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In modern conditions, providing the population with high-quality drinking water is becoming an increasingly urgent hygienic, scientific, technical, and social problem. Chlorine dioxide can be an alternative reagent for disinfecting drinking water. However, as with chlorine, dangerous by-products, particularly chlorites and chlorates are formed. The processes of development of morphofunctional changes in homeostasis remain insufficiently studied in this aspect. The objective is to determine the nature and peculiarities of changes in hematological indicators in the blood of animals due to the chronic impact of various concentrations of chlorates in drinking water to establish criteria for the hygienic assessment of their adverse effects on the body. The test animals were given drinking water with different concentrations of chlorates daily for 6 months: group 1 – control, group 2 – chlorates at a dose of 0.2 mg/dm³, group 3 – chlorates at a dose of 0.7 mg/dm³, and group 4 – chlorates at a dose of 1.2 mg/dm³. Evaluating the results of experimental studies, it should be noted that the most pronounced changes are observed in groups of animals that received chlorates in concentrations of 0.7 and 1.2 mg/dm³: a gradual decrease in the absolute number of leukocytes, the absolute and relative number of lymphocytes, relative to the indicators of the control group can be observed. In groups of animals that received chlorates in concentrations of 0.7 and 1.2 mg/dm³, a decrease in the absolute number of erythrocytes was observed during the 90 days of the experiment. It was established that the severity of the effects depended on the dose of chlorates and the time of exposure. Thus, the nature and features of changes in hematological indicators in the body of experimental animals during a chronic sanitary-toxicological experiment under the influence of chlorates in drinking water may indicate that chlorates affect the indicators of the blood system, being the indirect signs of disorders of other functional systems in the body, namely – slowing of redox reactions, hypoxic manifestations, reduction and weakening of the immune response and reactivity, etc.

Chlorate (ClO3-) is a common water pollutant due to its gigantic scale of production, wide applications in agriculture and industry, and formation as a toxic byproduct in various water treatment processes. This work reports on the facile preparation, mechanistic elucidation, and kinetic evaluation of a bimetallic catalyst for highly active ClO3- reduction into Cl-. Under 1 atm H2 and 20 °C, PdII and RuIII were sequentially adsorbed and reduced on a powdered activated carbon support, affording Ru0-Pd0/C from scratch within only 20 min. The Pd0 particles significantly accelerated the reductive immobilization of RuIII as >55% dispersed Ru0 outside Pd0. At pH 7, Ru-Pd/C shows a substantially higher activity of ClO3- reduction (initial turnover frequency >13.9 min-1 on Ru0; rate constant at 4050 L h-1 gmetal-1) than reported catalysts (e.g., Rh/C, Ir/C, Mo-Pd/C) and the monometallic Ru/C. In particular, Ru-Pd/C accomplished the reduction of concentrated 100 mM ClO3- (turnover number > 11,970), whereas Ru/C was quickly deactivated. In the bimetallic synergy, Ru0 rapidly reduces ClO3- while Pd0 scavenges the Ru-passivating ClO2- and restores Ru0. This work demonstrates a simple and effective design for heterogeneous catalysts tailored for emerging water treatment needs.

Chlorine is abundant in cells and biomolecules, yet the biology of chlorine oxidation and reduction is poorly understood. Some bacteria encode the enzyme chlorite dismutase (Cld), which detoxifies chlorite (ClO2-) by converting it to chloride (Cl-) and molecular oxygen (O2). Cld is highly specific for chlorite and aside from low hydrogen peroxide activity has no known alternative substrate. Here, we reasoned that because chlorite is an intermediate oxidation state of chlorine, Cld can be used as a biomarker for oxidized chlorine species. Cld was abundant in metagenomes from various terrestrial habitats. About 5% of bacterial and archaeal genera contain a microorganism encoding Cld in its genome, and within some genera Cld is highly conserved. Cld has been subjected to extensive horizontal gene transfer. Genes found to have a genetic association with Cld include known genes for responding to reactive chlorine species and uncharacterized genes for transporters, regulatory elements, and putative oxidoreductases that present targets for future research. Cld was repeatedly co-located in genomes with genes for enzymes that can inadvertently reduce perchlorate (ClO4-) or chlorate (ClO3-), indicating that in situ (per)chlorate reduction does not only occur through specialized anaerobic respiratory metabolisms. The presence of Cld in genomes of obligate aerobes without such enzymes suggested that chlorite, like hypochlorous acid (HOCl), might be formed by oxidative processes within natural habitats. In summary, the comparative genomics of Cld has provided an atlas for a deeper understanding of chlorine oxidation and reduction reactions that are an underrecognized feature of biology.

