Interactions between Rotavirus and Natural Organic Matter Isolates with Different Physicochemical Characteristics

Interaction forces between rotavirus and Suwanee River natural organic matter (SRNOM) or Colorado River NOM (CRNOM) were studied by atomic force microscopy (AFM) in NaCl solutions and at unadjusted pH (5.7–5.9). Compared to CRNOM, SRNOM has more aromatic carbon and phenolic/carboxylic functional groups. CRNOM is characterized with aliphatic structure and considerable presence of polysaccharide moieties rich in hydroxyl functional groups. Strong repulsive forces were observed between rotavirus and silica or mica or SRNOM. The interaction decay length derived from the approaching curves for these systems involving rotavirus in high ionic strength solution was significantly higher than the theoretical Debye length. While no adhesion was observed for rotavirus and SRNOM, attraction was observed between CRNOM and rotavirus during approach and adhesion during retraction. Moreover, these adhesion forces decreased with increasing ionic strength. Interactions due to ionic hydrogen bonding between deprotonated carboxyl groups on rotavirus and hydroxyl functional groups on CRNOM were suggested as the dominant interaction mechanisms between rotavirus and CRNOM

Interactions between Rotavirus and Suwannee River Organic Matter: Aggregation, Deposition, and Adhesion Force Measurement

Interactions between rotavirus and Suwannee River natural organic matter (NOM) were studied by time-resolved dynamic light scattering, quartz crystal microbalance, and atomic force microscopy. In NOM-containing NaCl solutions of up to 600 mM, rotavirus suspension remained stable for over 4 h. Atomic force microscopy (AFM) measurement for interaction force decay length at different ionic strengths showed that nonelectrostatic repulsive forces were mainly responsible for eliminating aggregation in NaCl solutions. Aggregation rates of rotavirus in solutions containing 20 mg C/L increased with divalent cation concentration until reaching a critical coagulation concentration of 30 mM CaCl₂ or 70 mM MgCl₂. Deposition kinetics of rotavirus on NOM-coated silica surface was studied using quartz crystal microbalance. Experimental attachment efficiencies for rotavirus adsorption to NOM-coated surface in MgCl₂ solution were lower than in CaCl₂ solution at a given divalent cation concentration. Stronger adhesion force was measured for virus–virus and virus–NOM interactions in CaCl₂ solution compared to those in MgCl₂ or NaCl solutions at the same ionic strength. This study suggested that divalent cation complexation with carboxylate groups in NOM and on virus surface was an important mechanism in the deposition and aggregation kinetics of rotavirus

Mechanisms of MS2 Bacteriophage Removal by Fouled Ultrafiltration Membrane Subjected to Different Cleaning Methods

An ultrafiltration unit with a polyvinylidene fluoride (PVDF) membrane of 40 nm nominal pore size was used to study bacteriophage MS2 removal under different membrane conditions: pristine membrane, membrane fouled by soluble microbial product (SMP) extracted from membrane bioreactor (MBR) feedwater, backwashed membrane, and chemically cleaned membrane. The order of MS2 removal by these membranes was as follows: fouled membrane > backwashed membrane > chemically cleaned membrane ≈ pristine membrane. A linear correlation between membrane relative permeability and MS2 removal was found. Mass balance analysis showed a high percentage of MS2 in the concentrate for the fouled membrane as compared with the pristine membrane. Quartz crystal microbalance (QCM) results showed faster kinetics of MS2 adhesion to the pristine membrane than to the SMP-fouled membrane. In agreement with QCM results, an attractive force between MS2 and the pristine membrane was detected using an atomic force microscope (AFM), whereas a repulsive force was detected for the interaction between MS2 and the fouled membrane. The presence of SMP on the membrane surface led to higher rejection of MS2 due to both pore blocking and repulsion between MS2 and the SMP layer. Chemical cleaning removed most of the SMP foulant and as a result led to a lower MS2 removal

Inactivation Mechanisms of Human and Animal Rotaviruses by Solar UVA and Visible Light

