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Melamine-impregnated paper is made by impregnating paper with melamine-formaldehyde resin and can be hot-pressed and laminated onto the surface of wood boards. If the paper has antibacterial activity, it can prevent the spread of indoor bacteria, but impregnated paper with a long-term antibacterial effect has not been proposed. Metal–organic frameworks (MOFs) have been studied as a reservoir of metal ions. In this study, a silver-metal organic framework (Ag-BTC) was synthesized by a green and scalable method at 60 °C (A-60) and at room temperature (A-25). The structure and thermal stability of the Ag-BTC were characterized. Compared with A-25, the structure and particle size distribution of A-60 were more regular and uniform. The thermal stability and the compatibility of Ag-BTC and MF resin were suitable for hot-pressing process. Ag-BTC in the cured impregnated paper exhibited the sustained-release performance of Ag+. The antibacterial ratio of decorated blockboards with 0.10 wt% A-25 to E. coli and S. aureus exceeded 99.99%, reaching Level I antibacterial grade. Compared with A-60-decorated blockboards, the better antibacterial activity of A-25-decorated blockboards was due to the release of more Ag+. This study provides new ideas for the design of antibacterial melamine-impregnated paper. [ABSTRACT FROM AUTHOR]

Chitosan, a renowned natural polymer for its wide application, was exploited for industry paper coating solutions. This research aimed to investigate the antimicrobial and water vapor barrier of chitosan solution-coated industrymanufactured paper. The papers were obtained from a national company in Indonesia. The commercially available chitosan with three molecular weight levels (low, medium, and high) was solubilized in sodium acetate buffer and subsequently utilized as the coating solution. The other variable studied was the chitosan concentration in the coating solution, i.e., 1.0, 1.5, and 2.0% (w/w). The antimicrobial activity study was performed by testing against Gram-positive bacteria, represented by Staphylococcus aureus, and Gram-negative bacteria, represented by Escherichia coli. The low molecular weight chitosan showed the best antimicrobial activity and water vapor barrier performance. The 1 %w low molecular weight chitosan-coated paper had shown good antimicrobial activity, against both S. aureus and E. coli, with a growth reduction of > 95 %. The most effective antimicrobial activity against S. aureus was achieved by paper coated with a 1.5% solution of low molecular weight chitosan. For low molecular weight chitosan-coated paper the most effective water vapor barrier was exhibited at 1 %w chitosan concentration. Having shown the best water vapor barrier while maintaining good antimicrobial activity, the 1.0% solution of low molecular weight chitosan was appointed as the best coating solution in this research. [ABSTRACT FROM AUTHOR]

Wounds often develop infections caused by microbes. Preventing these microbes from causing infection is essential for wound healing. The current study therefore focuses on the preparation of an Fp (cellulose) scaffold coated with antimicrobial clindamycin drug (Cl) and chitosan (Cs) for use in wound dressings. Fp was used as a control. Before testing the efficacy of ClCFp scaffolds against bacterial strains and evaluating their cytocompatibility, they were thoroughly characterized using microscopic, spectroscopic, BET, and X-ray techniques. These methods confirmed coating of Cs and Cl drug on Fp. No significant structural damage to the Fp was observed. The porosity and surface area were found to decrease with coating. Invitro studies with HGF cells showed that the cells not only adhered to the scaffolds and proliferated, but also exhibited good viability. The results of the antibacterial tests showed that ClCFp scaffold was effective against both E. coli, "gram-negative" bacteria, and S. aureus, "gram-positive bacteria". Docking studies performed for the transcription termination factor Rho of E. coli and penicillin-binding protein 2 of S. aureus against the Cl drug confirmed the interaction between the Cl drug and bacterial proteins. Therefore, the ClCFp composite scaffolds have good prospects for biomedical applications and especially for wound dressings. [ABSTRACT FROM AUTHOR]

To the authors' knowledge, the role of restaurant menus as a vehicle for pathogens has not been explored. Menus, however, can pose as a vector for bacterial contamination and transfer. Sampling menus from two restaurants in the Houston, Texas, area showed the presence of up to 100 CFU/cm2 aerobic bacteria. Follow-up studies designed to investigate the ability of Salmonella and E. coli to persist on paper and laminated menus at various time points (0, 6, 24, 48, and 72 hours) demonstrated that bacteria persist more efficiently on laminated menus as compared to paper menus. Transfer studies performed to quantitatively determine the ability of bacteria to transfer from menus to fingertips and from fingertips to clean menus showed that bacteria can be transferred for up to 24 hours. The study described here showed that restaurant menus may serve as vehicles for pathogens and hence present a public health issue within the retail food environment.

