(Per)chlorate in Biology on Earth and Beyond.

Respiration of perchlorate and chlorate [collectively, (per)chlorate] was only recognized in the last 20 years, yet substantial advances have been made in our understanding of the underlying metabolisms. Although it was once considered solely anthropogenic, pervasive natural sources, both terrestrial and extraterrestrial, indicate an ancient (per)chlorate presence across our solar system. These discoveries stimulated interest in (per)chlorate microbiology, and the application of advanced approaches highlights exciting new facets. Forward and reverse genetics revealed new information regarding underlying molecular biology and associated regulatory mechanisms. Structural and functional analysis characterized core enzymes and identified novel reaction sequences. Comparative genomics elucidated evolutionary aspects, and stress analysis identified novel response mechanisms to reactive chlorine species. Finally, systems biology identified unique metabolic versatility and novel mechanisms of (per)chlorate respiration, including symbiosis and a hybrid enzymatic-abiotic metabolism. While many published studies focus on (per)chlorate and their basic metabolism, this review highlights seminal advances made over the last decade and identifies new directions and potential novel applications.

Development of Nickel- and Magnetite-Promoted Carbonized Cellulose Bead-Supported Bimetallic Pd-Pt Catalysts for Hydrogenation of Chlorate Ions in Aqueous Solution.

Cellulose grains were carbonized and applied as catalyst supports for nickel- and magnetite-promoted bimetallic palladium- and platinum-containing catalysts. The bimetallic spherical aggregates of Pd and Pt particles were created to enhance the synergistic effect among the precious metals during catalytic processes. As a first step, the cellulose bead-based supports were impregnated by nitrate salts of nickel and iron and carbonized at 973 K. After this step, the nickel was in an elemental state, while the iron was in a magnetite form in the corresponding supports. Then, Pd and Pt particles were deposited onto the supports and the catalyst surface; precious metal nanoparticles (10-20 nm) were clustered inside spherical aggregated particles 500-600 nm in size. The final bimetallic catalysts (i.e., Pd-Pt/CCB, Pd-Pt/Ni-CCB, and Pd-Pt/Fe3O4-CCB) were tested in hydrogenation of chlorate ions in the aqueous phase. For the nickel-promoted Pd-Pt catalyst, a >99% chlorate conversion was reached after 45 min at 80 °C. In contrast, the magnetite-promoted sample reached an 84.6% chlorate conversion after 3 h. Reuse tests were also carried out with the catalysts, and in the case of Pd-Pt/Ni-CCB after five cycles, the catalytic activity only decreased by ~7% which proves the stability of the system.

Growth and survival characteristics of Paucilactobacillus wasatchensis WDCO4.

Understanding characteristics that permit survival and growth of Paucilactobacillus wasatchensis as part of the nonstarter microbiota of cheese is important for minimizing unwanted gas formation in cheese that can cause downgrading because of slits and cracks. The ability of Plb. wasatchensis WDC04 to survive pasteurization was studied by inoculating raw milk with 108 cfu/mL and measuring survival after processing through a high-temperature, short-time pasteurizer. Extent and rate of growth of Plb. wasatchensis WDC04 as a function of pH, salt concentration, and presence of various organic acids were studied using 48-well microplates in an automated spectrophotometer measuring optical density at 600 nm. Better growth in the 1-mL wells was obtained when a micro-anaerobic environment (similar to that which occurs in cheese) was created by enzymically removing the oxygen. Faster growth occurred around neutral pH (pH 6 to 8) than at pH 5 (cheese pH), whereas only marginal growth occurred at pH 4. Adding sodium chloride retarded growth of Plb. wasatchensis WDC04, but slow growth occurred even at salt concentrations up to 6%. At salt-in-moisture (S/M) concentrations found in cheese, the rate of growth at 3.5% S/M >4.5% S/M >5.5% S/M. Thus, low salt level in cheese is a risk factor for Plb. wasatchensis growth during cheese storage and unwanted slits and cracks. Some of the organic acids tested (propionic, formic, and citric) tended to suppress growth of Plb. wasatchensis WDC04 more than would be expected from their effect on pH. No survival of Plb. wasatchensis WDC04 after pasteurization was observed with the reduction in numbers being 8 logs or more. Even subpasteurization heating at 69°C for 15 s was sufficient to inactivate Plb. wasatchensis WDC04, so its presence as part of the nonstarter microbiota of cheese should be considered as a postpasteurization environmental contamination.

