that resident microbes can reduce perchlorate. This is the first article of the co-existence of perchlorate-reducing microbes in an environment where perchlorate occurs naturally, arguing for Pilot Valley's utility as an analog for studying biogeochemical processes that may have occurred, and may yet still be occurring, in ancient martian lacustrine sediments.

To remove high-strength perchlorate, dissimilatory perchlorate reducing granular sludge (DPR-GS) was first cultivated. Three identical UASB reactors were set up under different seed sludge and up-flow velocities (R AS : active sludge (AS) and constant up-flow velocities; R DGS : denitrifying granular sludge (DGS) and constant up-flow velocities; R DGS-f : DGS and fluctuating up-flow velocities). The AS in the R AS was completely granulated by day 117, while the DGS in the R DGS and R DGS-f were both shortened the granulation time to 99 days. In addition, the fluctuating up-flow velocity can better ensure rapid cultivation of DPR-GS. Removal of ClO 4 - loading rate with 7.20 kg/(m 3 ·d) occurred in all three reactors. The results of extracellular polymeric substances (EPS) composition analysis indicated the polysaccharose (PS) promoted the formation of bio-aggregates, while the protein (PN) benefited the granulation of sludge. The analyses of the microbial communities indicated that Sulfurospirillum and Acinetobacter were the dominant dissimilatory perchlorate reducing bacteria., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A perchloric acid-soluble protein (PSP), named here tv-psp1, was identified in Trichomonas vaginalis. It is expressed under normal culture conditions according to expressed sequence tag (EST) analysis. On the other hand, Tv-PSP1 protein was identified by mass spectrometry with a 40% of identity to human PSP (p14.1). Polyclonal antibodies against recombinant Tv-PSP1 (rTv-PSP1) recognized a single band at 13.5 kDa in total protein parasite extract by SDS-PAGE and a high molecular weight band analyzed by native PAGE. Structural analysis of Tv-PSP1, using dynamic light scattering, size exclusion chromatography, and circular dichroism spectroscopy, showed a trimeric structure stable at 7 M urea with 38% α-helix and 14% β-sheet in solution and a molecular weight of 40.5 kD. Tv-PSP1 models were used to perform dynamic simulations over 100 ns suggesting a stable homotrimeric structure. Tv-PSP1 was located in the nucleus, cytoplasm, and hydrogenosomes of T. vaginalis, and the in silico analysis by Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) showed interactions with RNA binding proteins. The preliminary results of RNA degradation analysis with the recombinant Tv-PSP1 showed RNA partial deterioration suggesting a possible putative ribonuclease function.

Perchlorate bioreduction coupled to methane oxidation was successfully achieved without the addition of nitrate or nitrite in a membrane biofilm reactor (MBfR) inoculated with a mixture of freshwater sediments and anaerobic digester sludge as well as return activated sludge. The reactor was operated at different methane pressures (60, 40 and 20 Kpa) and influent perchlorate concentrations (1, 5 and 10 mg/L) to evaluate the biochemical process of perchlorate bioreduction coupled to methane oxidation. Perchlorate was completely reduced with a higher removal flux of 92.75 mg/m 2 ·d using methane as the sole carbon source and electron donor, other than hydrogen or other limiting organics. Quantitative real-time PCR showed that bacteria prevailed over archaea and the abundances of mcrA, pMMO, pcrA, and nirS genes were correlated with the influent perchlorate flux. High-throughput sequencing of 16S rRNA genes demonstrated that the functional community consisted of methanotrophs, methylotrophs, perchlorate-reducing bacteria, as well as various denitrifiers., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Pure bacteria cell (Azospira sp. KJ) and mixed perchlorate reducing bacteria (MPRB) were employed for decomposing the free perchlorate in water as well as the laden perchlorate on surface of quaternary ammonium wheat residuals (QAWR). Results indicated