[Display omitted] • A simple synthesis method has been developed for Ag@ZIF-8, involving controlling the loading and size of Ag NPs. • Ag@ZIF-8 meet the requirements for antibacterial agent used in the melamine-impregnated paper. • The multiple synergistic antibacterial mechanism of Ag@ZIF-8 was verified. • The decorated blockboards with 0.20 wt% Ag@ZIF-8 reached Level Ⅰ antibacterial grade. Melamine-impregnated paper, a decorative material in furniture and interior design, could potentially impede the spread of indoor bacteria if it possesses antibacterial properties. Here, nano Ag-doped ZIF-8 (Ag@ZIF-8) was synthesized using ion exchange and in-situ chemical reduction strategies, followed by incorporating it into melamine-impregnated paper. The ion exchange mechanism of Zn2+ and Ag+ during ion exchange reactions was investigated. The structure of Ag@ZIF-8 was well-defined, with Ag nanoparticles evenly distributed on the surface of ZIF-8. Ag@ZIF-8 showed good thermal stability at 400 °C, meeting the requirements for the hot-pressing process of the melamine-impregnated paper. Ag@ZIF-8 exhibited enhanced ROS generation under visible light compare to ZIF-8, which was attributed to its reinforced light absorption and charge carrier separation facilitated by the localized surface plasmon resonance (LSPR) effect. The antibacterial activity of Ag@ZIF-8 was better than ZIF-8, owing to the multiple-synergistic antibacterial mechanisms of the ion release and ROS generation. Specifically, the 10-Ag@ZIF-8 exhibited MIC of 128 μg/mL and 64 μg/mL against E. coli and S. aureus , respectively. The signal intensity of •O 2 − induced by 10-Ag@ZIF-8 was 4.38 times higher than that of ZIF-8. As the addition of Ag@ZIF-8 increased, the antibacterial performance of melamine-impregnated paper improved. Considering the antibacterial property and economy of melamine-impregnated paper, 0.20 wt% was the optimal amount for 10-Ag@ZIF-8 decorated blockboard. This study proposes a novel approach for synthesizing MOF-based melamine-impregnated paper with antibacterial properties, aiming to reduce bacterial spread, minimize disease risks, and contribute to lowering overall healthcare costs. [ABSTRACT FROM AUTHOR]

The transpeptidase (TP) activity of penicillin-binding proteins (PBPs), target of the beta-lactam antibiotics, is a well-validated antibacterial drug target. The TP activity of PBP1b converts un-cross-linked peptidoglycan to the cross-linked form. Directly measuring TP activity is difficult because cross-linked and un-cross-linked peptidoglycan have very similar chromatographic properties. The authors report a microdilution plate method to directly measure the TP enzyme activity, uncoupled from the transglycosylase (TG), for detection of TP inhibitors. Escherichia coli membranes were incubated with 100 mM ampicillin, followed by removal of unbound ampicillin. The substrate for the TP, un-cross-linked peptidoglycan, was prepared by incubating these membranes with peptidoglycan sugar precursors, 1 of which was radiolabeled. Subsequently, solubilized PBP1b was added and TP activity assayed. The cross-linked peptidoglycan formed was monitored by addition of wheat germ agglutinin scintillation proximity assay beads plus N-laurylsarcosine, which selectively captures cross-linked peptidoglycan. The PBP1bcatalyzed activity was inhibited by penicillin G but not by cephalexin or cephradine, which have higher affinity for PBP1a. Moenomycin, a TG inhibitor, also inhibited TP activity. Because this is a true enzyme assay, it has the potential to detect novel, non-beta-lactam TP inhibitors and could lead to the discovery of new antibacterial agents.

