Biological approaches for addressing the grand challenge of providing access to clean drinking water

Disruptive effects of sewage intrusion into drinking water: Microbial succession and organic transformation at molecular level

Drinking water distribution systems are increasingly vulnerable to sewage intrusion due to aging water infrastructure and intensifying water stress. While the health risks associated with sewage intrusion have been extensively studied, little is known about the impacts of intruded bacteria and dissolved organic matter (DOM) on microbiology in drinking water. In this dynamic study, we demonstrate that the intrusion of 1 % sewage into tap water resulted in immediate contamination, including an 8-fold increase in biomass (TCC), a 48.9 % increase in bacterial species (ASVs), a 12.5 % increase in organic carbon content (DOC), and a 13.5 % increase in unique DOM molecular formulae. Over time, sewage intrusion altered tap water microbiology by accelerating bacterial growth rates (5-fold faster), selectively promoting ASVs in community succession, and producing 998 more unique DOM formulae. More significantly, statistical analysis revealed that the intrusion of 1 % sewage shifted the driving force of bacterial and DOM composition covariance from a DOM-dependent process in tap water to a bacterial-governed process post-intrusion. Our results clearly demonstrate the disruptive effects of sewage intrusion into tap water, emphasizing the urgent need to consider the long-lasting impacts of sewage intrusion in drinking water distribution systems, in addition to its immediate health risks.

Potential risk of plant viruses entering disease cycle in surface water in protected vegetable growing areas of Eastern China

With the expansion of protected vegetable growing areas (PVGAs), viral plant diseases have become more prevalent, causing severe economic losses to the vegetable production industry in China. At present, researches on plant viruses mainly focus on plants, but there is only a few reports on the species of viruses in surface water from PVGAs. The surface water samples in PVGAs are representative to a certain extent, which has an important reference value for studying the characteristics of plant viruses in surface water. The purpose of this study was to identify the diversity and the possibility of entering disease infection cycle of plant viruses in water samples collected from PVGAs in eastern China. A total of 144 water samples were collected, and eight plant viruses including tobacco mosaic virus (TMV, 8.33%), cucumber green mottle mosaic virus (CGMMV, 33.33%), pepper mild mottle virus (PMMoV, 6.94%), cucumber mosaic virus (CMV, 0.69%), tomato masaic virus (ToMV, 3.47%), tomato mottle mosaic virus (ToMMV, 0.69%), tomato chlorosis virus (ToCV, 4.17%), and tomato yellow leaf curl virus (TYLCV, 5.56%) were examined using RT-PCR and PCR. The species of viruses in surface water varied greatly by location. CGMMV, TMV, ToCV, ToMV, ToMMV, and TYLCV were identified in Shandong, a northern part of Eastern China, whereas only PMMoV was found in Shanghai, a southern part of Eastern China. After healthy tobacco plants were inoculated with the concentrated solutions of TMV, ToMV, CGMMV, and PMMoV, could cause disease in healthy tobacco, indicating that the plant viruses in the concentrated solution have the infectivity, and the plant viruses in surface water have the possibility of entering the infection cycle of disease. The results will improve the understanding of the potential risks of waterborne disease transmission.

The Dark Side of Microbial Processes: Accumulation of Nitrate During Storage of Surface Water in the Dark and the Underlying Mechanism

In densely populated cities with limited land, storage of surface water in underground spaces is a potential solution to meet the rising demand of clean water. In addition, due to the imperative need of renewable solar energy and limited land resources, the deployment of floating solar photovoltaic (PV) systems over water has risen exponentially. In both scenarios, microbial communities in the water do not have access to sunlight. How the absence of sunlight influences microbial community function and the water quality is largely unknown. The objective of this study was to reveal microbial processes in surface water stored in the dark and water quality dynamics. Water from a freshwater reservoir was stored in the dark or light (control) for 6 months. Water quality was monitored at regular intervals. RNA sequencing was performed on the Illumina MiSeq platform and qPCR was used to substantiate the findings arising from the sequencing data. Our results showed that storage of surface water in the dark resulted in the accumulation of nitrate in the water. Storage in the dark promoted the decay of algal cells, increasing the amount of free nitrogen in the water. Most of the free nitrogen was eventually transformed into nitrate through microbial processes. RNA sequencing-based microbial community analyses and pure culture experiments using nitrifying bacteria Nitrosomonas europaea and Nitrobacter sp. revealed that the accumulation of nitrate in the dark was likely due to an increase in nitrification rate and a decrease in the assimilation rate of nitrate back into the biomass. IMPORTANCE Microbial communities play an essential role in maintaining a healthy aquatic ecosystem. For example, in surface water reservoirs, microorganisms produce oxygen, break down toxic contaminants and remove excess nitrogen. In densely populated cities with limited land, storing surface water in underground spaces and deploying floating solar photovoltaic (PV) systems over water are potential solutions to address water and energy sustainability challenges. In both scenarios, surface water is kept in the dark. In this work, we revealed how the absence of sunlight influences microbial community function and water quality. We showed that storage of surface water in the dark affected bacterial activities responsible for nitrogen transformation, resulting in the accumulation of nitrate in the water. Our findings highlight the importance of monitoring nitrate closely if raw surface water is to be stored in the dark and the potential need of downstream treatment to remove nitrate.

