Selective survival of Escherichia coli phylotypes in freshwater beach sand

Comparative experiment to select water quality parameters for modelling the survival of Escherichia coli in lakes

Numerical health risk assessment models have been developed to describe faecal contamination of water using Escherichia coli as an indicator bacterium. Although many previously established numerical models for E. coli in aquatic environments have only considered the effects of one or two water quality parameters such as temperature and sunlight, it is difficult to simulate E. coli survival with only one or two parameters because the aquatic environment is a complex system. This study conducted a series of comparative experiments to select water quality parameters that should be preferentially considered in a numerical model for E. coli survival in lakes. The parameters considered were temperature, pH, dissolved oxygen (DO), total dissolved solids (TDS), suspended solids (SS), coexisting microbes, and light intensity. In the laboratory experiments, the survival of E. coli was observed by controlling two of these seven parameters, and the effects of these parameters on the rate of E. coli population change were statistically compared. Consequently, light intensity affected the survival of E. coli most significantly, followed by the presence of coexisting microbes, temperature, pH, and TDS. However, DO and SS had smaller effects on survival than other parameters. High-impact interactions on E. coli survival were observed between temperature and TDS and temperature and coexisting microbes. These results suggest that existing numerical models for simulating E. coli survival in lakes should be modified to consider the independent and interactive effects of multiple parameters such as sunlight, coexisting microbes, temperature, pH, and TDS.

Development of Multiplex RT qPCR Assays for Simultaneous Detection and Quantification of Faecal Indicator Bacteria in Bathing Recreational Waters

In this study, we designed and validated in silico and experimentally a rapid, sensitive, and specific multiplex RT qPCR for the detection and quantification of faecal indicator bacteria (FIB) used as microbiological references in marine bathing water regulations (Escherichia coli and intestinal enterococci). The 16S rRNA gene was used to quantify group-specific enterococci and Escherichia/Shigella and species-specific such as Enterococcus faecalis and E. faecium. Additionally, a ybbW gene encoding allantoin transporter protein was used to detect E. coli. An assessment of marine coastal systems (i.e., marine water and sediment) revealed that intestinal enterococci were the predominant group compared to Escherichia/Shigella. The low contribution of E. faecalis to the intestinal enterococci group was reported. As E. faecalis and E. faecium were reported at low concentrations, it is assumed that other enterococci of faecal origin are contributing to the high gene copy number of this group-specific enterococci. Moreover, low 16S rRNA gene copy numbers with respect to E. faecalis and E. faecium were reported in seawater compared to marine sediment. We conclude that marine sediments can affect the quantification of FIBs included in bathing water regulations. Valuing the quality of the marine coastal system through sediment monitoring is recommended.

Significant Factors for Modelling Survival of Escherichia coli in Lake Sediments

Currently available numerical models that describe the fecal contamination of aquatic environments using Escherichia coli as an indicator bacterium did not consider its survival in sediments. We conducted a series of comparative experiments to reveal the independent and interactive effects of sediment factors, including temperature, pH, water-extractable total dissolved solids (TDSs), coexisting microbes, and sampling sites, in lake environments on E. coli survival. In experiments, E. coli survival was observed by controlling any two factors at a time. Consequently, the decrease in pH and presence of coexisting microbes enhanced E. coli die-off, whereas the addition of water-extractable TDSs promoted its growth. To select factors to be considered for modelling E. coli survival in sediments, the independent effects of each factor and the interaction effect of the two factors were statistically compared based on their effect sizes (η2). As a result, pH (η2 = 59.5-89.0%) affected E. coli survival most significantly, followed by coexisting microbes (1.7-48.4%). Among the interactions affecting E. coli survival, including pH or coexisting microbes-which had larger independent effects-relatively larger statistically significant interactions were observed between pH and coexisting microbes (31.1%), coexisting microbes and water-extractable TDSs (85.4%), and coexisting microbes and temperature (26.4%).

Beach sand mycobiome: The silent threat of pathogenic fungi and toxic metal contamination for beachgoers

Emphasis is always placed on bacterial but not fungal pathogens in marine environments. We analysed the fungal diversity, functional predictions, and toxic metals and metalloids contamination in beach sand from different South African locations. Results revealed a diverse fungal community, with Ascomycota, Rozellomycota, and Basidiomycota being the dominant phyla. Functional predictions highlighted fungal metabolic pathways related to of carbohydrates, amino acids, and lipids, in different beach samples. Elevated concentrations of toxic metals and metalloids were detected in Central and Harbour beach sands, likely due to anthropogenic activities. Correlations among different elements were observed, suggesting complex interactions in the coastal environment. Fungal pathogens like Cladosporium, Fusarium, Aspergillus, and Candida in beach sands raise potential public health risk concerns. Therefore, monitoring fungal diversity (including pathogens) alongside bacterial contamination in beach environments is imperative. The results contribute to understanding fungal community dynamics, functional potential, toxic metal and metalloid contamination, and potential risks associated with beach sand ecosystems.