Ultra-sonication for controlling the formation of disinfection by-products in the ClO2 pre-oxidation of water containing high concentrations of algae.

Eutrophication has become great concern in recent years due to the fact that rivers, lakes, and reservoirs are the main drinking water source. Studies have been performed to enhance the removal of algae with ClO2 pre-oxidation, but there was high potential in the formation of chlorite and chlorate. In this study, ultra-sonication was employed to assist algae removal and control disinfection by-products formation in ClO2 pre-oxidation processes. It was found that solo ultra-sonication for 10 min (algae removal 86.11 ± 2.16%) could achieve similar algae removal efficiency as that with solo ClO2 (0.5 mg/L) pre-oxidation for 10 min (algae removal 87.10 ± 3.50%). In addition, no formations of chlorite and chlorate were detected in solo ultra-sonication process. Five-minutes ultra-sonication followed by 5-min 0.5 mg/L ClO2 treatment (total treatment time 10 min; algae removal 93.55 ± 3.22%) provided a better performance on algae removal compared to the solo ClO2 (0.5 mg/L) pre-oxidation for 10 min. Moreover, chlorite was undetectable. It suggests that the utilization of ultra-sonication in ClO2 pretreatment for algae removal has highly prevented the formations of chlorite and chlorate.

Ion aggregation in high salt solutions. VII. The effect of cations on the structures of ion aggregates and water hydrogen-bonding network.

Ions in high salt solutions have a strong propensity to form polydisperse ion aggregates with broad size and shape distributions. In a series of previous comparative investigations using femtosecond IR pump-probe spectroscopy, molecular dynamics simulation, and graph theoretical analysis, we have shown that there exists a morphological difference in the structures of ion aggregates formed in various salt solutions. As salt concentration increases, the ions in high salt solutions form either cluster-like structures excluding water molecules or network-like structures entwined with water hydrogen-bonding networks. Interestingly, such morphological characteristics of the ion aggregates have been found to be in correlation with the solubility limits of salts. An important question that still remains unexplored is why certain salts with different cations have notably different solubility limits in water. Here, carrying out a series of molecular dynamics simulations of aqueous salt solutions and analyzing the distributions and connectivity patterns of ion aggregates with a spectral graph analysis method, we establish the relationship between the salt solubility and the ion aggregate morphology with a special emphasis on the cationic effects on water structures and ion aggregation. We anticipate that the understanding of large scale ion aggregate structures revealed in this study will be critical for elucidating the specific ion effects on the solubility and conformational stability of co-solute molecules such as proteins in water.

Chlorate adsorption from chlor-alkali plant brine stream.

Chlorates are present in the brine stream purged from chlor-alkali plants. Tests were conducted using activated carbon from coconut shell, coal or palm kernel shell to adsorb chlorate. The results show varying levels of adsorption with reduction ranging between 1.3 g/L and 1.8 g/L. This was higher than the chlorate generation rate of that plant, recorded at 1.22 g/L, indicating that chlorate can be adequately removed by adsorption using activated carbon. Coconut based activated carbon exhibited the best adsorption of chlorate of the three types of activated carbon tested. Introducing an adsorption step prior to purging of the brine will be able to reduce chlorate content in the brine stream. The best location for introducing the adsorption step was identified to be after dechlorination of the brine and before resaturation. Introduction of such an adsorption step will enable complete recovery of the brine and prevent brine purging, which in turn will result in less release of chlorides and chlorates to the environment.

Formation of Chlorination Byproducts and Their Emission Pathways in Chlorine Mediated Electro-Oxidation of Urine on Active and Nonactive Type Anodes.