Class A high-molecular-weight penicillin-binding protein 1a (PBP1a) and PBP1b of Escherichia coli have both transglycosylase (TG) and transpeptidase (TP) activity. These enzymes are difficult to assay, since their substrates are difficult to prepare. We show the activity of PBP1a or PBP1b can be measured in membranes by cloning the PBP into an E. coli ponB::Spcr strain. Using this assay, we show that PBP1a is approximately 10-fold more sensitive to penicillin than PBP1b and that the 50% inhibitory concentration (IC50) of moenomycin, a TG inhibitor, is approximately 10-fold higher in the PBP transformants than in wild-type membranes; this increase in IC50 in transformants can be used to test the specificity of test compounds for inhibition of the TG. Alternatively, the coupled TG-TP activity of PBP1b can be directly measured in a two-step microplate assay. In the first step, radiolabeled lipid II, the TG substrate, was made in membranes of the E. coli ponB::Spcr strain by incubation with the peptidoglycan sugar precursors. In the second step, the TG-TP activity was assayed by adding a source of PBP1b to the membranes. The coupled TG-TP activity converts lipid II to cross-linked peptidoglycan, which was specifically captured by wheat germ agglutinin-coated scintillation proximity beads in the presence of 0.2% Sarkosyl (B. Chandrakala et al., Antimicrob. Agents Chemother. 48:30-40, 2004). The TG-TP assay was inhibited by penicillin and moenomycin as expected. Surprisingly, tunicamycin and nisin also inhibited the assay, and paper chromatography analysis revealed that both inhibited the transglycosylase. The assay can be used to screen for novel antibacterial agents.

In order to determine desiccation tolerances of bacterial strains, the survival of 58 diarrheagenic strains (18 salmonellae, 35 Shiga toxin-producing Escherichia coli [STEC], and 5 shigellae) and of 15 nonpathogenic E. coli strains was determined after drying at 35 degrees C for 24 h in paper disks. At an inoculum level of 10(7) CFU/disk, most of the salmonellae (14/18) and the STEC strains (31/35) survived with a population of 10(3) to 10(4) CFU/disk, whereas all of the shigellae (5/5) and the majority of the nonpathogenic E. coli strains (9/15) did not survive (the population was decreased to less than the detection limit of 10(2) CFU/disk). After 22 to 24 months of subsequent storage at 4 degrees C, all of the selected salmonellae (4/4) and most of the selected STEC strains (12/15) survived, keeping the original populations (10(3) to 10(4) CFU/disk). In contrast to the case for storage at 4 degrees C, all of 15 selected strains (5 strains each of Salmonella spp., STEC O157, and STEC O26) died after 35 to 70 days of storage at 25 degrees C and 35 degrees C. The survival rates of all of these 15 strains in paper disks after the 24 h of drying were substantially increased (10 to 79 times) by the presence of sucrose (12% to 36%). All of these 15 desiccated strains in paper disks survived after exposure to 70 degrees C for 5 h. The populations of these 15 strains inoculated in dried foods containing sucrose and/or fat (e.g., chocolate) were 100 times higher than those in the dried paper disks after drying for 24 h at 25 degrees C.

MurG and MraY, essential enzymes involved in the synthesis of bacterial peptidoglycan, are difficult to assay because the substrates are lipidic and hard to prepare in large quantities. Based on the use of Escherichia coli membranes lacking PBP1b, we report a high-throughput method to measure the activity of MurG and, optionally, MraY as well. In these membranes, incubation with the two peptidoglycan sugar precursors results in accumulation of lipid II rather than the peptidoglycan produced by wild-type membranes. MurG was assayed by addition of UDP-[3H]N-acetylglucosamine to membranes in which lipid I was preformed by incubation with UDP-N-acetyl-muramylpentapeptide, and the product was captured by wheat germ agglutinin scintillation proximity assay beads. In a modification of the assay, the activity of MraY was coupled to that of MurG by addition of both sugar precursors together in a single step. This allows simultaneous detection of inhibitors of either enzyme. Both assays could be performed using wild-type membranes by addition of the transglycosylase inhibitor moenomycin. Nisin and vancomycin inhibited the MurG reaction; the MraY-MurG assay was inhibited by tunicamycin as well. Inhibitors of other enzymes of peptidoglycan synthesis--penicillin G, moenomycin, and bacitracin--had no effect. Surprisingly, however, the beta-lactam cephalosporin C inhibited both the MurG and MraY-MurG assays, indicating a secondary mechanism by which this drug inhibits bacterial growth. In addition, it inhibited NADH dehydrogenase in membranes, a hitherto-unreported activity. These assays can be used to screen for novel antibacterial agents.