Differences in chlorine and peracetic acid disinfection kinetics of Enterococcus faecalis and Escherichia fergusonii and their susceptible strains based on gene expressions and genomics

This study was conducted to investigate mechanisms of cross-resistance to chlorine and peracetic acid (PAA) disinfectants by antibiotic-resistant bacteria. Our study evaluated chlorine and PAA based disinfection kinetics of erythromycin-resistant Enterococcus faecalis, meropenem-resistant Escherichia fergusonii, and susceptible strains of these species. Using the integrated second-order disinfectant decay model and first-order Chick-Watson's Law, it was found that the meropenem-resistant Escherichia fergusonii strain showed significantly less log inactivation compared to the susceptible E. fergusonii strain in response to both chlorine and PAA disinfection (p-value = 0.059, 3.5 × 10^-6). On the other hand, the susceptible Enterococcus faecalis strain showed similar log inactivation compared to the erythromycin-resistant strain in response to either treatment (p-value = 0.075, 0.28). Meropenem-resistant E. fergusonii showed an increase in gene expression of New Delhi metallo-β-lactamase (bla_NDM-1) gene to chlorine, but there was no increase in expression to PAA. Whole genome sequencing (WGS) was then conducted to elucidate the differences in genes among both resistant and susceptible table E. fergusonii strains. The average nucleotide identity (ANI) analysis of the draft genomes (>97% similarity) suggests that meropenem-resistant E. fergusonii (S1) and meropenem-susceptible E. fergusonii (S2) are the same species but different strains. Both strains have the same genes for oxidative stress pathways, oxidative scavenger genes, and nearly 40 different antibiotic efflux pump genes. The chromosomal and plasmid draft genomes of meropenem-resistant and susceptible E. fergusonii strains each have 65 and 52 antibiotic resistance genes, respectively. Of these, the resistant E. fergusonii strain harbored the extended-spectrum beta-lactamases bla_CTX-M-15 and bla_TEM-1 genes located on the chromosome, and a bla_TEM-1 gene on the plasmid. The overall findings of this study are significant, as they reveal that antibiotic-resistant and susceptible strains of E. fergusonii exhibit different responses towards chlorine and PAA disinfection.

The Effect of Environmental Values on German Primary School Students’ Knowledge on Water Supply

Permanent access to safe drinking water is guaranteed in most industrialized countries, while climate change is turning it into a serious global issue. Knowing how to use the valuable resource water consciously and sustainably requires well-informed and ecologically aware citizens. Environmental education approaches should help develop long-term environmental knowledge, pro-environmental attitudes, and behavior with the overall goal of promoting environmental citizenship. The present study, thus, examines the influence of environmental values on students’ environmental knowledge in a German primary school sample (9–10-year-old students) by providing an authentic, out-of-school learning experience on the topic of fresh water supply. Our approach goes beyond mere correlation analyses by using structural equation modeling (SEM) to measure effects between the two variables. Environmental values were monitored using the Two Major Environmental Values Model (2-MEV) with its two dimensions, Preservation and Utilization of nature. Following a quasi-experimental design, we assessed the learners’ knowledge before (T0), directly after (T1), and six weeks after (T2) module participation. Confirmatory factor analysis verified the two-factor-structure of the 2-MEV. Preservation turned out as a direct positive predictor of pre-knowledge (T0) but did not show any significant effect on post-knowledge (T1) and knowledge retention (T2). Utilization displayed a larger albeit negative direct effect on knowledge across all testing times, especially for pre- and post-knowledge. Our findings shed light on the significant impact of anthropocentric attitudes on knowledge acquisition within primary school samples and provided valuable insights into feasible environmental learning approaches.