Chlorination byproducts (CBPs) are harmful to human health and the environment. Their formation in chlorine mediated electro-oxidation is a concern for electrochemical urine treatment. We investigated the formation of chlorate, perchlorate, and organic chlorination byproducts (OCBPs) during galvanostatic (10, 15, 20 mA · cm(-2)) electro-oxidation of urine on boron-doped diamond (BDD) and thermally decomposed iridium oxide film (TDIROF) anodes. In the beginning of the batch experiments, the production of perchlorate was prevented by competing active chlorine and chlorate formation as well as by direct oxidation of organic substances. Perchlorate was only formed at higher specific charges (>17 Ah · L(-1) on BDD and >29 Ah · L(-1) on TDIROF) resulting in chlorate and perchlorate being the dominant CBPs (>90% of initial chloride). BDD produced mainly short chained OCBPs (dichloromethane, trichloromethane, and tetrachloromethane), whereas longer chained OCBPs (1,2-dichloropropane and 1,2-dichloroethane) were more frequently found on TDIROF. The OCBPs were primarily eliminated by electrochemical stripping: On BDD, this pathway accounted for 40% (dichloromethane) to 100% (tetrachloromethane) and on TDIROF for 90% (1,2-dichloroethane) to 100% (trichloromethane) of what was produced. A post-treatment of the liquid as well as the gas phase should be foreseen if CBP formation cannot be prevented by eliminating chloride or organic substances in a pretreatment.

Design of highly sensitive phosphorescence sensor for determination of procaterol hydrochloride based on inhibition of KClO3 oxidation fluorescein isothiocyanate.

Procaterol hydrochloride (Prh) can inhibit KClO3 oxidation of fluorescein isothiocyanate (FITC) to form a non-phosphorescent compound, which causes room temperature phosphorescence (RTP) of FITC in the system to enhance sharply the linear relationship between ∆Ip and the Prh content. Thus, a rapid response and highly sensitive phosphorescence sensor for the determination of Prh has been developed based on the inhibiting effect of Prh on KClO3 oxidation of FITC. This simple, high sensitivity (detection limit (LD) calculated by 3Sb /k was 0.019 fg/spot, sample volume 0.40 µl, corresponding concentration 4.8 × 10(-14) g ml(-1) ) and selective sensor with a wide linear range (0.080-11.20 g/spot) has been applied to detect Prh in blood samples, and the results were consistent with those obtained by high-performance liquid chromatography (HPLC). Simultaneously, the mechanism of the phosphorescence sensor for the detection of Prh was also investigated using infrared spectroscopy.

The origins of homochirality examined by using asymmetric autocatalysis.

Pyrimidyl alkanol was found to act as an asymmetric autocatalyst in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde. Asymmetric autocatalysis of 2-alkynylpyrimidyl alkanol with an extremely low enantiomeric excess (ca. 0.00005% ee) exhibits enormous asymmetric amplification to afford the same compound with >99.5% ee. This asymmetric autocatalysis with amplification of ee has been employed to examine the validity of proposed theories of the origins of homochirality. Circularly polarized light, quartz, sodium chlorate, cinnabar, chiral organic crystals and spontaneous absolute asymmetric synthesis were considered as possible candidates for the origin of chirality; each could act as a chiral source in asymmetric autocatalysis. Asymmetric autocatalysis can discriminate the isotope chirality arising from the small difference between carbon (carbon-13/carbon-12) and hydrogen (D/H) isotopes. Cryptochiral compounds were also discriminated by asymmetric autocatalysis.

Space asymmetry as a possible global feature.

A series of reports in the literature indicated symmetry breaking in assemblies of chiral molecules of opposite handedness. These unexpected observations could be accounted for as being generated by the "parity violation" of the nuclear weak force, combined with an autocatalytic amplification process. However, in many such cases, in particular of chiral fluids, this putative mechanism is far from providing a reasonable explanation for such discrimination. In this article it is suggested that space may have deviated a priori from absolute symmetry, a possibility which complies with observations in atoms and molecules and may even be implicated in the asymmetrical configuration of spiral galaxies. Space asymmetry can be extrapolated to a difference between the relative statistical weights of the "right" versus the "left" directions with respect to Euclidian coordinates or, analogously, to a difference between the clockwise and anticlockwise orientations in polar coordinates. The difference in weights of these directions in space is estimated to be around 1%, based on the differences observed in density values of chiral fluids and chiral crystals of NaClO3. The implied asymmetry of time, as the conjugated fourth dimension, suggests a similar difference in magnitude of the time coordinate in a right-handed versus left-handed space, which is feasible for experimental verification.