The behaviour of Escherichia coli and Pseudomonas aeruginosa in bottled mineral water

Microbial contamination of bottled water during the filling and capping procedure is a problem which should be avoided. The examination of the influence of carbon dioxide (CO2) on bacterial growth of Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) in bottled mineral water was the aim of this study. Commercially available glass bottles with plastic screw caps filled with natural mineral water (without additional CO2 "still" (StMW) and with CO2 "sparkling" (SpMW) were obtained from a manufacturer in the province of Styria, Austria. The artificial contamination was performed in the lab by opening the bottle with subsequent addition of a bacterial solution with a defined number of bacteria. For each bacterial strain, 12 bottles were prepared. Samples (100 mL) were taken after a specific number of days, filtrated and placed on Endo Agar for cultivation. After incubation for 24 h bacterial colonies were counted. In this study CO2 addition to bottled water reduced colony forming units of the two investigated bacterial strains over time.

Genetic Determinants of Escherichia coli Survival in Beach Sand

Escherichia coli contain a high level of genetic diversity and are generally associated with the guts of warm-blooded animals but have also been isolated from secondary habitats outside hosts. We used E. coli isolates from previous in situ microcosm experiments conducted under actual beach conditions and performed population-level genomic analysis to identify accessory genes associated with survival within the beach sand environment. E. coli strains capable of surviving had been selected for by seeding isolates originating from sand, sewage, and gull waste (n = 528; 176 from each source) into sand, which was sealed in microcosm chambers and buried for 45 days in the backshore beach of Lake Michigan. In the current work, survival-associated genes were identified by comparing the pangenome of viable E. coli populations at the end of the microcosm experiment with the original isolate collection and identifying loci enriched in the out put samples. We found that environmental survival was associated with a wide variety of genetic factors, with the majority corresponding to metabolism enzymes and transport proteins. Of the 414 unique functions identified, most were present across E. coli phylogroups, except B2 which is often associated with human pathogens. Gene modules that were enriched in surviving populations included a betaine biosynthesis pathway, which produces an osmoprotectant, and the GABA (gamma-aminobutyrate) biosynthesis pathway, which aids in pH homeostasis and nutrient use versatility. Overall, these results demonstrate that the genetic flexibility within this species allows for survival in the environment for extended periods. IMPORTANCE Escherichia coli is commonly used as an indicator of recent fecal pollution in recreational water despite its known ability to survive in secondary environments, such as beach sand. These long-term survivors from sand reservoirs can be introduced into the water column through wave action or runoff during precipitation events, thereby impacting the perception of local water quality. Current beach monitoring methods cannot differentiate long-term environmental survivors from E. coli derived from recent fecal input, resulting in inaccurate monitoring results and unnecessary beach closures. This work identified the genetic factors that are associated with long-term survivors, providing insight into the mechanistic basis for E. coli accumulation in beach sand. A greater understanding of the intrinsic ability of E. coli to survive long-term and conditions that promote such survival will provide evidence of the limitations of beach water quality assessments using this indicator.

Influence of Nutrients and the Native Community on E. coli Survival in the Beach Environment

Previous research has identified E. coli populations that persist in freshwater beach sand distinct from fecal pollution events. This work identifies factors that influence the survival of E. coli in sand using laboratory microcosms to replicate beach conditions. Microcosms were deployed to examine the effect of genetic background, competition with native microbial community, and increased nutrient concentrations on E. coli survival. Survival was comparable between the phylotypes B1 and B2, however, deficiency of stress response greatly reduced survival. In the absence of the native community under nutrient conditions comparable to those observed in sand, E. coli cell densities remained within an order of magnitude of initial concentrations after 5 weeks of incubation. Increased nitrogen was associated with decreased decay rates in the first 2 weeks, and increased carbon appeared to provide an advantage at later time points. However, the highest survival was found with the addition of both carbon and nitrogen. Native sand seeded with fresh Cladophora maintained higher concentrations of E. coli, compared to sand containing decayed Cladophora or no Cladophora. Our findings demonstrate persistent E. coli populations in sand can be affected by the availability of carbon and nitrogen, the ability to regulate stress, and the presence of algal mats (i.e., Cladophora). Further, this work suggests that the native microbial communities may modulate survival by outcompeting E. coli for nutrients. IMPORTANCE Current monitoring for fecal pollution does not account for persistent E. coli populations in freshwater sand, which can result in higher concentrations in water when no threat to human health is present. This work examined the drivers for persistent E. coli populations in sand to aid beach management techniques. We examined the influence of nutrients, including localized sources such as stranded Cladophora, on E. coli populations. We found the major determinant of E. coli survival in freshwater beach sand was the addition of nutrients, specifically carbon and nitrogen concentrations 10-fold higher than baseline concentrations on beaches. This work provides the framework for identifying pollution sources that can promote E. coli survival in sand through the characterization of carbon and nitrogen content, which can be incorporated into beach management techniques. Through this improved knowledge, we can begin to understand E. coli fluctuations in water due to resuspension from sand into water.