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Aqueous two-phase systems (ATPSs) have been widely utilized for liquid-liquid extraction and purification of biomolecules, with some studies also demonstrating their capacity as a biomarker concentration technique for use in diagnostic settings. As the limited polarity range of conventional polymer-based ATPSs can restrict their use, ionic liquid (IL)-based ATPSs have been recently proposed as a promising alternative to polymer-based ATPSs, since ILs are regarded as tunable solvents with excellent solvation capabilities for a variety of natural compounds and proteins. This study demonstrates the first application of IL ATPSs to point-of-care diagnostics. ATPSs consisting of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) and sodium phosphate salt were utilized to quickly concentrate biomarkers prior to detection using the lateral-flow immunoassay (LFA). We found the phase separation speed of the IL ATPS to be very rapid and a significant improvement upon the separation speed of both polymer-salt and micellar ATPSs. This system was successfully applied to both sandwich and competitive LFA formats and enhanced the detection of both Escherichia coli bacteria and the transferrin protein up to 8- and 20-fold, respectively. This system's compatibility with a broad range of biomolecules, rapid phase separation speed, and tunability suggest wide applicability for a large range of different antigens and biomarkers.

Monitoring of indicator organisms is conducted to assess potential risk of pathogen exposure from freshwaters such as recreational waters and drinking water sources. Total coliforms, fecal coliforms, Escherichia coli and enterococci are the most commonly measured indicator organisms. Their presence can indicate the potential presence of fecally transmitted pathogens. In Wisconsin, E. coli are used for determining potential human health risk in recreational waters. However, it has been shown that E. coli can survive and reproduce in a variety of aquatic environments, including in the activated sludge process of paper mills. Previous monitoring in a river in Wisconsin receiving paper mill effluent indicated that the mill was contributing to elevated E. coli levels that could affect the number of closings at a public beach located downstream from the mill. The goal of this study was to understand the public health implications of the E. coli at the beach. Samples were collected upstream and downstream of the paper mill's wastewater treatment plant discharge as well as within the mill processes. Samples were analyzed for indicator organisms (coliforms, E. coli, and enterococci) and microbial source tracking (MST) targets. Although indicator concentrations were typically below detection limits in the mill process water, indicators regrew in the activated sludge wastewater treatment process such that fecal coliforms and E. coli were detected in all wastewater treatment plant effluent samples. Although the paper mill effluent periodically appears to affect the E. coli levels at the downstream beach, MST results demonstrate that E. coli from the mill is not of human fecal origin, and therefore not likely a cause for health concerns. [ABSTRACT FROM AUTHOR]

Microbial xylanase has wide application in bioenergy, animal feed, environmental protection, the pulp and paper industry, and agricultural development. In this study, three xylanases from the microbiota of T. fuciformis with its companion strains were identified by metagenomics sequencing. The three enzymes were subjected to cloning and expression in E. coli or P. pastoris, purification, and characterization for their properties. The results showed that AsXyn1, from Annulohypoxylon stygium, among the three enzymes possessed high thermostability at 40 °C and broad pH tolerance in the range of 2.0–10.0, exhibiting its application potential. Furthermore, it was found that post-translational modification (such as glycosylation) of AsXyn1 enzyme modulated its activity, kinetic parameters, and thermostability. These results and findings provided a hint for enzyme modification and design in future. [ABSTRACT FROM AUTHOR]

In this work, paper was rendered antimicrobial via applying antimicrobialmodified starch as a coating material onto the paper's surface. The antimicrobial starch was prepared by covalently bonding guanidine polymers using a coupling reaction. Two different coating layers were applied onto the paper's surface. The first coating layer contained clay mixed with a latex binder (clay 100 g/latex 20 g). The antimicrobial starches, which possessed different grafting ratios of the antimicrobial agent (30 wt.% and 50 wt.%), were applied as the second coating layer on the paper. The results showed that the coating thickness was approximately constant at 4 µm. In the presence of 0.5 to 1.0 wt.% antimicrobial starch on cellulose fibers, the growth inhibition of bacteria was almost 100%. Additionally, the resulting coated paper exhibited high antimicrobial activities against E. coli. Furthermore, the results showed that the coated papers prevented fungal growth. [ABSTRACT FROM AUTHOR]

A simple and rapid filter paper technique is described for processing samples from glucose uptake studies with whole cells of gram-positive or gram-negative bacteria that transport glucose via group translocation. The procedure yields results equivalent to those obtained with a conventional membrane filtration method and requires no special filtration equipment or source of vacuum.