In modern conditions, providing the population with high-quality drinking water is becoming an increasingly urgent hygienic, scientific, technical, and social problem. Chlorine dioxide can be an alternative reagent for disinfecting drinking water. However, as with chlorine, dangerous by-products, particularly chlorites and chlorates are formed. The processes of development of morphofunctional changes in homeostasis remain insufficiently studied in this aspect. The objective is to determine the nature and peculiarities of changes in hematological indicators in the blood of animals due to the chronic impact of various concentrations of chlorates in drinking water to establish criteria for the hygienic assessment of their adverse effects on the body. The test animals were given drinking water with different concentrations of chlorates daily for 6 months: group 1 – control, group 2 – chlorates at a dose of 0.2 mg/dm³, group 3 – chlorates at a dose of 0.7 mg/dm³, and group 4 – chlorates at a dose of 1.2 mg/dm³. Evaluating the results of experimental studies, it should be noted that the most pronounced changes are observed in groups of animals that received chlorates in concentrations of 0.7 and 1.2 mg/dm³: a gradual decrease in the absolute number of leukocytes, the absolute and relative number of lymphocytes, relative to the indicators of the control group can be observed. In groups of animals that received chlorates in concentrations of 0.7 and 1.2 mg/dm³, a decrease in the absolute number of erythrocytes was observed during the 90 days of the experiment. It was established that the severity of the effects depended on the dose of chlorates and the time of exposure. Thus, the nature and features of changes in hematological indicators in the body of experimental animals during a chronic sanitary-toxicological experiment under the influence of chlorates in drinking water may indicate that chlorates affect the indicators of the blood system, being the indirect signs of disorders of other functional systems in the body, namely – slowing of redox reactions, hypoxic manifestations, reduction and weakening of the immune response and reactivity, etc. [ABSTRACT FROM AUTHOR]

Chlorates and perchlorates, inorganic salts known for their potent oxidizing properties, find utility in various products such as pyrotechnics, matches, and disinfectants. Their chemical properties also make them suitable for homemade explosives, resulting in their extensive use by criminals. Hence, the forensic analysis of these compounds is vital for investigating crimes involving their utilization. A wide array of analytical techniques is available for detecting and quantifying these substances, offering forensic investigators an extensive toolkit to effectively analyze and identify chlorates and perchlorates in various samples. Recent research highlights the potential for leveraging the information obtained from analyzing these materials, including for intelligence purposes. The future of forensic analysis in this domain lies in extracting additional information, such as source attribution, through methods like chemometrics, thereby enhancing forensic intelligence capabilities. [ABSTRACT FROM AUTHOR]

Introduction: depressive symptoms may develop in subclinical hypothyroidism and their presence usually facilitates recognition and the establishment of replacement treatment; however, recent studies have found no association between the two. Be-sides, thyroid function can be affected by endocrine disruptors and some of them, such as chlorates, can be found in the water we drink. Objectives: to know if the type of water consumed may influence the development of depressive symptoms in patients with subclinical hypothyroidism. Methods: 96 women with subclinical hypothyroidism, without thyroid treatment, par-ticipated from a health area in Spain. We studied, among other variables, the pres-ence of depressive symptoms, type of water consumption (tap, bottled or spring) and the level of chlorates in the tap water. Results: 41.7 % (40) of women presented depressive symptoms and these were relat-ed to the consumption of tap water (p = 0.001), resulting in a reliable predictor (OR, 27.79; p = 0.007). Chlorate level in the tap water was 250 µg/L, a value within the maximum limit allowed by law. Conclusions: chronic exposure to chlorates in water, in women with subclinical hypo-thyroidism, at levels authorized by law, could favor the inhibition of iodine transport and the appearance of depressive symptoms. It would be interesting to test this hy-pothesis as well as its possible effect on other population profiles. [ABSTRACT FROM AUTHOR]