that perchlorate was decomposed by the Azospira sp. KJ prior to nitrate while MPRB was just the reverse. Bio-reduction of laden perchlorate by Azospira sp. KJ was optimal at pH 8.0. In contrast, bio-reduction of laden perchlorate by MPRB was optimal at pH 7.0. Generally, the rate of perchlorate reduction was controlled by the enzyme activity of PRB. In addition, perchlorate recovery (26.0 mg/g) onto bio-regenerated QAWR by MPRB was observed with a small decrease as compared with that (31.1 mg/g) by Azospira sp. KJ at first 48 h. Basically, this study is expected to offer some different ideas on bio-regeneration of perchlorate-saturated adsorbents using biological process, which may provide the economically alternative to conventional methods., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The mechanism for perchlorate reduction was investigated using thiosulfate-driven (T-driven) perchlorate reduction bacteria. The influences of various environmental conditions on perchlorate reduction, including pH, temperature and electron acceptors were examined. The maximum perchlorate removal rate was observed at pH 7.5 and 40 °C. Perchlorate reduction was delayed due to the coexistence of perchlorate-chlorate and perchlorate-nitrate. The mechanism of the T-driven perchlorate reduction electron transport chain (ETC) was also investigated by utilizing different inhibitors. The results were as follows: firstly, the NADH dehydrogenase was not involved in the ETC; secondly, the FAD dehydrogenase and quinone loop participated in the ETC; and thirdly, cytochrome oxidase was the main pathway in the ETC. Meanwhile, microbial consortium structure analysis indicated that Sulfurovum which can oxidize sulfur compounds coupled to the reduction of nitrate or perchlorate was the primary bacterium in the T-driven and sulfur-driven consortium. This study generates a better understanding of the mechanism of T-driven perchlorate reduction., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

A β-class carbonic anhydrase (CA, EC 4.2.1.1) from the pathogenic bacterium Francisella tularensis (FtuβCA) was cloned and purified, and the anion inhibition profile was investigated. Based on the measured kinetic parameters for the enzyme catalyzed CO 2 hydration reaction (k cat of 9.8×10 5 s -1 and a k cat /K M of 8.9×10 7 M -1 s -1 ), FtuβCA is a highly effective enzyme. The activity of FtuβCA was not inhibited by a range of anions that do not typically coordinate Zn(II) effectively, including perchlorate, tetrafluoroborate, and hexafluorophosphate. Surprisingly, some anions which generally complex well with many cations, including Zn(II), also did not effectively inhibit FtuβCA, e.g., fluoride, cyanide, azide, nitrite, bisulphite, sulfate, tellurate, perrhenate, perrhuthenate, and peroxydisulfate. However, the most effective inhibitors were in the range of 90-94µM (sulfamide, sulfamic acid, phenylarsonic and phenylboronic acid). N,N-Diethyldithiocarbamate (K I of 0.31mM) was a moderately potent inhibitor. As Francisella tularensis is the causative agent of tularemia, the discovery of compounds that can interfere with the life cycle of this pathogen may result in novel opportunities to fight antibiotic drug resistance., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Thyroid scintigraphy holds a key place in the etiologic workup of neonatal hypothyroidism. Routine screening for this disorder in maternity hospitals in industrialized countries, for nearly 40 years, has permitted early treatment and thereby helped to prevent its physical and mental complications. Neonatal hypothyroidism affects approximately 1 in 3000 births. The most common causes are abnormal thyroid gland development and defective hormone synthesis by an eutopic thyroid gland. The incidence of the latter has risen in recent years, for reasons that remain unclear. A thorough etiologic workup helps to determine the disease type. Current guidelines recommend thyroid imaging by means of ultrasound and scintigraphy. Ultrasound should be done by a practitioner trained to examine the cervical region of newborns, as the thyroid is very small and must