A smartphone-based particle diffusometry platform for sub-attomolar detection of Vibrio cholerae in environmental water

Each year, 3.4 million people die from waterborne diseases worldwide. Development of a rapid and portable platform for detecting and monitoring waterborne pathogens would significantly aid in reducing the incidence and spread of infectious diseases. By combining optical methods and smartphone technology with molecular assays, the sensitivity required to detect exceedingly low concentrations of waterborne pathogens can readily be achieved. Here, we implement smartphone-based particle diffusometry (PD) detection of loop-mediated isothermal amplification (LAMP) targeting the waterborne pathogen Vibrio cholerae (V. cholerae). By measuring the diffusion of 400 nm streptavidin-coated fluorescent nanoparticles imaged at 68X magnification on a smartphone, we can detect as few as 6 V. cholerae cells per reaction (0.66 aM) in just 35 minutes. In a double-blinded study with 132 pond water samples, we establish a 91.8% sensitivity, 95.2% specificity, and 94.3% accuracy of the smartphone-based PD platform for detection of V. cholerae. Together, these results demonstrate the utility of this smartphone-based PD platform for rapid and sensitive detection of V. cholerae at the point of use.

Occurrence of Antibiotic-Resistant Bacteria and Genes in Two Drinking Water Treatment and Distribution Systems in the North-West Province of South Africa

With the increasing spread of antimicrobial resistance, there is growing attention to the contribution made by drinking water systems. The potential health impact of two drinking water treatment and distribution systems (A and B) in the North-West Province of South Africa was determined by investigating the water quality and occurrence of antimicrobial-resistant heterotrophic bacteria and genes in the raw and treated water over four seasons. Most of the physicochemical parameters except for electrical conductivity were within permissible limits. Coliform bacteria reduced from raw to potable water except for counts higher than the threshold recorded in Summer and Winter. A total of 203 heterotrophic bacterial isolates were recovered on chromogenic R2A medium and subjected to susceptibility testing to twelve antibiotics. Most of the isolates were resistant to β-lactam antibiotics and Trimethoprim, whereas they were susceptible to Ciprofloxacin, Erythromycin, and Neomycin. The proportions of Cephalothin and Kanamycin-resistant isolates were significantly higher (p < 0.05) after treatment for site A, compared to significantly lower β-lactam, Oxytetracycline, and Trimethoprim-resistant isolates for B. Over 50% of isolates were of high risk, indicating their origin from high antibiotic-use sources. Seventy-one (35%) isolates were multidrug-resistant, out of which the majority (53.5%, n = 38) possessed the strA gene, followed by strB 21 (29.6%), dfrB 13 (18.3%), aadA 11 (15.5%), bla_CTX-M 5 (7.0%), and tetA 3 (4.2%). The 16S rRNA gene sequences of the isolates revealed strains belonging to eight bacterial families, some of which are clinically important.

Green tea (Camellia sinensis) extract inhibits biofilm formation in acyl homoserine lactone-producing, antibiotic-resistant Morganella morganii isolated from Pasig River, Philippines

The drastic development of urban districts around the world has caused changes in the environment, specifically on metropolitan waterways such as the Pasig River in the Philippines. These significant changes resulted in diversity of microorganisms and their mechanisms employed such as antibiotic resistance and their communication system or quorum sensing (QS). In this study, four bacterial isolates from Pasig River, identified as Aeromonas salmonicida, Acinetobacter sp., Morganella morganii, and Citrobacter freundii, were observed to employ short-chain acyl homoserine lactone (AHL) as their signalling molecule based on in vitro assays using the biosensor strain Chromobacterium violaceum CV026. Furthermore, M. morganii isolate was shown to be resistant to chloramphenicol. This poses a significant threat not just to public health but also to the aquatic life present in the river. Thus, green tea (Camellia sinensis) extract was tested for its capability to inhibit in vitro biofilm formation in M. morganii, as well as the short-chain acyl homoserine lactone QS system using C. violaceum ATCC 12472. Results showed that the extract significantly (p < 0.05) inhibited biofilm formation in M. morganii at as low as 62.5 μg/mL (31.55%). Increasing the concentration (500 μg/mL) did not significantly (p > 0.05) enhance the activity (41.21%). Furthermore, the extract also inhibited pigmentation in C. violaceum ATCC 12472, suggesting QS inhibition. This study adds into record the production of short-chain AHLs by Aeromonas salmonicida, Acinetobacter sp., Morganella morganii, and Citrobacter freundii, as well as the potential of green tea extract as inhibitor of biofilm formation in antibiotic-resistant M. morganii possibly through QS inhibition.