The purpose of the work was to conduct a comparative scientific analysis of the main approaches to risk assessment and risk management to prevent the negative impact of drinking water on public health when treating it with chlorine dioxide in EU countries and Ukraine. The main risk to the population's health arising when consuming drinking water, is the risk of its microbiologicall contamination. Microbiological contamination of drinking water corresponds to a high risk, while the formation of disinfection byproducts in drinking water is an average risk. The regulatory documents of all EU countries take into account the requirements of Directive 2020/2184/EU regarding the content of chlorites and chlorates in drinking water when treating it with chlorine dioxide, while in Denmark, Slovakia, Hungary, Spain, and France, a risk-oriented approach to the safety of drinking water forced to introduce stricter standards for these indicators (as mandatory, recommended or those, which can be temporarily raised).The scientific analysis of the regulation of drinking water quality in the EU countries and Ukraine, as well as field studies on the safety and quality of drinking water at the Dnipro water station in the city of Kyiv, allowed to assess the risks of drinking water hazards and became the basis for raising the issue of revising or canceling the unscientific standard for chlorine dioxide in drinking water of the distribution network (≥0.1 mg/l), revising the strict standard for chlorites (≤0.2 mg/l), as well as control of drinking water quality by the content of chlorates following the requirements of European legislation. When appointing the organizers, executors, and decision-makers regarding risk assessment, similar approaches were implemented in various EU countries; in the documents of many countries, there are references to the relevant scientific institutions and the functions assigned to them. Under such conditions, the working programs of production control over drinking water quality and modernization plans can be adapted to the relevant water supply system and modern realities.

The purpose of the work was to conduct a comparative scientific analysis of the main approaches to risk assessment and risk management to prevent the negative impact of drinking water on public health when treating it with chlorine dioxide in EU countries and Ukraine. The main risk to the population's health arising when consuming drinking water, is the risk of its microbiologicall contamination. Microbiological contamination of drinking water corresponds to a high risk, while the formation of disinfection byproducts in drinking water is an average risk. The regulatory documents of all EU countries take into account the requirements of Directive 2020/2184/EU regarding the content of chlorites and chlorates in drinking water when treating it with chlorine dioxide, while in Denmark, Slovakia, Hungary, Spain, and France, a risk-oriented approach to the safety of drinking water forced to introduce stricter standards for these indicators (as mandatory, recommended or those, which can be temporarily raised).The scientific analysis of the regulation of drinking water quality in the EU countries and Ukraine, as well as field studies on the safety and quality of drinking water at the Dnipro water station in the city of Kyiv, allowed to assess the risks of drinking water hazards and became the basis for raising the issue of revising or canceling the unscientific standard for chlorine dioxide in drinking water of the distribution network (≥0.1 mg/l), revising the strict standard for chlorites (≤0.2 mg/l), as well as control of drinking water quality by the content of chlorates following the requirements of European legislation. When appointing the organizers, executors, and decision-makers regarding risk assessment, similar approaches were implemented in various EU countries; in the documents of many countries, there are references to the relevant scientific institutions and the functions assigned to them. Under such conditions, the working programs of production control over drinking water quality and modernization plans can be adapted to the relevant water supply system and modern realities. [ABSTRACT FROM AUTHOR]

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.

Soilless crop production is spread worldwide. It is a cultivating technique that enhances yield quality and quantity, thus contributing to both food safety and food security. However, in closed-loop soilless crops, the risk of spreading soil-borne pathogens through the recycled nutrient solution makes the establishment of a disinfection strategy necessary. In the current study, sodium hypochlorite was applied to the recycled nutrient solution as a chemical disinfectant to assess its impact on plant growth, leaf gas exchange, fruit yield, tissue mineral composition, and possible accumulation of chlorate and perchlorate residues in tomato fruits. The application of 2.5, 5, and 7.5 mg L−1 of chlorine three times at fortnightly intervals during the cropping period had no impact on plant growth or gas exchange parameters. Furthermore, the application of 2.5 mg L−1 of chlorine led to a significant increase in the total production of marketable fruits (total fruit weight per plant). No consistent differences in nutrient concentrations were recorded between the treatments. Moreover, neither chlorate nor perchlorate residues were detected in tomato fruits, even though chlorate residues were present in the nutrient solution. Therefore, the obtained tomatoes were safe for consumption. Further research is needed to test the application of chlorine in combination with crop inoculation with pathogens to test the efficiency of chlorine as a disinfectant in soilless nutrient solutions. [ABSTRACT FROM AUTHOR]