[Metabolism features of bacteria resistant to high concentrations of chromate].

Twenty strains of bacteria resistant to high concentrations of chromate were isolated from different ecological niches. They were able to reduce chromate to compounds of trivalent chromium--nonsoluble chromium hydroxide or soluble crystalline hydrates of trivalent chromium. The growth features of these microorganisms on media containing chromate at high concentrations (up to 20.0 g/l) are described. Besides chromate bacteria can reduce vanadate to compounds of V(4+) and Mo(6+) to Mo(5+). The best reduction takes place on the media where MPB. glucose or ethanol serves as the source of carbon. The growth and reduction of anion-in-study did not occur on organic acids. It was shown that tungstate, chlorate or perchlorate were not toxic for the studied bacteria up to concentrations of 10.0 g/l, however were not reduced by these microorganisms. The most active strains belong to genera Pseudomonas, Oerskovia, Bacillus, Micrococcus.

[Reduction of chlorate in the presence of heavy metals by Acinetobacter thermotoleranticus C-1].

Influence of heavy metals on Acinetobacter thermotoleranticus C-1 was studied by the rate of chlorate reduction and biomass growth. It was established that Fe3+ in a form of free ion at concentration of 30 mg/l also stimulates both the reduction of chlorate by A. thermotoleranticus C-1 and the growth of biomass, Cd2+ Pb2+ and Mn2+ do not practically affect the process velocity or stimulate it a little, Cu2+ and Zn2+ lower the reduction rate of C10(3)- 2.5-3 times, under these conditions the biomass growth is inhibited more weakly than the reduction rate. Nickel and cobalt in the mentioned amount inhibit completely the process of reduction. Metals in the form of hydroxide-ion proved to be less toxic for str. C-1, than their ion forms. General influence of a free ion, metal hydroxide and the amount of organic nutrition takes more considerable (stimulating or inhibiting) influence on the process, than each of these factors itself.

Preparation of 6-carboxyl chitin and its effects on cell proliferation in vitro.

This study concerns the performance evaluation of 6-carboxyl chitin for its wound healing application. 6-Carboxyl chitins were prepared by the oxidation of chitin at C-6 with NaClO/TEMPO/NaBr after α-chitin was pretreated in NaOH/urea solution. The products with different molecular weights were obtained by changing reaction conditions. They all were completely oxidized at C-6 and N-acetylated at C-2 according to FT-IR and NMR results. 6-Carboxyl chitins could stimulate significantly the proliferation of human skin fibroblasts (HSF) and human keratinocytes (HaCaT), and the bioactivities were concentration and Mws dependent. Within the scope of the study, 10-40 kDa of Mws and 10-100 µg/mL of concentrations were most suitable for the HSF proliferation, but the proliferation of HaCaT increased with decreasing the concentration and Mw. In addition, 6-carboxyl chitins could also induce macrophages and fibroblasts to secrete growth factors. Therefore, 6-carboxyl chitins could be expected to be an active ingredient for wound healing.

Effect of counterion binding efficiency on structure and dynamics of wormlike micelles.