be distinguished from the particular aspect of the "thyroid empty lodge." Ultrasound lacks sensitivity for detecting small ectopic glands but is the gold standard for measuring thyroid dimensions. Scintigraphy provides an etiologic diagnosis in most cases. The two isotopes used in this setting are technetium-99m and iodine-123. The latter isotope gives more contrast and allows the perchlorate discharge test to be performed to detect abnormal iodide organification in the neonate with an eutopic thyroid. If scintigraphy cannot be performed during the neonatal period, a postponed procedure can be achieved after 3 years of age. Close cooperation between the nuclear medicine physician and the pediatric endocrinologist is crucial for timely and optimized scintigraphy., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The genetic and biochemical basis of perchlorate-dependent H 2 S oxidation (PSOX) was investigated in the dissimilatory perchlorate-reducing microorganism (DPRM) Azospira suillum PS (PS). Previously, it was shown that all known DPRMs innately oxidize H 2 S, producing elemental sulfur (S o ). Although the process involving PSOX is thermodynamically favorable ( ΔG °' = -206 kJ ⋅ mol -1 H 2 S), the underlying biochemical and genetic mechanisms are currently unknown. Interestingly, H 2 S is preferentially utilized over physiological electron donors such as lactate or acetate although no growth benefit is obtained from the metabolism. Here, we determined that PSOX is due to a combination of enzymatic and abiotic interactions involving reactive intermediates of perchlorate respiration. Using various approaches, including barcode analysis by sequencing (Bar-seq), transcriptome sequencing (RNA-seq), and proteomics, along with targeted mutagenesis and biochemical characterization, we identified all facets of PSOX in PS. In support of our proposed model, deletion of identified upregulated PS genes traditionally known to be involved in sulfur redox cycling (e.g., Sox, sulfide:quinone reductase [SQR]) showed no defect in PSOX activity. Proteomic analysis revealed differential abundances of a variety of stress response metal efflux pumps and divalent heavy-metal transporter proteins, suggesting a general toxicity response. Furthermore, in vitro biochemical studies demonstrated direct PSOX mediated by purified perchlorate reductase (PcrAB) in the absence of other electron transfer proteins. The results of these studies support a model in which H 2 S oxidation is mediated by electron transport chain short-circuiting in the periplasmic space where the PcrAB directly oxidizes H 2 S to S o The biogenically formed reactive intermediates (ClO 2 - and O 2 ) subsequently react with additional H 2 S, producing polysulfide and S o as end products. IMPORTANCE Inorganic sulfur compounds are widespread in nature, and microorganisms are central to their transformation, thereby playing a key role in the global sulfur cycle. Sulfur oxidation is mediated by a broad phylogenetic diversity of microorganisms, including anoxygenic phototrophs and either aerobic or anaerobic chemotrophs coupled to oxygen or nitrate respiration, respectively. Recently, perchlorate-respiring microorganisms were demonstrated to be innately capable of sulfur oxidation regardless of their phylogenetic affiliation. As recognition of the prevalence of these organisms intensifies, their role in global geochemical cycles is being queried. This is further highlighted by the recently recognized environmental pervasiveness of perchlorate not only across Earth but also throughout our solar system. The inferred importance of this metabolism not only is that it is a novel and previously unrecognized component of the global sulfur redox cycle but also is because of the recently demonstrated applicability of perchlorate respiration in the control of biogenic sulfide production in engineered environments such as oil reservoirs and wastewater treatment facilities, where excess H 2 S represents a significant environmental, process, and health risk, with associated costs approximating $90 billion annually., (Copyright © 2017 Mehta-Kolte et al.)