To utilize autoradiographic colony-sorting techniques (C. R. H. Raetz, Proc. Natl. Acad. Sci. U.S.A. 72:2274-2278, 1975) for the isolation of mutants with unstable enzymes, we report a new desiccation-induced lysis method, compatible with low temperatures. Furthermore, a general, two-step protocol is presented for clonal detection of hydrolytic reactions. The advantages of these critical modifications are demonstrated with the membrane enzymes glycerol 3-phosphate acyltransferase and cytidine 5'-diphosphate-diglyceride hydrolase.

We have developed a novel, high-throughput scintillation proximity assay to measure the membrane-associated steps (stages 2 and 3) of peptidoglycan synthesis in Escherichia coli. At least five enzymes are involved in these two stages, all of which are thought to be essential for the survival of the cell. The individual enzymes are difficult to assay since the substrates are lipidic and difficult to isolate in large quantities and analysis is done by paper chromatography. We have assayed all five enzymes in a single mixture by monitoring synthesis of cross-linked peptidoglycan, which is the final product of the pathway. E. coli membranes are incubated with the two sugar precursors, UDP-N-acetyl muramylpentapeptide and UDP-[(3)H]-N-acetylglucosamine. The radiolabel is incorporated into peptidoglycan, which is captured using wheat germ agglutinin-coated scintillation proximity assay beads. The assay monitors the activity of the translocase (MraY), the transferase (MurG), the lipid pyrophosphorylase, and the transglycosylase and transpeptidase activities of the penicillin-binding proteins. Vancomyin, tunicamycin, nisin, moenomycin, bacitracin, and penicillin inhibit the assay, and these inhibitors have been used to validate the assay. The search for new antimicrobial agents that act via the late stages of peptidoglycan biosynthesis can now be performed in high throughput in a microtiter plate.

Recently the genes encoding the human and Escherichia coli GDP-mannose dehydratase and GDP-fucose synthetase (GFS) protein have been cloned and it has been shown that these two proteins alone are sufficient to convert GDP mannose to GDP fucose in vitro. GDP-fucose synthetase from E. coli is a novel dual function enzyme in that it catalyzes epimerizations and a reduction reaction at the same active site. This aspect separates fucose biosynthesis from that of other deoxy and dideoxy sugars in which the epimerase and reductase activities are present on separate enzymes encoded by separate genes. By NMR spectroscopy we have shown that GFS catalyzes the stereospecific hydride transfer of the ProS hydrogen from NADPH to carbon 4 of the mannose sugar. This is consistent with the stereospecificity observed for other members of the short chain dehydrogenase reductase family of enzymes of which GFS is a member. Additionally the enzyme is able to catalyze the epimerization reaction in the absence of NADP or NADPH. The kinetic mechanism of GFS as determined by product inhibition and fluorescence binding studies is consistent with a random mechanism. The dissociation constants determined from fluorescence studies indicate that the enzyme displays a 40-fold stronger affinity for the substrate NADPH as compared with the product NADP and utilizes NADPH preferentially as compared with NADH. This study on GFS, a unique member of the short chain dehydrogenase reductase family, coupled with that of its recently published crystal structure should aid in the development of antimicrobial or anti-inflammatory compounds that act by blocking selectin-mediated cell adhesion.