Two rotavirus (RV) strains (sialidase-resistant Wa and sialidase-sensitive OSU) were irradiated with simulated solar UVA and visible light in sensitizer-free phosphate buffered solution (PBS) (lacking exogenous reactive oxygen species (ROS)) or secondary effluent wastewater (producing ROS). Although light attenuated for up to 15% through the secondary effluent wastewater (SEW), the inactivation efficacies increased by 0.7 log₁₀ for Wa and 2 log₁₀ for OSU compared to those in sensitizer-free phosphate buffered solution (PBS) after 4 h of irradiation. A binding assay using magnetic beads coated with porcine gastric mucin containing receptors for rotaviruses (PGM-MB) was developed to determine if inactivation influenced RV binding to its receptors. The linear correlation between the reduction in infectivity and the reduction in binding after irradiation in sensitizer-free solution suggests that the main mechanism of RV inactivation in the absence of exogenous ROS was due to damage to VP8*, the RV protein that binds to host cell receptors. For a given reduction in infectivity, greater damage in VP8* was observed with sialidase-resistant Wa compared to sialidase-sensitive OSU. The lack of correlation between the reduction in infectivity and the reduction in binding, in SEW, led us to include RNase treatment before the binding step to quantify virions with intact protein capsids and exclude virions that can bind to the receptors but have their capsid permeable after irradiation. This assay showed a linear correlation between the reduction in RV infectivity and RV–receptor interactions, suggesting that RV inactivation in SEW was due to compromised capsid proteins other than the VP8* protein. Thus, rotavirus inactivation by UVA and visible light irradiation depends on both the formation of ROS and the stability of viral proteins

Comparative Mammalian Cell Cytotoxicity of Wastewaters for Agricultural Reuse after Ozonation

Reusing wastewater in agriculture is becoming increasingly common, which necessitates disinfection to ensure reuse safety. However, disinfectants can react with wastewater constituents to form disinfection byproducts (DBPs), many of which are toxic and restrict the goal of safe reuse. Our objective was to benchmark the induction of mammalian cell cytotoxicity after ozonation against chlorination for three types of real wastewaters: municipal secondary effluent and two sources of minimally treated swine farm wastewaters. A new method to evaluate samples of suspected high cytotoxicity was devised. For the secondary effluent, ozonation reduced the cytotoxicity by as much as 10 times; chlorination lowered the cytotoxicity only when followed by dechlorination. The swine farm wastewaters were up to 2000 times more cytotoxic than the secondary effluent, and the highest reduction in cytotoxicity was 17 times as achieved by ozonation. These results indicate that secondary effluent is preferred over swine wastewaters for agricultural reuse regardless of the tested disinfectants. Ozonation consistently reduced the cytotoxicity of both the full strength and the organic extracts of all tested wastewaters more than chlorination. The only significant correlation was observed in the secondary wastewater between total haloacetonitriles and cytotoxicity. While the association of reduced toxicity with the modification or reduction of specific compound(s) is unclear, regulated DBPs may not be the primary forcing agents

Toxicity of Wastewater with Elevated Bromide and Iodide after Chlorination, Chloramination, or Ozonation Disinfection

Water reuse is receiving unprecedented attention as many areas around the globe attempt to better-manage their fresh water resources. Wastewaters in coastal regions may contain elevated levels of bromide (Br^–) and iodide (I^–) from seawater intrusion or high mineral content in the source waters. Disinfection of such wastewater is essential to prevent the spread of pathogens; however, little is known about the toxicity of the treated wastewater. In this study, we evaluated the genotoxicity to Chinese hamster ovary (CHO) cells induced by municipal secondary wastewater effluent amended with elevated Br^– and I^– after disinfection by chlorine, chloramines, or ozone. We calibrated and applied an <i>N</i>-acetylcysteine (NAC) thiol reactivity assay as a surrogate for thiol reactivity with biological proteins (glutathione) of wastewater samples. Chlorination of wastewaters produced CHO cell genotoxicity comparable to chloramination, 3.9 times more genotoxic than the nondisinfected controls. Ozonated wastewater was at least 3 times less genotoxic than the samples treated with chlorine-based disinfectants and was not significantly different compared with the nondisinfected controls. Positive and significant correlations were observed among genotoxicity, cytotoxicity, and NAC thiol reactivity for all disinfected samples. These results indicate that the ozonation of wastewater with high Br^– and I^– levels may yield organics with lower genotoxicity to CHO cells than chlorine-based disinfection. NAC thiol reactivity, although excluding the possible effect of bromate from ozonation in this work, could be used as a rapid <i>in chemico</i> screen for potential genotoxicity and cytotoxicity in mammalian cells exposed to disinfected wastewaters

Spectroscopic Indicators for Cytotoxicity of Chlorinated and Ozonated Effluents from Wastewater Stabilization Ponds and Activated Sludge