In this study, we examined the ability of top soil to degrade perchlorate from infiltrating polluted groundwater under unsaturated conditions. Column experiments designed to simulate typical remediation operation of daily wetting and draining cycles of contaminated water amended with an electron donor. Covering the infiltration area with bentonite ensured anaerobic conditions. The soil remained unsaturated, and redox potential dropped to less than -200mV. Perchlorate was reduced continuously from ∼1150mg/L at the inlet to ∼300mg/L at the outlet in daily cycles. Removal efficiency was between 60 and 84%. No signs of bioclogging were observed during three operation months although occasional iron reduction observed due to excess electron donor. Changes in perchlorate reducing bacteria numbers were inferred from an increased in pcrA gene abundances from ∼10 5 to 10 7 copied per gram at the end of the experiment indicating the growth of perchlorate-reducing bacteria. We proposed that the topsoil may serve as a bioreactor to treat high concentrations of perchlorate from the contaminated groundwater. The treated water that infiltrates from the topsoil through the vadose zone could be used to flush perchlorate from the deep vadose zone into the groundwater where it is retrieved again for treatment in the topsoil., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The effects of perchlorate concentration and hydraulic retention time (HRT) on perchlorate reduction characteristics were investigated in a sulfur-based perchlorate reduction reactor.The results showed that the perchlorate was completely removed at HRT of 12 h and the influent perchlorate concentration ranged from 50 mg·L -1 to 194 mg·L -1 ;The perchlorate removal efficiency was 74% at HRT of 4 h and the influent perchlorate concentration was 194 mg·L -1 ;The yield of sulfate was increased by increasing the influent perchlorate concentration and HRT;The influent pH and alkalinity was approximately 8.0 and 500 mg·L -1 CaCO 3 ,and the effluent pH and alkalinity was approximately 6.7 and 100 mg·L -1 CaCO 3 ,respectively;The oxidation reduction potential (ORP) ranged from -380 mV to -330 mV at the bottom of the reactor,however,ORP ranged from -300 mV to -250 mV at the top of the reactor;The molecular biological analysis showed that the microbial consortium structure was different along the flow path in the reactor, Sulfurovum which is known to oxidize sulfur was decreased from 57.78% to 32.19% and Hydrogenophilaceae which is known to oxidize hydrogen sulfide was increased from 4.35% to 22.24%.

A mathematical model for the theoretical evaluation of microbial electrochemical technologies (METs) is presented that incorporates a detailed physico-chemical framework, includes multiple reactions (both at the electrodes and in the bulk phase) and involves a variety of microbial functional groups. The model is applied to two theoretical case studies: (i) A microbial electrolysis cell (MEC) for continuous anodic volatile fatty acids (VFA) oxidation and cathodic VFA reduction to alcohols, for which the theoretical system response to changes in applied voltage and VFA feed ratio (anode-to-cathode) as well as membrane type are investigated. This case involves multiple parallel electrode reactions in both anode and cathode compartments; (ii) A microbial fuel cell (MFC) for cathodic perchlorate reduction, in which the theoretical impact of feed flow rates and concentrations on the overall system performance are investigated. This case involves multiple electrode reactions in series in the cathode compartment. The model structure captures interactions between important system variables based on first principles and provides a platform for the dynamic description of METs involving electrode reactions both in parallel and in series and in both MFC and MEC configurations. Such a theoretical modelling approach, largely based on first principles, appears promising in the development and testing of MET control and optimization strategies., Competing Interests: The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

A series of previously published physiologically based pharmacokinetic (PBPK) models describe the effect of perchlorate on iodide uptake by the thyroid, with the mechanism being competitive inhibition of iodide transport by the sodium-iodide symporter (NIS). Hence a key parameter of these models is the affinity of perchlorate for the NIS, characterized as the Michaelis-Menten kinetic constant, K m . However, when model predictions were compared to published results of a human study measuring radio-iodide uptake (RAIU) inhibition after controlled perchlorate exposures, it was found to only fit the lowest exposure level and underpredicted RAIU inhibition at higher levels. Published in vitro data, in which perchlorate-induced inhibition of iodide uptake via the NIS was measured, were re-analyzed. K m for binding of perchlorate to the NIS originally derived from these data, 1.5 μm, had been obtained using Lineweaver-Burk plots, which allow for linear regression but invert the signal-noise of the data. Re-fitting these data by non-linear regression of the non-inverted data yielded a 60% lower value for the K m , 0.59 μm. Substituting this value into the PBPK model for an average adult human significantly improved model agreement with the human RAIU data for exposures <100 μg kg -1  day -1 . Thus, this lower K m value both fits the in vitro NIS kinetics and provides better predictions of human in vivo RAIU data. This change in K m increases the predicted sensitivity of humans to perchlorate over twofold for low-level exposures. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. Published 2016. This article is a U.S. Government work and is in the public domain in the USA., (Published 2016. This article is a U.S. Government work and is in the public domain in the USA.)