Sodium chlorite increases production of reactive oxygen species that impair the antioxidant system and cause morphological changes in human erythrocytes

Accumulation of nitrite after reclaimed water recharge due to the disinfection byproduct chlorite

Due to its toxicity, the disinfection byproduct chlorite in drinking water is strictly regulated to be ≤ 1.0 mg/L, but in reclaimed, non-drinking water chlorite is unregulated and rarely considered. However, chlorite is cytotoxic and has a high oxidation potential. Therefore, as reclaimed water infiltrates soil and groundwater, it may alter the soil environment and microbial community, which may affect the degradation of organic matter and the transformation of the N element. In this study, the effects of reclaimed water containing chlorite on soil microorganisms were investigated by simulating subsurface infiltration. It was found that chlorite improved the conversion of nitrate nitrogen to nitrite nitrogen, but inhibited further conversion of nitrite nitrogen. The nitrite nitrogen in the effluent reached 4.61 mg/L when chlorite was present, while only 0.16 mg/L was found in the control system. The chlorite produced obvious oxidative stress reactions in cells, inhibited the EPSs production, in which the contents of polysaccharides and proteins reduced by nearly 41% and 62%, respectively. Besides, chlorite resulted in the enrichment of efflux resistance genes in the microbial community, mainly adeF and cmlB1. Self-protection against chlorite is achieved mainly using efflux pump related genes. Metagenomics data analysis showed that Delftia became the dominant genus when exposed to chlorite, with the greatest abundance at 17.9%. Chlorite also resulted in the upregulated expression of nar genes (by more than 149%) and downregulation of nir gene expression (by more than 62%). This study reveals the effects of the disinfection byproduct chlorite on a soil microecosystem, providing important information for the management and reuse of reclaimed water.

A genetically encoded system for oxygen generation in living cells

Oxygen plays a key role in supporting life on our planet. It is particularly important in higher eukaryotes where it boosts bioenergetics as a thermodynamically favorable terminal electron acceptor and has important roles in cell signaling and development. Many human diseases stem from either insufficient or excessive oxygen. Despite its fundamental importance, we lack methods with which to manipulate the supply of oxygen with high spatiotemporal resolution in cells and in organisms. Here, we introduce a genetic system, SupplemeNtal Oxygen Released from ChLorite (SNORCL), for on-demand local generation of molecular oxygen in living cells, by harnessing prokaryotic chlorite O₂-lyase (Cld) enzymes that convert chlorite (ClO₂^-) into molecular oxygen (O₂) and chloride (Cl^-). We show that active Cld enzymes can be targeted to either the cytosol or mitochondria of human cells, and that coexpressing a chlorite transporter results in molecular oxygen production inside cells in response to externally added chlorite. This first-generation system allows fine temporal and spatial control of oxygen production, with immediate research applications. In the future, we anticipate that technologies based on SNORCL will have additional widespread applications in research, biotechnology, and medicine.

Kinetic and mechanistic understanding of chlorite oxidation during chlorination: Optimization of ClO2 pre-oxidation for disinfection byproduct control

Chlorine dioxide (ClO₂) applications to drinking water are limited by the formation of chlorite (ClO₂^-) which is regulated in many countries. However, when ClO₂ is used as a pre-oxidant, ClO₂^- can be oxidized by chlorine during subsequent disinfection. In this study, a kinetic model for the reaction of chlorine with ClO₂^- was developed to predict the fate of ClO₂^- during chlorine disinfection. The reaction of ClO₂^- with chlorine was found to be highly pH-dependent with formation of ClO₃^- and ClO₂ in ultrapure water. In presence of dissolved organic matter (DOM), 60-70% of the ClO₂^- was transformed to ClO₃^- during chlorination, while the in situ regenerated ClO₂ was quickly consumed by reaction with DOM. The remaining 30-40% of the ClO₂^- first reacted to ClO₂ which then formed chlorine from the DOM-ClO₂ reaction. Since only part of the ClO₂^- was transformed to ClO₃^-, the sum of the molar concentrations of oxychlorine species (ClO₂^- + ClO₃^-) decreased during chlorination. By kinetic modelling, the ClO₂^- concentration after 24 h of chlorination was accurately predicted in synthetic waters but was largely overestimated in natural waters, possibly due to a ClO₂^- decay enhanced by high concentrations of chloride and in situ formed bromine from bromide. Understanding the chlorine-ClO₂^- reaction mechanism and the corresponding kinetics allows to potentially apply higher ClO₂ doses during the pre-oxidation step, thus improving disinfection byproduct mitigation while keeping ClO₂^-, and if required, ClO₃^- below the regulatory limits. In addition, ClO₂ was demonstrated to efficiently degrade haloacetonitrile precursors, either when used as pre-oxidant or when regenerated in situ during chlorination.