This study investigates the ability of cellulose filter paper coated with silver nanoparticles to removeEscherichia colifrom drinking water. The cellulose filter paper was coated with silver nanoparticles by a chemical reduction method using two different ratios of sodium borohydride and silver nitrate. In consideration of drinking-water quality standards and non-carcinogenic health risks, the optimum sodium borohydride:silver nitrate ratio for coating the cellulose filter paper was determined by comparing the silver in the effluent afterE. coliremoval. For both ratios, 100%E. coliremoval was realised. In terms of the silver in the effluent, only the first two lowest concentrations for both ratios of sodium borohydride and silver nitrate were compliant with the drinking-water quality standards, demonstrating hazard quotients (HQs) between 0.084 and 0.484. On the basis of the highest level ofE. coliremoval with the lowest HQ value, the optimum sodium borohydride:silver nitrate ratio for coating the cellulose filter paper as an antibacterial water filter was 2:1 molar ratio (0.002 M:0.001 M). Silver nanoparticle-coated cellulose filter paper was found to be an inexpensive and easy-to-use emergency antibacterial water filter to generate clean drinking water. [ABSTRACT FROM PUBLISHER]

We report the results of an interdisciplinary collaboration formed to assess the sterilizing capabilities of the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP). This newly-invented source of glow discharge plasma (the fourth state of matter) is capable of operating at atmospheric pressure in air and other gases, and of providing antimicrobial active species to surfaces and workpieces at room temperature as judged by viable plate counts. OAUGDP exposures have reduced log numbers of bacteria, Staphylococcus aureus and Escherichia coli, and endospores from Bacillus stearothermophilus and Bacillus subtilis on seeded solid surfaces, fabrics, filter paper, and powdered culture media at room temperature. Initial experimental data showed a two-log10 CFU reduction of bacteria when 2 x 10(2) cells were seeded on filter paper. Results showed > or = 3 log10 CFU reduction when polypropylene samples seeded with E. coli (5 x 10(4)) were exposed, while a 30 s exposure time was required for similar killing with S. aureus-seeded polypropylene samples. The exposure times required to effect > or = 6 log10 CFU reduction of E. coli and S. aureus on polypropylene samples were no longer than 30 s. Experiments with seeded samples in sealed commercial sterilization bags showed little or no differences in exposure times compared to unwrapped samples. Plasma exposure times of less than 5 min generated > or = 5 log10 CFU reduction of commercially prepared Bacillus subtilis spores (1 x 10(5)); 7 min OAUGDP exposures were required to generate a > or = 3 log10 CFU reduction for Bacillus stearothermophilus spores. For all microorganisms tested, a biphasic curve was generated when the number of survivors vs time was plotted in dose-response cures. Several proposed mechanisms of killing at room temperature by the OAUGDP are discussed.

Escherichia coli KO11 was previously constructed to produce ethanol from acid hydrolysates of hemicellulose (pentoses and hexoses) by the chromosomal integration of Zymomonas mobilis genes encoding pyruvate decarboxylase (pdc) and alcohol dehydrogenase (adhB). Klebsiella oxytoca P2 was constructed in an analogous fashion for the simultaneous saccharification and fermentation of cellulose and contains PTS enzymes for cellobiose. In this study, KO11 was further engineered for the fermentation of cellulose by adding the K. oxytoca casAB genes encoding Enzyme IIcellobiose and phospho-beta-glucosidase. Although the two K. oxytoca genes were well expressed in cloning hosts such as DH5 alpha, both were expressed poorly in E. coli KO11, a derivative of E. coli B. Spontaneous mutants which exhibited more than 15-fold-higher specific activities for cellobiose metabolism were isolated. The mutations of these mutants resided in the plasmid rather than the host. Three mutants were characterized by sequence analysis. All contained similar internal deletions which eliminated the casAB promoter and operator regions and placed the lacZ Shine-Dalgarno region immediately upstream from the casA Shine-Dalgarno region. KO11 harboring mutant plasmids (pLOI1908, pLOI1909, or pLOI1910) rapidly fermented cellobiose to ethanol, and the yield was more than 90% of the theoretical yield. Two of these strains were used with commercial cellulase to ferment mixed-waste office paper to ethanol.