Dissimilatory perchlorate reduction is an anaerobic respiratory pathway that in communities might be influenced by metabolic interactions. Because the genes for perchlorate reduction are horizontally transferred, previous studies have been unable to identify uncultivated perchlorate-reducing populations. Here we recovered metagenome-assembled genomes from perchlorate-reducing sediment enrichments and employed a manual scaffolding approach to reconstruct gene clusters for perchlorate reduction found within mobile genetic elements. De novo assembly and binning of four enriched communities yielded 48 total draft genomes. In addition to canonical perchlorate reduction gene clusters and taxa, a new type of gene cluster with an alternative perchlorate reductase was identified. Phylogenetic analysis indicated past exchange between these gene clusters, and the presence of plasmids with either gene cluster shows that the potential for gene transfer via plasmid persisted throughout enrichment. However, a majority of genomes in each community lacked perchlorate reduction genes. Putative chlorate-reducing or sulfur-reducing populations were dominant in most communities, supporting the hypothesis that metabolic interactions might result from perchlorate reduction intermediates and byproducts. Other populations included a novel phylum-level lineage (Ca. Muirbacteria) and epibiotic prokaryotes with no known role in perchlorate reduction. These results reveal unexpected genetic diversity, suggest that perchlorate-reducing communities involve substantial metabolic interactions, and encourage expanded strategies to further understand the evolution and ecology of this metabolism.

Dairy processors in the Republic of Ireland have adopted chlorine-free chemicals for cleaning and chlorine gas for water disinfection as a means of minimizing chlorate residue in dairy products. For these "minimum chlorate technologies" to be satisfactory, they must be able to deliver product with acceptable levels of bacteria as well as minimum levels of chlorate and other chlorine-based residues. To establish the effectiveness of these technologies, sampling was conducted across the skim milk powder (SMP) manufacturing chain in 3 separate milk processing sites. Across the 3 sites a total of 11 different batches of SMP were sampled in duplicate from the whole milk silo through the manufacturing process to the powder product; yielding a total of 137 samples. Samples were tested for chlorate, perchlorate and trichloromethane alongside a suite of microbiological plate count tests including total bacteria, thermophilic bacteria, thermoduric bacteria and both mesophilic and thermophilic spore-forming bacteria. Chlorate was detected at reportable levels (≥0.01 mg/kg) in 9 of 22 SMP samples analyzed; resulting in a mean chlorate concentration 0.0183 mg/kg. Bacteria were ubiquitous across all samples analyzed with spore-forming bacteria counts ranging from 1.30 to 2.33 log cfu/g in SMP., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Genes important for growth of Pseudomonas stutzeri PDA on chlorate were identified using a randomly DNA bar-coded transposon mutant library. During chlorate reduction, mutations in genes encoding the chlorate reductase clrABC, predicted molybdopterin cofactor chaperon clrD, molybdopterin biosynthesis and two genes of unknown function (clrE, clrF) had fitness defects in pooled mutant assays (Bar-seq). Markerless in-frame deletions confirmed that clrA, clrB and clrC were essential for chlorate reduction, while clrD, clrE and clrF had less severe growth defects. Interestingly, the key detoxification gene cld was essential for chlorate reduction in isogenic pure culture experiments, but showed only minor fitness defects in Bar-seq experiments. We hypothesized this was enabled through chlorite dismutation by the community, as most strains in the Bar-seq library contained an intact cld. In support of this, Δcld grew with wild-type PDA or ΔclrA, and purified Cld also restored growth to the Δcld mutant. Expanding on this, wild-type PDA and a Δcld mutant of the perchlorate reducer Azospira suillum PS grew on perchlorate in co-culture, but not individually. These results demonstrate that co-occurrence of cld and a chloroxyanion reductase within a single organism is not necessary and raises the possibility of syntrophic (per)chlorate respiration in the environment.

Soilless crop production is spread worldwide. It is a cultivating technique that enhances yield quality and quantity, thus contributing to both food safety and food security. However, in closed-loop soilless crops, the risk of spreading soil-borne pathogens through the recycled nutrient solution makes the establishment of a disinfection strategy necessary. In the current study, sodium hypochlorite was applied to the recycled nutrient solution as a chemical disinfectant to assess its impact on plant growth, leaf gas exchange, fruit yield, tissue mineral composition, and possible accumulation of chlorate and perchlorate residues in tomato fruits. The application of 2.5, 5, and 7.5 mg L−1 of chlorine three times at fortnightly intervals during the cropping period had no impact on plant growth or gas exchange parameters. Furthermore, the application of 2.5 mg L−1 of chlorine led to a significant increase in the total production of marketable fruits (total fruit weight per plant). No consistent differences in nutrient concentrations were recorded between the treatments. Moreover, neither chlorate nor perchlorate residues were detected in tomato fruits, even though chlorate residues were present in the nutrient solution. Therefore, the obtained tomatoes were safe for consumption. Further research is needed to test the application of chlorine in combination with crop inoculation with pathogens to test the efficiency of chlorine as a disinfectant in soilless nutrient solutions.