Synergistic cytotoxicity of binary combinations of inorganic and organic disinfection byproducts assessed by real-time cell analysis

Chlorine, chlorine dioxide, and ozone are widely used as disinfectants in drinking water treatments. However, the combined use of different disinfectants can result in the formation of various organic and inorganic disinfection byproducts (DBPs). The toxic interactions, including synergism, addition, and antagonism, among the complex DBPs are still unclear. In this study, we established and verified a real-time cell analysis (RTCA) method for cytotoxicity measurement on Chinese hamster ovary (CHO) cell. Using this convenient and accurate method, we assessed the cytotoxicity of a series of binary combinations consisting of one of the 3 inorganic DBPs (chlorite, chlorate, and bromate) and one of the 32 regulated and emerging organic DBPs. The combination index (CI) of each combination was calculated and evaluated by isobolographic analysis to reflect the toxic interactions. The results confirmed the synergistic effect on cytotoxicity in the binary combinations consisting of chlorite and one of the 5 organic DBPs (2 iodinated DBPs (I-DBPs) and 3 brominated DBPs (Br-DBPs)), chlorate and one of the 4 organic DBPs (3 aromatic DBPs and dibromoacetonitrile), and bromate and one of the 3 organic DBPs (2 I-DBPs and dibromoacetic acid). The possible synergism mechanism of organic DBPs on the inorganic ones may be attributed to the influence of organic DBPs on cell membrane and cell antioxidant system. This study revealed the toxic interactions among organic and inorganic DBPs, and emphasized the latent adverse outcomes in the combined use of different disinfectants.

Isolation and characterization of a chlorate-reducing bacterium Ochrobactrum anthropi XM-1

A Gram-negative chlorate-reducing bacterial strain XM-1 was isolated. The 16S rRNA gene sequence identified the isolate as Ochrobactrum anthropi XM-1, which was the first strain of genus Ochrobactrum reported having the ability to reduce chlorate. The optimum growth temperature and pH for strain XM-1 to reduce chlorate was found to be 30 °C and 5.0-7.5, respectively, under anaerobic condition. Strain XM-1 could tolerate high chlorate concentration (200 mM), and utilize a variety of carbohydrates (glucose, L-arabinose, D-fructose, sucrose), glycerin and sodium citrate as electron donors. In addition, oxygen and nitrate could be used as electron acceptors, but perchlorate could not be reduced. Enzyme activities related to chlorate reducing were characterized in cell extracts. Activities of chlorate reductase and chlorite dismutase could be detected in XM-1 cells grown under both aerobic and anaerobic conditions, implying the two enzymes were constitutively expressed. This work suggests a high potential of applying Ochrobactrum anthropi XM-1 for remediation of chlorate contamination.

Organ-on-a-chip for assessing environmental toxicants

Man-made xenobiotics, whose potential toxicological effects are not fully understood, are oversaturating the already-contaminated environment. Due to the rate of toxicant accumulation, unmanaged disposal, and unknown adverse effects to the environment and the human population, there is a crucial need to screen for environmental toxicants. Animal models and in vitro models are ineffective models in predicting in vivo responses due to inter-species difference and/or lack of physiologically-relevant 3D tissue environment. Such conventional screening assays possess limitations that prevent dynamic understanding of toxicants and their metabolites produced in the human body. Organ-on-a-chip systems can recapitulate in vivo like environment and subsequently in vivo like responses generating a realistic mock-up of human organs of interest, which can potentially provide human physiology-relevant models for studying environmental toxicology. Feasibility, tunability, and low-maintenance features of organ-on-chips can also make possible to construct an interconnected network of multiple-organs-on-chip toward a realistic human-on-a-chip system. Such interconnected organ-on-a-chip network can be efficiently utilized for toxicological studies by enabling the study of metabolism, collective response, and fate of toxicants through its journey in the human body. Further advancements can address the challenges of this technology, which potentiates high predictive power for environmental toxicology studies.

Evaluation of OSMOCELLS, a new semi-automatic device for osmotic fragility assessment

INTRODUCTION

The osmotic fragility (OF) test was a central test for the diagnosis of hereditary red blood cell (RBC) disorders (mostly hereditary spherocytosis (HS), but thalassaemia as well). Nowadays although the traditional multitubes method has lost a prominent place, many laboratories still perform such a laboured test, despite the lack of standardization. In fact, the evaluation of OF may offer an inexpensive screening for RBC disorders. We present a new semi-automatic device, allowing the continuous recording of OF, by an updated dialysis method.

METHODS

Repeatability, stability over time, influence of the anticoagulant were evaluated among a population of healthy blood donors. The test was then performed among patients presenting inherited RBC disorders (HS or haemoglobinopathies) where OF is typically altered.

RESULTS

Repeatability was excellent; the parameters were greatly influenced by the nature of the anticoagulant and interestingly appeared stable for 48 h. Patients with RBC disorders displayed the expected profile in regard with their disease: patients with HS all presented an increased OF while patients with haemoglobinopathy displayed resistant profiles.

CONCLUSION

The device offers a substantial improvement in terms of standardization and consistency of the results and may offer a considerable gain for general laboratories.