Rise of the killer plants: investigating the antimicrobial activity of Australian plants to enhance biofilter-mediated pathogen removal

BACKGROUND

Biofilters are soil-plant based passive stormwater treatment systems which demonstrate promising, although inconsistent, removal of faecal microorganisms. Antimicrobial-producing plants represent a safe, inexpensive yet under-researched biofilter design component that may enhance treatment reliability. The mechanisms underlying plant-mediated microbial removal in biofilters have not been fully elucidated, particularly with respect to antimicrobial production. The aim of this study was therefore to inform biofilter vegetation selection guidelines for optimal pathogen treatment by conducting antimicrobial screening of biofilter-suitable plant species. This involved: (1) selecting native plants suitable for biofilters (17 species) in a Victorian context (southeast Australia); and (2) conducting antimicrobial susceptibility testing of selected plant methanolic extracts (≥ 5 biological replicates/species; 86 total) against reference stormwater faecal bacteria (Salmonella enterica subsp. enterica ser. Typhimurium, Enterococcus faecalis and Escherichia coli).

RESULTS

The present study represents the first report on the inhibitory activity of polar alcoholic extracts from multiple tested species. Extracts of plants in the Myrtaceae family, reputed for their production of antimicrobial oils, demonstrated significantly lower minimum inhibitory concentrations (MICs) than non-myrtaceous candidates (p < 0.0001). Melaleuca fulgens (median MIC: 8 mg/mL; range: [4-16 mg/mL]), Callistemon viminalis (16 mg/mL, [2-16 mg/mL]) and Leptospermum lanigerum (8 mg/mL, [4-16 mg/mL]) exhibited the strongest inhibitory activity against the selected bacteria (p < 0.05 compared to each tested non-myrtaceous candidate). In contrast, the Australian biofilter gold standard Carex appressa demonstrated eight-fold lower activity than the highest performer M. fulgens (64 mg/mL, [32-64 mg/mL]).

CONCLUSION

Our results suggest that myrtaceous plants, particularly M. fulgens, may be more effective than the current vegetation gold standard in mediating antibiosis and thus improving pathogen treatment within biofilters. Further investigation of these plants in biofilter contexts is recommended to refine biofilter vegetation selection guidelines.

Hydrographic parameters and distribution of dissolved Cu, Ni, Zn and nutrients near Jeddah desalination plant

The development of safe desalination plants with low environmental impact is as important an issue as the supply of drinking water. The desalination plant in Jeddah (Saudi Arabia, Red Sea coast) produces freshwater from seawater by multi-stage flash distillation (MSFD) and reverse osmosis (RO). The process produces brine as by-product, which is dumped into the sea. The aim of this study was to assess the impact of Jeddah desalination plant on the coastal water in the nearby of the plant. Total concentrations of dissolved Cu, Ni, Zn and nutrients in several locations around the plant were analyzed by cathodic stripping voltammetry. The average levels of dissolved Cu, Ni, and Zn on surface in the sampling locations were 15.02, 11.02, and 68.03 nM respectively, whereas the levels at the seafloor near the discharging point were much higher. Distribution of temperature, salinity, nutrients and dissolved oxygen were quite normal both on surface and in depth.

Macroinvertebrate communities in riverine systems of buffer areas of protected wildland, rangeland and city areas: implications for conservation of riverine systems on urbanising watersheds

Riverine systems in developing countries continue to be degraded by anthropogenic pressures such as urbanisation. The responses of biota in watersheds surrounding a drainage divide may provide critical information that is required to protect the ecological condition of riverine systems. This study assessed the spatial variation of selected environmental variables together with macroinvertebrate communities in upper reaches of riverine systems across different land use categories of the Bulawayo region. Based on an a priori selection criterion, studied sites were grouped following an urban-wastewater disturbance gradient comprising of (i) heavily polluted city sites, (ii) moderately disturbed rangeland sites and (iii) less disturbed sites of the buffer areas of protected wildland. Most of the studied environmental variables and the macroinvertebrate community assemblages were significantly (ANOVA, p < 0.05) different and degraded within the city areas. In this study, the variance of environmental variables known to be associated with organic pollution like increased nutrients, embeddedness by particulates, salinity, COD, conductivity, turbidity and reduced dissolved oxygen was found to be related with the variation of macroinvertebrate communities across the studied sites. Besides affirming the effectiveness of macroinvertebrate-based bioassessment approaches, the results of our study demonstrate that an aggressive riverine protection policy that prohibits the discharge of poor-quality urban effluents and preservation of the less disturbed riverine systems needs to be part of the larger urban planning and regulatory framework in urbanising watersheds.