UnlabelledDespite evidence for the prevalence of horizontal gene transfer of respiratory genes, little is known about how pathways functionally integrate within new hosts. One example of a mobile respiratory metabolism is bacterial chlorate reduction, which is frequently encoded on composite transposons. This implies that the essential components of the metabolism are encoded on these mobile elements. To test this, we heterologously expressed genes for chlorate reduction from Shewanella algae ACDC in the non-chlorate-reducing Shewanella oneidensis MR-1. The construct that ultimately endowed robust growth on chlorate included cld, a cytochrome c gene, clrABDC, and two genes of unknown function. Although strain MR-1 was unable to grow on chlorate after initial insertion of these genes into the chromosome, 11 derived strains capable of chlorate respiration were obtained through adaptive evolution. Genome resequencing indicated that all of the evolved chlorate-reducing strains replicated a large genomic region containing chlorate reduction genes. Contraction in copy number and loss of the ability to reduce chlorate were also observed, indicating that this phenomenon was extremely dynamic. Although most strains contained more than six copies of the replicated region, a single strain with less duplication also grew rapidly. This strain contained three additional mutations that we hypothesized compensated for the low copy number. We remade the mutations combinatorially in the unevolved strain and determined that a single nucleotide polymorphism (SNP) upstream of cld enabled growth on chlorate and was epistatic to a second base pair change in the NarP binding sequence between narQP and nrfA that enhanced growth.ImportanceThe ability of chlorate reduction composite transposons to form functional metabolisms after transfer to a new host is an important part of their propagation. To study this phenomenon, we engineered Shewanella oneidensis MR-1 into a chlorate reducer. We defined a set of genes sufficient to endow growth on chlorate from a plasmid, but found that chromosomal insertion of these genes was nonfunctional. Evolution of this inoperative strain into a chlorate reducer showed that tandem duplication was a dominant mechanism of activation. While copy number changes are a relatively rapid way of increasing gene dosage, replicating almost 1 megabase of extra DNA is costly. Mutations that alleviate the need for high copy number are expected to arise and eventually predominate, and we identified a single nucleotide polymorphism (SNP) that relieved the copy number requirement. This study uses both rational and evolutionary approaches to gain insight into the evolution of a fascinating respiratory metabolism.

We investigated perchlorate (ClO(4)(-)) and chlorate (ClO(3)(-)) (collectively (per)chlorate) in comparison with nitrate as potential inhibitors of sulfide (H(2)S) production by mesophilic sulfate-reducing microorganisms (SRMs). We demonstrate the specificity and potency of (per)chlorate as direct SRM inhibitors in both pure cultures and undefined sulfidogenic communities. We demonstrate that (per)chlorate and nitrate are antagonistic inhibitors and resistance is cross-inducible implying that these compounds share at least one common mechanism of resistance. Using tagged-transposon pools we identified genes responsible for sensitivity and resistance in Desulfovibrio alaskensis G20. We found that mutants in Dde_2702 (Rex), a repressor of the central sulfate-reduction pathway were resistant to both (per)chlorate and nitrate. In general, Rex derepresses its regulon in response to increasing intracellular NADH:NAD(+) ratios. In cells in which respiratory sulfate reduction is inhibited, NADH:NAD(+) ratios should increase leading to derepression of the sulfate-reduction pathway. In support of this, in (per)chlorate or nitrate-stressed wild-type G20 we observed higher NADH:NAD(+) ratios, increased transcripts and increased peptide counts for genes in the core Rex regulon. We conclude that one mode of (per)chlorate and nitrate toxicity is as direct inhibitors of the central sulfate-reduction pathway. Our results demonstrate that (per)chlorate are more potent inhibitors than nitrate in both pure cultures and communities, implying that they represent an attractive alternative for controlling sulfidogenesis in industrial ecosystems. Of these, perchlorate offers better application logistics because of its inhibitory potency, solubility, relative chemical stability, low affinity for mineral cations and high mobility in environmental systems.