We have studied the effect of counterion binding efficiency on the linear viscoelastic properties of wormlike micelles formed from hexadecyltrimethylammonium bromide (CTAB) in the presence of different nonpenetrating inorganic salts: potassium bromide (KBr), sodium nitrate (NaNO(3)), and sodium chlorate (NaClO(3)). We have varied the salt/surfactant ratio R at fixed surfactant concentration of 350 mM. Results are compared to data for the system cetylpyridinium chloride (CPyCl) and the penetrating counterion sodium salicylate (NaSal) (Oelschlaeger, C.; Schopferer, M.; Scheffold, F.; Willenbacher, N. Langmuir 2009, 25, 716-723). Mechanical high-frequency rheology and diffusing wave spectroscopy (DWS) based tracer microrheology are used to determine the shear moduli G' and G'' in the frequency range from 0.1 Hz up to 1 MHz (Willenbacher, N.; Oelschlaeger, C.; Schopferer, M.; Fischer, P.; Cardinaux, F.; Scheffold, F. Phys. Rev. Lett. 2007, 99, 068302, 1-4). This enables us to determine the plateau modulus G(0), which is related to the cross-link density or mesh size of the entanglement network, the bending stiffness kappa (also expressed as persistence length l(p) = kappa/k(B)T) corresponding to the semiflexible nature of the micelles, and the scission energy E(sciss), which is related to their contour length. The viscosity maximum shifts to higher R values, and the variation of viscosity with R is less pronounced as the binding strength decreases. The plateau modulus increases with R at low ionic strength and is constant around the viscosity maximum; the increase in G(0) at high R, which is presumably due to branching, is weak compared to the system with penetrating counterion. The scission energy E(sciss) approximately = 20 k(B)T is independent of counterion binding efficiency irrespective of R and is slightly higher compared to the system CPyCl/NaSal, indicating that branching may be significant already at the viscosity maximum in this latter case. The micellar flexibility increases with increasing binding efficiency of counterions according to the Hofmeister series. The persistence length values for systems CTAB/KBr, CTAB/NaNO(3), and CTAB/NaClO(3) are 40, 34, and 29 nm, respectively, independent of R, and are significantly higher than in the case of CPyCl/NaSal.

Natural chlorate in the environment: application of a new IC-ESI/MS/MS method with a Cl¹8O3-internal standard.

A new ion chromatography electrospray tandem mass spectrometry (IC-ESI/MS/MS) method has been developed for quantification and confirmation of chlorate (ClO3⁻) in environmental samples. The method involves the electrochemical generation of isotopically labeled chlorate internal standard (Cl¹8O3⁻) using ¹8O water (H2¹8O) he standard was added to all samples prior to analysis thereby minimizing the matrix effects that are associated with common ions without the need for expensive sample pretreatments. The method detection limit (MDL) for ClO3⁻ was 2 ng L⁻¹ for a 1 mL volume sample injection. The proposed method was successfully applied to analyze ClO3⁻ in difficult environmental samples including soil and plant leachates. The IC-ESI/MS/MS method described here was also compared to established EPA method 317.0 for ClO3⁻ analysis. Samples collected from a variety of environments previously shown to contain natural perchlorate (ClO4⁻) occurrence were analyzed using the proposed method and ClO3⁻ was found to co-occur with ClO4⁻ at concentrations ranging from < 2 ng L⁻¹ in precipitation from Texas and Puerto Rico to >500 mg kg⁻¹ in caliche salt deposits from the Atacama Desert in Chile. Relatively low concentrations of ClO3⁻ in some natural groundwater samples (0.1 µg L⁻¹) analyzed in this work may indicate lower stability when compared to ClO4⁻ in the subsurface. The high concentrations ClO3⁻ in caliches and soils (3-6 orders of magnitude greater) as compared to precipitation samples indicate that ClO3⁻, like ClO4⁻, may be atmospherically produced and deposited, then concentrated in dry soils, and is possibly a minor component in the biogeochemical cycle of chlorine.

[Markers of chloric acid (I) in biological systems--identification and properties]. / Markery kwasu chlorowego (I) w ukladach biologicznych--identyfikacja i wlasciwosci.