Detection of antibiotic resistance, virulence gene determinants and biofilm formation in Aeromonas species isolated from cattle

This study aimed to assess the antibiogram of Aeromonas strains recovered from cattle faeces and the potential pathogenic status of the isolates. The antibiogram of the Aeromonas isolates demonstrated total resistance to clindamycin oxacillin, trimethoprim, novobiocin and ticarcillin. However, Aeromonas strains were sensitive to cefotaxime, oxytetracycline and tobramycin. The Aeromonas strains from Lovedale and Fort Cox farms were found to possess some virulence genes. The percentage distribution was aer 71.4%, ast 35.7%, fla 60.7%, lip 35.7% and hlyA 25% for Lovedale farm and aer 63.1%, alt 10.5%, ast 55.2%, fla 78.9%, lip 21% and hlyA 35.9% for Fort Cox farm. Class 1 integron was present in 27% of Aeromonas isolates; the bla TEM gene was present in 34.8%, while the blaP1 class A β-lactamase gene was detected in 12.1% of the isolates. Approximately 86% of the isolates formed a biofilm on microtitre plates. The presence of multiple antibiotic resistance and virulence genes in Aeromonas isolates from cattle faeces reveals the pathogenic and infectious importance of these isolates and is of great significance to public health. The possession of a biofilm-forming capability by such isolates may lead to difficulty during the management of infection related to Aeromonas species.

Identification of Viable Helicobacter pylori in Drinking Water Supplies by Cultural and Molecular Techniques

BACKGROUND

Helicobacter pylori is one of the most common causes of chronic bacterial infection in humans, directly related to peptic ulcer and gastric cancer. It has been suggested that H. pylori can be acquired through different transmission routes, including water. In this study, culture and qPCR were used to detect and identify the presence of H. pylori in drinking water. Furthermore, the combined techniques PMA-qPCR and DVC-FISH were applied for detection of viable cells of H. pylori.

RESULTS

Among 24 drinking water samples, 16 samples were positive for the presence of H. pylori, but viable cells were only detected in six samples. Characteristic colonies, covered by a mass of bacterial unspecific growth, were observed on selective agar plates from an only sample, after enrichment. The mixed culture was submitted to DVC-FISH and qPCR analysis, followed by sequencing of the amplicons. Molecular techniques confirmed the growth of H. pylori on the agar plate.

CONCLUSIONS

Our results demonstrate for the first time that H. pylori can survive and be potentially infective in drinking water, showing that water distribution systems could be a potential route for H. pylori transmission.

Optofluidic opportunities in global health, food, water and energy

Optofluidics is a rapidly advancing field that utilizes the integration of optics and microfluidics to provide a number of novel functionalities in microsystems. In this review, we discuss how this approach can potentially be applied to address some of the greatest challenges facing both the developing and developed world, including healthcare, food shortages, malnutrition, water purification, and energy. While medical diagnostics has received most of the attention to date, here we show that some other areas can also potentially benefit from optofluidic technology. Whenever possible we briefly describe how microsystems are currently used to address these problems and then explain why and how optofluidics can provide better solutions. The focus of the article is on the applications of optofluidic techniques in low-resource settings, but we also emphasize that some of these techniques, such as those related to food production, food safety assessment, nutrition monitoring, and energy production, could be very useful in well-developed areas as well.

Characterization of fibrous polymer silver/cobalt nanocomposite with enhanced bactericide activity

This manuscript describes the synthesis (based on the intermatrix synthesis (IMS) method), optimization, and application to bacterial disinfection of Ag@Co polymer-metal nanocomposite materials with magnetic and bactericidal properties. This material showed ideal bactericide features for being applied to bacterial disinfection of water, particularly (1) an enhanced bactericidal activity (when compared with other nanocomposites only containing Ag or Co nanoparticles), with a cell viability close to 0% for bacterial suspensions with an initial concentration below 10(5) colony forming units per milliliter (CFU/mL) after a single pass through the material, (2) capacity of killing a wide range of bacterial types (from coliforms to gram-positive bacteria), and (3) a long performance-time, with an efficiency of 100% (0% viability) up to 1 h of operation and higher than 90% during the first 24 h of continuous operation. The nanocomposite also showed a good performance when applied to water samples from natural sources with more complex matrices with efficiencies always higher than 80%.