UnlabelledThe pathways involved in aromatic compound oxidation under perchlorate and chlorate [collectively known as (per)chlorate]-reducing conditions are poorly understood. Previous studies suggest that these are oxygenase-dependent pathways involving O2 biogenically produced during (per)chlorate respiration. Recently, we described Sedimenticola selenatireducens CUZ and Dechloromarinus chlorophilus NSS, which oxidized phenylacetate and benzoate, two key intermediates in aromatic compound catabolism, coupled to the reduction of perchlorate or chlorate, respectively, and nitrate. While strain CUZ also oxidized benzoate and phenylacetate with oxygen as an electron acceptor, strain NSS oxidized only the latter, even at a very low oxygen concentration (1%, vol/vol). Strains CUZ and NSS contain similar genes for both the anaerobic and aerobic-hybrid pathways of benzoate and phenylacetate degradation; however, the key genes (paaABCD) encoding the epoxidase of the aerobic-hybrid phenylacetate pathway were not found in either genome. By using transcriptomics and proteomics, as well as by monitoring metabolic intermediates, we investigated the utilization of the anaerobic and aerobic-hybrid pathways on different electron acceptors. For strain CUZ, the results indicated utilization of the anaerobic pathways with perchlorate and nitrate as electron acceptors and of the aerobic-hybrid pathways in the presence of oxygen. In contrast, proteomic results suggest that strain NSS may use a combination of the anaerobic and aerobic-hybrid pathways when growing on phenylacetate with chlorate. Though microbial (per)chlorate reduction produces molecular oxygen through the dismutation of chlorite (ClO2(-)), this study demonstrates that anaerobic pathways for the degradation of aromatics can still be utilized by these novel organisms.ImportanceS. selenatireducens CUZ and D. chlorophilus NSS are (per)chlorate- and chlorate-reducing bacteria, respectively, whose genomes encode both anaerobic and aerobic-hybrid pathways for the degradation of phenylacetate and benzoate. Previous studies have shown that (per)chlorate-reducing bacteria and chlorate-reducing bacteria (CRB) can use aerobic pathways to oxidize aromatic compounds in otherwise anoxic environments by capturing the oxygen produced from chlorite dismutation. In contrast, we demonstrate that S. selenatireducens CUZ is the first perchlorate reducer known to utilize anaerobic aromatic degradation pathways with perchlorate as an electron acceptor and that it does so in preference over the aerobic-hybrid pathways, regardless of any oxygen produced from chlorite dismutation. D. chlorophilus NSS, on the other hand, may be carrying out anaerobic and aerobic-hybrid processes simultaneously. Concurrent use of anaerobic and aerobic pathways has not been previously reported for other CRB or any microorganisms that encode similar pathways of phenylacetate or benzoate degradation and may be advantageous in low-oxygen environments.

Two (per)chlorate-reducing bacteria, strains CUZ and NSS, were isolated from marine sediments in Berkeley and San Diego, CA, respectively. Strain CUZ respired both perchlorate and chlorate [collectively designated (per)chlorate], while strain NSS respired only chlorate. Phylogenetic analysis classified both strains as close relatives of the gammaproteobacterium Sedimenticola selenatireducens. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) preparations showed the presence of rod-shaped, motile cells containing one polar flagellum. Optimum growth for strain CUZ was observed at 25 to 30 °C, pH 7, and 4% NaCl, while strain NSS grew optimally at 37 to 42 °C, pH 7.5 to 8, and 1.5 to 2.5% NaCl. Both strains oxidized hydrogen, sulfide, various organic acids, and aromatics, such as benzoate and phenylacetate, as electron donors coupled to oxygen, nitrate, and (per)chlorate or chlorate as electron acceptors. The draft genome of strain CUZ carried the requisite (per)chlorate reduction island (PRI) for (per)chlorate respiration, while that of strain NSS carried the composite chlorate reduction transposon responsible for chlorate metabolism. The PRI of strain CUZ encoded a perchlorate reductase (Pcr), which reduced both perchlorate and chlorate, while the genome of strain NSS included a gene for a distinct chlorate reductase (Clr) that reduced only chlorate. When both (per)chlorate and nitrate were present, (per)chlorate was preferentially utilized if the inoculum was pregrown on (per)chlorate. Historically, (per)chlorate-reducing bacteria (PRB) and chlorate-reducing bacteria (CRB) have been isolated primarily from freshwater, mesophilic environments. This study describes the isolation and characterization of two highly related marine halophiles, one a PRB and the other a CRB, and thus broadens the known phylogenetic and physiological diversity of these unusual metabolisms.

