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The efficacy of SourceTracker software to attribute contamination from a variety of fecal sources spiked into ambient freshwater samples was investigated. Double-blinded samples spiked with ≤5 different sources (0.025–10% vol/vol) were evaluated against fecal taxon libraries characterized by next-generation amplicon sequencing. Three libraries, including an initial library (17 nonlocal sources), a blinded source library (5 local sources), and a composite library (local and nonlocal sources), were used with SourceTracker. SourceTracker’s predictions of fecal compositions in samples were made, in part, based on distributions of taxa within abundant genera identified as discriminatory by discriminant analyses but also using a large percentage of low abundance taxa. The initial library showed poor ability to characterize blinded samples, but, using local sources, SourceTracker showed 91% accuracy (31/34) at identifying the presence of source contamination, with two false positives for sewage and one for horse. Furthermore, sink predictions of source contamination were positively correlated (Spearman’s ρ ≥ 0.88, P< 0.001) with spiked source volumes. Using the composite library did not significantly affect sink predictions (P> 0.79) compared to those made using the local sources alone. Results of this study indicate that geographically associated fecal samples are required for SourceTracker to assign host sources accurately.

Biosand filters (BSFs) are point‐of‐use water treatment systems that can provide safe and affordable potable water to households in developing countries. However, little information is available on the dynamic performance of BSFs or for selecting local materials to use as filter media. In this study, water quality dynamics, biofilm characteristics, and hydraulic performance were investigated in two full‐scale BSFs. During four months of operation with sewage‐contaminated surface water, average log10removals of 1.7, 1.2, and 0.6 were observed for Escherichia coli, total coliforms, and total heterotrophs, respectively. Average removal efficiencies for turbidity, ultraviolet absorbance at 254 nm, and total organic carbon were 86, 36, and 27%, respectively. Dynamic analysis showed that significant removal of indicator organisms and total organic carbon occurred during the pause period between charging the BSFs. Biofilm characterization revealed that more particle‐associated biomass exists within the BSF column compared with the schmutzdecke layer.

Antimicrobial resistance (AMR) is a grand societal challenge with important dimensions in the water environment that contribute to its evolution and spread. Environmental monitoring could provide vital information for mitigating the spread of AMR; this includes assessing antibiotic resistance genes (ARGs) circulating among human populations, identifying key hotspots for evolution and dissemination of resistance, informing epidemiological and human health risk assessment models, and quantifying removal efficiencies by domestic wastewater infrastructure. However, standardized methods for monitoring AMR in the water environment will be vital to producing the comparable data sets needed to address such questions. Here we sought to establish scientific consensus on a framework for such standardization, evaluating the state of the science and practice of AMR monitoring of wastewater, recycled water, and surface water, through a literature review, survey, and workshop leveraging the expertise of academic, governmental, consulting, and water utility professionals.

Rapid isolation of Salmonellafrom food is essential for faster typing and source tracking in an outbreak. The objective of this study was to investigate a rapid isolation method that would augment the standard U.S. Food and Drug Administration's Bacteriological Analytical Manual(BAM) method. Food samples with low microbial load, including egg salad and ice cream, moderately high–microbial-load tomatoes, and high-microbial-load ground beef were intentionally inoculated with 2 to 48 CFU of Salmonella entericaserotype Typhimurium. The samples were preenriched in buffered peptone water for 6 h, and then selectively concentrated by immunomagnetic separation and plated for isolation on xylose-lysine-desoxycholate agar: the 6IX method. SalmonellaTyphimurium was presumptively identified from approximately 97% of the low-microbial-load and moderately high–microbial-load samples by the 6IX method 2 days before the BAM standard method for isolation of Salmonella. In 49% of the beef samples, SalmonellaTyphimurium was presumptively identified 1 or 2 days earlier by the 6IX method. Given the inocula used, our data clearly indicated that for most of the food samples tested, with the exception of ground beef, SalmonellaTyphimurium could be isolated two laboratory days earlier with the 6IX method compared with the BAM method. In conclusion, this 6IX method may expedite Salmonellaisolation and, therefore, has the potential to accelerate strain tracking for epidemiological analysis in a foodborne outbreak.

Prolyl oligopeptidase (POP) is widely distributed in mammals, where it is implicated in neuropeptide processing. It is also present in some bacteria and archaea. Because POP is found in mesophilic and hyperthermophilic organisms, and is distributed among all three phylogenetic domains, studies of its function and structure could lead to new insights about the evolution of enzyme mechanisms and thermostability. Kinetic studies were conducted on the POP of the hyperthermophilic archaeon Pyrococcus furiosus(Pfu) 85 °C in both H2O and D2O.PfuPOP displayed many similarities to mammalian POPs, however the solvent isotope effect (k0/k1) was 2.2 at both high and low pH, indicating that general base/acid catalysis is the rate-limiting step. The pH-rate profiles indicated a three-deprotonation process with pKavalues of 4.3, 7.2, and 9.1. The temperature dependence of these values revealed a heat of ionization of 4.7 kJ/mol for pKes1and 22 kJ/mol for pKes2, suggesting the catalytic involvement of a carboxyl group and an imidazole group, respectively. Temperature dependence of the catalytic rate was assessed at pH 6.0 and 7.6. Entropy values of −119 and −143 Jmol−1K−1were calculated at the respective pH values, with a corresponding difference in enthalpy of 8.5 kJ/mol. These values suggest that two or three hydrogen bonds are broken during the transition state of the acidic enzyme form, whereas only one or two are broken during the transition state of the basic enzyme form. A model has been constructed for PfuPOP based on the crystal structure of porcine POP and the sequence alignment. The similarities demonstrated for POPs from these two organisms reflect the most highly conserved characteristics of this class of serine protease, whereas the differences between these enzymes highlights the large evolutionary distance between them. Such fundamental information is crucial to our understanding of the function of proteins at high temperature.

Fecal microorganisms can enter water bodies in diverse ways, including runoff, sewage discharge, and direct fecal deposition. Once in water, the microorganisms experience conditions that are very different from intestinal habitats. The transition from host to aquatic environment may lead to rapid inactivation, some degree of persistence, or growth. Microorganisms may remain planktonic, be deposited in sediment, wash up on beaches, or attach to aquatic vegetation.