Nora A. S. Hussain

Oil sands operations produce large quantities of oil sands process water (OSPW), which contains persistent and toxic naphthenic acids (NAs). In this study, ZnS with different Zn/S molar ratios was synthesized and evaluated for the first time for the degradation of a single model NA (5-phenyl valeric acid, PVA), a mixture of seven classical NAs, and natural NAs in real OSPW. ZnS with a 1:2 Zn/S ratio exhibited the highest PVA degradation (>93%), following pseudo-first-order kinetics (k = 0.319 h–1). The enhanced activity was attributed to increased surface area and pore volume, smaller crystalline size, and reduced bandgap energy. PVA degradation byproducts and pathways were also evaluated. ZnS effectively degraded structurally diverse NAs, with cyclohexanepentanoic acid (CHPA) and decanoic acid (DA) showing the highest efficiencies, likely due to their high carbon numbers (C10 and C11) and alkyl-branched linear structures. In real OSPW, fluorophore organic compounds (FOCs) with two and three fused rings showed >87% degradation, while approximately 60% of classical NAs (O2–NAs) were removed. Treatment also significantly reduced the immunotoxicity and cytotoxicity of OSPW. Overall, these findings demonstrate the potential of solar-assisted ZnS photocatalysis for treating naturally occurring NAs in industrially affected waters.

Cholera is a severe diarrheal disease caused by Vibrio cholerae, a natural inhabitant of brackish water. Effective control of cholera outbreaks depends on prompt detection of the pathogen from clinical specimens and tracking its source in the environment. Although the epidemiology of cholera is well studied, rapid detection of V. cholerae remains a challenge, and data on its abundance in environmental sources are limited. Here, we describe a sensitive molecular quantification assay by qPCR, which can be used on-site in low-resource settings on water without the need for DNA extraction. This newly optimized method exhibited 100% specificity for total V. cholerae as well as V. cholerae O1 and allowed detection of as few as three target CFU per reaction. The limit of detection is as low as 5 × 10³ CFU/L of water after concentrating biomass from the sample. The ability to perform qPCR on water samples without DNA extraction, portable features of the equipment, stability of the reagents at 4 °C and user-friendly online software facilitate fast quantitative analysis of V. cholerae. These characteristics make this assay extremely useful for field research in resource-poor settings and could support continuous monitoring in cholera-endemic areas.

Cholera is a severe diarrheal disease caused by Vibrio cholerae, a natural inhabitant of brackish water. Effective control of cholera outbreaks depends on prompt detection of the pathogen from clinical specimens and tracking its source in the environment. Although the epidemiology of chol-era is well studied, rapid detection of V. cholerae remains a challenge, and data on its abundance in environmental sources are limited. Here, we describe a sensitive molecular quantification as-say by qPCR, which can be used on-site in low resource settings directly on water without the need for DNA extraction. This newly optimized method exhibited 100% specificity for total V. cholerae as well as V. cholerae O1 and allowed detection of as few as three target genome copies per reaction. The limit of detection is as low as 5 × 10E3 genome copies/L of water after concentrat-ing biomass from the sample. The ability to perform qPCR directly on water samples, portable features of the equipment, stability of the reagents at 4°C and user-friendly online software facili-tate fast quantitative analysis of V. cholerae. These characteristics make this assay extremely use-ful for field research in resource-poor settings and could support continuous monitoring in cholera endemic areas.

Cholera continues to remain a major public health threat around the globe. Understanding the ecology, evolution, and environmental adaptation of the causative agent Vibrio cholerae and tracking the emergence of novel lineages with pathogenic potential are essential to combat the problem.

Vibrio metoecus is a recently described aquatic bacterium and opportunistic pathogen, closely related to and often coexisting with Vibrio cholerae. To study the relative abundance and population dynamics of both species in aquatic environments of cholera-endemic and cholera-free regions, we developed a multiplex qPCR assay allowing simultaneous quantification of total V. metoecus and V. cholerae (including toxigenic and O1 serogroup) cells. The presence of V. metoecus was restricted to samples from regions that are not endemic for cholera, where it was found at 20% of the abundance of V. cholerae. In this environment, non-toxigenic O1 serogroup V. cholerae represents almost one-fifth of the total V. cholerae population. In contrast, toxigenic O1 serogroup V. cholerae was also present in low abundance on the coast of cholera-endemic regions, but sustained in relatively high proportions throughout the year in inland waters. The majority of cells from both Vibrio species were recovered from particles rather than free-living, indicating a potential preference for attached versus planktonic lifestyles. This research further elucidates the population dynamics underpinning V. cholerae and its closest relative in cholera-endemic and non-endemic regions through culture-independent quantification from environmental samples.

Vibrio metoecusis a recently described and little studied causative agent of opportunistic infections in humans, often coexisting withV. choleraein aquatic environments. However, the relative abundance ofV. metoecuswithV. cholerae and their population dynamics in aquatic reservoirs is still unknown. We developed a multiplex qPCR assay with a limit of detection of three copies per reaction to simultaneously quantify totalV. metoecusandV. choleraeabundance, as well as the toxigenic and O1 serogroup subpopulations ofV. choleraefrom environmental samples. Four different genes were targeted as specific markers for individualVibriospecies or subpopulations;viuB, a gene encoding a vibriobactin utilization protein, was used to quantify the totalV. choleraepopulation. The cholera toxin genectxAprovided an estimation of toxigenicV. choleraeabundance, while therfbO1gene specifically detected and quantifiedV. choleraebelonging to the O1 serogroup, which includes almost all lineages of the species responsible for the majority of past and ongoing cholera pandemics. To measureV. metoecusabundance, the genemcp, encoding methyl accepting chemotaxis protein, was used. Marker specificity was confirmed by testing several isolates ofV. choleraeandV. metoecusalongside negative controls of isolates within and outside of theVibriogenus. Analysis of environmental water samples collected from four different geographic locations including cholera-endemic (Dhaka, Kuakata and Mathbaria in Bangladesh) and non-endemic (Oyster Pond in Falmouth, Massachusetts, USA) regions showed thatV. metoecuswas only present in the USA site, recurring seasonally. Within the coastal USA site, the non-toxigenic O1 serogroup represented up to ∼18% of the totalV. choleraepopulation.V. choleraetoxigenic O1 serogroup was absent or present in low abundance in coastal Bangladesh (Kuakata and Mathbaria) but constituted a relatively high proportion of the totalV. choleraepopulation sustained throughout the year in inland Bangladesh (Dhaka). A preference for host/particle attachment was observed, as the majority of cells from bothVibriospecies (>90%) were identified in the largest water size fraction sampled, composed of particles or organisms >63 μm and their attached bacteria. This is the first study to apply a culture-independent method to quantifyV. choleraeorV. metoecusdirectly in environmental reservoirs of areas endemic and non-endemic for cholera on significant temporal and spatial scales.SIGNIFICANCE: Cholera is a life-threatening disease that requires immediate intervention; it is of prime importance to have fast, accurate and sensitive means to detectV. cholerae. Consistent environmental monitoring of the abundance ofV. choleraealong with its toxigenic and O1 serogroup subpopulations could facilitate the determination of the actual distribution of this organism in aquatic reservoirs and thus help to predict an outbreak before it strikes. The lack of substantial temporal and spatial environmental sampling, along with specific quantitative measures, has made this goal elusive so far. The same is true forV. metoecus, a close relative ofV. choleraewhich has been associated with several clinical infections and could likely pose an emerging threat, readily exchanging genetic material with its more famous relative.