Disinfection of drinking water is a fundamental step towards the protection of public health. Particularly, chlorine dioxide is one of the most important disinfection methods applied in public water systems. However, some unwanted and potentially toxic by-products (chlorite-ClO 2 - and chlorate-ClO 3 -) can be generated during this process. Thus, the European Union (EU) has recently set a permissible maximum concentration of 0.25 mg·L−1 for both ClO 2 - and ClO 3 - in the water intended for human consumption. Nevertheless, the existent strategies proposed for the elimination of these oxyanions present important limitations for their large-scale application. Here, we propose the ClO 2 - and ClO 3 - adsorption by two granulated activated carbons modified with five different alkyl quaternary ammonium-based surfactants, exhibiting a large affinity for inorganic anions. A granulated activated carbon modified with hexadecylpyridinium chloride monohydrate (CPC@CAG1) was selected as the most efficient adsorbent, achieving an excellent oxyanions removal (≥99 and 80 ± 0.5% of ClO 2 - and ClO 3 - in only 2 h, respectively). Finally, the ClO 2 - and ClO 3 - elimination was evaluated using a continuous flow under realistic conditions (drinking water from a real treatment plant and 12 min empty bed contact time (EBCT)), reaching a very high oxyanions removal efficacy for 4 cycles of 160 h-each, thus envisioning the future real application of this adsorbent in water disinfection treatments. • Cationic surfactant modified GAC exhibit a large affinity for inorganic anions. • Disinfection by-products elimination using real purified water from a DWTP. • ClO 2 - and ClO 3 - removal in the range of novel maximum permissible concentration set by the EU. • Easily available and abundant materials, and a techno-economically profitable process. [ABSTRACT FROM AUTHOR]

Previous work on respiratory chlorate reduction has biochemically identified the terminal reductase ClrABC and the chlorite detoxifying enzyme Cld. In Shewanella algae ACDC, genes encoding these enzymes reside on composite transposons whose core we refer to as the chlorate reduction composite transposon interior (CRI). To better understand this metabolism in ACDC, we used RNA-seq and proteomics to predict carbon and electron flow during chlorate reduction and posit that formate is an important electron carrier with lactate as the electron donor, but that NADH predominates on acetate. Chlorate-specific transcription of electron transport chain components or the CRI was not observed, but clr and cld transcription was attenuated by oxygen. The major chlorate-specific response related to oxidative stress and was indicative of reactive chlorine species production. A genetic system based on rpsL-streptomycin counter selection was developed to further dissect the metabolism, but ACDC readily lost the CRI via homologous recombination of the composite transposon's flanking insertion sequences. An engineered strain containing a single chromosomal CRI did not grow on chlorate, but overexpression of cld and its neighbouring cytochrome c restored growth. We postulate that the recently acquired CRI underwent copy-number expansion to circumvent insufficient expression of key genes in the pathway.

The paper analyzes the activity related to the production of weapons in the period between the end of the twenties and the early forties, in the electrochemical site of Bussi in Abruzzo. The Site was a strategic plant for the Italian government which productions were subjected to the strictest military secret. The plant was producing chemical weapons (phosgene and mustard gas) and super explosives such as the T4, the most powerful explosive in the world that together with the pentrite, always produced on site, were considered essential products for the defense of the Italian country. In particular, the T4 was produced for the first time in the plant with a process that was using only domestic raw materials, so an independent process that set Italy free from German imports. Additional military productions of interest of the Abruzzo's plant were the chlorate-based explosives for which it was initiated a completely new industrial cycle that boosted even further the capacities of Montecatini. Finally, in the paper we report the production of antiknock compound for fuels and the complex relationship between the Italian State (site of Bussi) the General Motor Chemical Company and the Du Pont de Nemours. [ABSTRACT FROM AUTHOR]