We investigated chronic mammalian cell cytotoxicity of wastewaters from four sources and their optical spectroscopic properties with or without chlorination or ozonation. Samples from effluents of activated sludge, nitrification tower, facultative waste stabilization pond, and maturation waste stabilization pond were either chlorinated or ozonated. The wastewater samples were analyzed for fluorescence excitation emission matrix, specific fluorescence index (SFI), and specific UV absorbance at 254 nm (SUVA). Before and after disinfection the wastewater samples were quantitatively analyzed for in vitro mammalian cell cytotoxicity. We found that the organic extracts from the ozonated samples induced lower cytotoxicity responses than those from the chlorinated or the nondisinfected samples. To develop correlations between SFI, SUVA, and cytotoxicity, we analyzed 21 independent samples. Significant linear correlations found among these samples suggest that under the tested conditions, cytotoxicity was preferentially influenced by the fluorescence and SUVA of their composite organic agents. These two spectroscopic parameters may be used as indicators for the potential cytotoxicity of nondisinfected, ozonated, or chlorinated municipal wastewaters

Table_4_Seasonal bleaching and partial mortality of Pocillopora verrucosa corals of the coast of central Vietnam.docx

IntroductionCoral reefs are one of the most productive yet vulnerable ecosystems on Earth. An important step in understanding the functioning of coral communities is studying the environmental impact on the state of reefs. The present study aimed to assess the impacts of the water temperature, precipitation, wave action, and population density on the seasonal bleaching, partial and complete mortality of shallow-water branching corals of Pocillopora verrucosa species complex. Materials and methodsThe present study was conducted at the Dam Bay research station (Nha Trang Bay) from 26 April 2020 to 2 April 2021. The environmental data was collected from the Dam Bay weather station and using a temperature logger planted on the nursery, coral bleaching and mortality were assessed visually using photos taken underwater. ResultsThroughout the study, the percentage of bleached coral colonies varied from 1 to 41.5% with two peaks, in autumn (October) and spring (April). Rates of the development of partial mortality varied from 0 to 10%, with a pronounced peak in December. At the end of the experiment, the percentage of coral colonies suffering from partial mortality reached 47%. Only 4,5% of experimental colonies died to the end of the study. Analysis revealed that water temperature and partial mortality are the drivers of bleaching, while wave action, temperature and bleaching are the factors with a significant impact on partial mortality.DiscussionThus, both bleaching and patrial mortality are interlinked and the effect of partial mortality on bleaching is stronger than the opposite. Both phenomena have pronounced seasonal variation, but their maximum manifestation does not coincide in time allowing corals to avoid their synergetic effect. Moreover, it was found that the impact of individual stress on mortality prevailed over the impact of seasonal bleaching and partial mortality events. The main cause of coral death was the development of algal fouling at the sites of colony lesions, which gradually spread over the entire surface of the colony.</p

Effect of Disinfectant Exposure on Legionella pneumophila Associated with Simulated Drinking Water Biofilms: Release, Inactivation, and Infectivity

Legionella pneumophila, the most commonly identified causative agent in drinking water associated with disease outbreaks, can be harbored by and released from drinking water biofilms. In this study, the release of biofilm-associated L. pneumophila under simulated drinking water flow containing a disinfectant residual was examined. Meanwhile, the inactivation and infectivity (to amoebae) of the released L. pneumophila were studied. To simulate drinking water system conditions, biofilms were prepared under either disinfectant exposure (predisinfected biofilms) or disinfectant-free (untreated biofilms) conditions, respectively. For experiments with water flow containing a disinfectant to release the biofilm-associated L. pneumophila from these two types of biofilms, the L. pneumophila release kinetics values from predisinfected and untreated biofilms under flow condition were not statistically different (one-way ANOVA, <i>p</i> > 0.05). However, inactivation of the L. pneumophila released from predisinfected biofilms was 1–2 times higher and amoeba infectivity was 2–29 times lower than that from untreated biofilms. The higher disinfectant resistance of L. pneumophila released from untreated biofilms was presumably influenced by the detachment of a larger amount of biofilm material (determined by 16S rRNA qPCR) surrounding the released L. pneumophila. This study highlights the interaction among disinfectant residual, biofilms, and L. pneumophila, which provides guidelines to assess and control pathogen risk

Partial least squares prediction model for the number of adsorbed viral particles on produce surfaces using six epicuticular physicochemical properties, including concentrations of alkanes, fatty acids, alcohols, and ketones, contact angle, and surface roughness.

<p>Partial least squares prediction model for the number of adsorbed viral particles on produce surfaces using six epicuticular physicochemical properties, including concentrations of alkanes, fatty acids, alcohols, and ketones, contact angle, and surface roughness.</p