Reactive oxygen and nitrogen species are attributed to initiation and propagation of many diseases. The demonstration of elevated activity of myeloperoxidase and the level of 3-chlorotyrosine in atherosclerosis, kidney diseases and chronic inflammations brought about the interest in the biological role of another strong oxidant--hypochlorite. Concentration of this compound is extremely difficult to estimate in vivo and in vitro because of its high reactivity. The reaction of hypochlorite with biological compounds lead to formation of chlorohydrins, glutathione sulfonamides, chloramines, 3- and 3,5-dichlorotyrosines and chlorinated DNA bases (8-chloroadenine, 8-chloroguanine, 5-chlorocytosine and 5-chlorouracil). At least some of these products of hypochlorite action are believed to provide specific HOCl-biomarkers, useful especially in the analysis of clinical samples, using sensitive detection techniques.

[Reduction of chlorates by acinetobacter thermotoleranticus C-1 in the presence of chromate ions].

The rate of chlorate reduction by A. thermotoleranticus C-1 reached 59.6-63.7 mg/l an hour and did not practically depend on chlorate concentration in a broad range. Chlorate and chromate being jointly present in the medium, the rate of chlorate-reduction depended on chromate concentration and remained at the same level when content of chromate reached 5 mg/l. Under CrO4(2-) of 10.0 mg/l the reduction of chlorate by A. thermotoleranticus became inconsiderably slower. The increase of CrO4(2-) content to 20.0-30.0 mg/l decreased the chlorate reduction rate from 63.7 to 18.3-5.8 mg/l an hour, and availability of 50.0 mg/l of chromate was the inhibiting concentration for chlorate destruction and led to irreversible loss of the capacity ofA. thermotoleranticus C-1 to reduce chlorate. The reduction of chromate proceeded simultaneously with that of chlorate. The rate of chromate reduction by A. thermotoleranticus C-1 under their content in the medium of 3-20 mg/l was 0.5-0.37 mg/l an hour and decreased considerably with the increase of concentration of chromate-ions. Availability of chlorate had no effect on reduction of chromate by A. thermotoleranticus C-1.

[Metabolism peculiarities of bacteria restoring chlorates and perchlorates].

Bacteria facultative anaerobes capable to restore chlorine oxygen compounds - chlorates and perchlorates, using them as terminal acceptors of electrons, have been isolated from various natural sources. Chloride is the end product of this process. Besides chlorates and perchlorates the isolated bacteria also restored other electron acceptors: chromates, sulfates, nitrates, vanadates, manganates. The studied restored bacteria use awhole number of organic compounds as electron donors. The paper is presented in Russian.

[Chlorate reduction by immobilised bacteria in continuous conditions].

Chlorate reduction by the strain Aerococcus dechloraticans TGS-463 immobilized on the corncob under flow conditions has been studied. It has been established that under growth in the medium with chlorate the increase of the dilution rate (D) results in the lower efficacy of the process, i.e., a higher concentration of residual chlorates in the medium and a lower rate of chlorate reduction. The optimal D for chlorate reduction ranges from 1.12 to 1.5 hour(-1).

Reduction of bromate and chlorate contaminants in water using aqueous phase corona discharge.

This work demonstrates the ability of aqueous phase corona discharge to chemically reduce bromate and chlorate ions, common disinfection byproducts, to bromide and chloride ions, respectively. A high voltage pulse was applied to a needle electrode, submerged in the target solution, to generate highly reactive oxidative and reductive species in a temperature-controlled reactor. Optimal water matrix conditions were sought through changing the solution pH, temperature, and dissolved oxygen concentration. Additionally, several oxidative species scavengers were investigated, including methanol, ethanol, sucrose, and D-sorbitol. Chemical reduction rates were improved at low pH (3.5). The presence of dissolved oxygen significantly reduced the chemical reduction rate, and thus high solution temperature (50 °C) also achieved better chemical reduction. All oxidative species scavengers improved the chemical reduction rate; however, methanol and ethanol were superior as these compounds generate hydrogen bubbles in the presence of plasma, which deoxygenates the solution further improving the chemical reduction rate. The application of this technology to 30 µM bromate and chlorate solutions, under optimal water matrix conditions and with the addition of 72 g/L-COD methanol, achieved greater than 95% removal of the target compounds within 60 min. Increasing the initial concentration of the target compounds to 300 µM required 90 and 150 min to achieve similar chemical reductions for bromate and chlorate, respectively.