The genes for chlorate reduction in six bacterial strains were analyzed in order to gain insight into the metabolism. A newly isolated chlorate-reducing bacterium (Shewanella algae ACDC) and three previously isolated strains (Ideonella dechloratans, Pseudomonas sp. strain PK, and Dechloromarinus chlorophilus NSS) were genome sequenced and compared to published sequences (Alicycliphilus denitrificans BC plasmid pALIDE01 and Pseudomonas chloritidismutans AW-1). De novo assembly of genomes failed to join regions adjacent to genes involved in chlorate reduction, suggesting the presence of repeat regions. Using a bioinformatics approach and finishing PCRs to connect fragmented contigs, we discovered that chlorate reduction genes are flanked by insertion sequences, forming composite transposons in all four newly sequenced strains. These insertion sequences delineate regions with the potential to move horizontally and define a set of genes that may be important for chlorate reduction. In addition to core metabolic components, we have highlighted several such genes through comparative analysis and visualization. Phylogenetic analysis places chlorate reductase within a functionally diverse clade of type II dimethyl sulfoxide (DMSO) reductases, part of a larger family of enzymes with reactivity toward chlorate. Nucleotide-level forensics of regions surrounding chlorite dismutase (cld), as well as its phylogenetic clustering in a betaproteobacterial Cld clade, indicate that cld has been mobilized at least once from a perchlorate reducer to build chlorate respiration. Genome sequencing has identified, for the first time, chlorate reduction composite transposons. These transposons are constructed with flanking insertion sequences that differ in type and orientation between organisms, indicating that this mobile element has formed multiple times and is important for dissemination. Apart from core metabolic enzymes, very little is known about the genetic factors involved in chlorate reduction. Comparative analysis has identified several genes that may also be important, but the relative absence of accessory genes suggests that this mobile metabolism relies on host systems for electron transport, regulation, and cofactor synthesis. Phylogenetic analysis of Cld and ClrA provides support for the hypothesis that chlorate reduction was built multiple times from type II dimethyl sulfoxide (DMSO) reductases and cld. In at least one case, cld has been coopted from a perchlorate reduction island for this purpose. This work is a significant step toward understanding the genetics and evolution of chlorate reduction.

Wastewater polluted by organics can be treated by using electro-generated active chlorine, even if this promising route presents some important drawbacks such as the production of chlorinated by-products. Here, for the first time, this process was studied in a microfluidic electrochemical reactor with a very small inter-electrode distance (145 μm) using a water solution of NaCl and phenol and a BDD anode. The potential production of chloroacetic acids, chlorophenols, carboxylic acids, chlorate and perchlorate was carefully evaluated. It was shown, for the first time, up to our knowledge, that the use of the microfluidic device allows to perform the treatment under a continuous mode and to achieve higher current efficiencies and a lower generation of some important by-products such as chlorate and perchlorate. As an example, the use of the microfluidic apparatus equipped with an Ag cathode allowed to achieve a high removal of total organic carbon (about 76%) coupled with a current efficiency of 17% and the production of a small amount of chlorate (about 30 ppm) and no perchlorate. The effect of many parameters (namely, flow rate, current density and nature of cathode) was also investigated., 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 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Introduction: Introduction: depressive symptoms may develop in subclinical hypothyroidism and their presence usually facilitates recognition and the establishment of replacement treatment; however, recent studies have found no association between the two. Besides, thyroid function can be affected by endocrine disruptors and some of them, such as chlorates, can be found in the water we drink. Objectives: to know if the type of water consumed may influence the development of depressive symptoms in patients with subclinical hypothyroidism. Methods: 96 women with subclinical hypothyroidism, without thyroid treatment, were enrolled. We studied, among other variables, the presence of depressive symptoms, type of water consumption (tap, bottled or spring) and the level of chlorates in the tap water. Results: 41.7 % (40) of women presented depressive symptoms and these were related to the consumption of tap water (p = 0.001), resulting in a reliable predictor (OR, 27.79; p = 0.007). Chlorate level in the tap water was 250 µg/L, a value within the maximum limit allowed by law. Conclusions: chronic exposure to chlorates in water, in women with subclinical hypothyroidism, at levels authorized by law, could favor the inhibition of iodine transport and the appearance of depressive symptoms. It would be interesting to test this hypothesis as well as its possible effect on other population profiles.

A detailed and comprehensive study of the dynamics has been performed using quasiclassical trajectory calculations on a recent version of the ground 1 [sup 1]A[sup ′] potential energy surface (PES) [M. T. Martınez et al., Phys. Chem. Chem. Phys. 2, 589 (2000)] for this system. This PES was shown to account very well for the various experimental results available for the HOCl system. It has been found that this reaction occurs following different mechanisms depending on whether the HClO, HOCl, or both wells are visited in the course of the reaction. The different scalar and vector properties are strongly dependent on the type of mechanism through which a reaction takes place. Calculations have also been carried out to determine the distribution of collision times for each of the different mechanisms, and the time evolution of the differential cross section. For both reaction chemical channels the backward scattering is delayed with respect to the appearance of forward scattering. Although this reaction has been considered traditionally as an insertion reaction, it has been found that the first stages of the close interaction between the three atoms correspond to an attachment type of mechanism. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]