Global food systems can benefit significantly from continuous monitoring of microbial food safety, a task for which tedious operations, destructive sampling, and the inability to monitor multiple pathogens remain challenging. This study reports significant improvements to a paper chromogenic array sensor - machine learning (PCA-ML) methodology sensing concentrations of volatile organic compounds (VOCs) emitted on a species-specific basis by pathogens by streamlining dye selection, sensor fabrication, database construction, and machine learning and validation. This approach enables noncontact, time-dependent, simultaneous monitoring of multiple pathogens (Listeria monocytogenes , Salmonella , and E. coli O157:H7) at levels as low as 1 log CFU/g with over 90% accuracy. The report provides theoretical and practical frameworks demonstrating that chromogenic response, including limits of detection, depends on time integrals of VOC concentrations. The paper also discusses the potential for implementing PCA-ML in the food supply chain for different food matrices and pathogens, with species- and strain-specific identification. [ABSTRACT FROM AUTHOR]

The rapid and specific point-of-care (POC) analysis of virulent pathogenic strains plays a key role in ensuring food quality and safety. In this work, a paper-based fluorescent phage biosensor was developed for the detection of the virulent E. coli O157:H7 strain (as the mode of virulent pathogens) in food samples. Firstly, phages that can specifically combine with E. coli O157:H7 (E. coli) were stained with SYTO-13 dye to prepare a novel fluorescent probe (phage@SYTO). Simultaneously, a micro-porous membrane filter with a pore size of 0.45 μm was employed as a paper chip so as to retain the E. coli-phage@SYTO complex (>1.2 μm) on its surface. The phage@SYTO (200 nm in size) was able to pass through the pores of the chip, and the complex could be retained on the paper chip using the free phage@SYTO probes. The E. coli-phage@SYTO could emit a visual fluorescent signal (excited at 365 nm; emitted at 520 nm) onto the chip, which could be detected by a smartphone to reflect the concentration of E. coli. Under optimized conditions, the detection limit was as low as 50 CFU/mL (S/N = 3) and exhibited a wide linear range from 102 to 106 CFU/mL. The sensor has potential application value for the quick and specific POCT detection of virulent E. coli in foods. [ABSTRACT FROM AUTHOR]

Insufficiently treated wastes contained within onsite sanitation systems (OSS) commonly used by disadvantaged and developing communities contribute to public and environmental health concerns, calling for practical alternative solutions. At the basic level, an improved understanding of the evolution of chemical and physical constituents under different waste introduction methods and for short-term and long-term operation is needed. While receiving non-dilute waste under mixed, unmixed, toilet paper exclusion, and urine diversion (UD) regimes, self-flushing OSS simulated using anaerobic digesters (ADs) were compared during three operational stages: (1) 0–1 month service for unsheltered encampments; (2) 1–3 month disaster relief scenario; and (3) ≥ 3 months representing refugee camps and long-term household use. Although stratification was found to promote suitable conditions for short-term use of self-flushing toilets, mixing increased beneficial biodegradation of organic constituents. Urine-containing ADs demonstrated a shift from sulfide to ammonia odor accompanied by high pH (> 8) after ~ 240 d. E. coli reduction following elevated nitrogen and dissolved solids levels pointed to decreased pathogen survival in ADs with urine. The benefits of bacterial disinfection, reduction of sulfurous odors, and heightened organics degradation in mixed, urine-containing ADs suggest this format as more desirable for prolonged use of self-flushing OSS over unmixed or urine-diverting formats. [ABSTRACT FROM AUTHOR]

Starvation of a mid-log-phase culture of Escherichia coli B/r for nitrogen, phosphate, or carbon resulted in methylation of a membrane-associated protein of about 43,000 daltons (P-43) in the presence of chloramphenicol and [methyl-3H]methionine. The in vivo methylation reaction occurred with a doubling time of 2 to 5 min and was followed by a slower demethylation process. Addition of the missing nutrient to a starving culture immediately prevented further methylation of P-43. P-43 methylation is not related to the methylated chemotaxis proteins because P-43 is methylated in response to a different spectrum of nutrients and because P-43 is methylated on lysine residues. The characteristics of P-43 are similar to those of a methylated protein previously described in Bacillus subtilis and B. licheniformis (R. W. Bernlohr, A. L. Saha, C. C. Young, B. R. Toth, and K. J. Golden, J. Bacteriol. 170:4113-4118, 1988; K. J. Golden and R. W. Bernlohr, Mol. Gen. Genet. 220:1-7, 1989) and are consistent with the proposal that methylation of this protein functions in nutrient sensing.