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Drinking water plumbing systems appear to be a unique environment for microorganisms as they contain few nutrients but a high mineral concentration. Interactions between mineral content and bacteria, such as microbial calcium carbonate precipitation (MCP) however, has not yet attracted too much attention in drinking water sector. This study aims to carefully examine MCP behavior of two drinking water bacteria species, which may potentially link scaling and biofouling processes in drinking water distribution systems. Evidence from cell density evolution, chemical parameters, and microscopy suggest that drinking water isolates can mediate CaCO3 precipitation through previously overlooked MCP mechanisms like ammonification or biosorption. The results also illustrate the active control of bacteria on the MCP process, as the calcium starts to concentrate onto cell surfaces only after reaching a certain cell density, even though the cell surfaces are shown to be the ideal location for the CaCO3 nucleation.

An aqueous electrohydrodynamic (EHD) floating liquid bridge is a unique environment for studying the influence of protonic currents (mA cm−2) in strong DC electric fields (kV cm−1) on the behavior of microorganisms. It forms in between two beakers filled with water when high-voltage is applied to these beakers. We recently discovered that exposure to this bridge has a stimulating effect on Escherichia coli.. In this work we show that the survival is due to a natural Faraday cage effect of the cell wall of these microorganisms using a simple 2D model. We further confirm this hypothesis by measuring and simulating the behavior of Bacillus subtilis subtilis, Neochloris oleoabundans, Saccharomyces cerevisiae and THP-1 monocytes. Their behavior matches the predictions of the model: cells without a natural Faraday cage like algae and monocytes are mostly killed and weakened, whereas yeast and Bacillus subtilis subtilis survive. The effect of the natural Faraday cage is twofold: First, it diverts the current from passing through the cell (and thereby killing it); secondly, because it is protonic it maintains the osmotic pressure in the cell wall, thereby mitigating cytolysis which would normally occur due to the low osmotic pressure of the surrounding medium. The method presented provides the basis for selective disinfection of solutions containing different microorganisms., Highlights • Microorganisms survive the exposure to high voltage in an electrohydrodynamic liquid bridge. • A simple 2D model shows a natural Faraday cage effect protecting microorganisms against cytolysis. • The method presented provides a basis for selective disinfection of solutions containing different microorganisms.

One of the most serious complications following joint replacement surgeries are periprosthetic infections (PIs) arising from the adhesion of bacteria to the artificial joint. Various types of titanium–aluminum–vanadium (TiAl6V4) alloy surface modifications (coatings with silver (Ag), titanium nitride (TiN), pure titanium (cpTi), combinations of cpTi and hydroxyapatite (HA), combinations of cpTi and tricalcium phosphate (TCP), and a rough-blasted surface of TiAl6V4) have been investigated to assess their effects on biofilm development. Biofilms were grown, collected, and analyzed after 48 h to measure their protein and glucose content and the cell viability. Biofilm-associated genes were also monitored after 48 h of development. There was a distinct difference in the development of staphylococcal biofilms on the surfaces of the different types of alloy. According to the findings of this study, the base alloy TiAl6V4 and the TiN-coated surface are the most promising materials for biofilm reduction. Rough surfaces are most favorable when it comes to bacterial infections because they allow an easy attachment of pathogenic organisms. Of all rough surfaces tested, rough-blasted TiAl6V4 was the most favorable as an implantation material, all the other rough surfaces showed more distinct signs of inducing the development of biofilms which displayed higher protein and polysaccharide contents. These results are supported by RT-qPCR measurements of biofilm associated genes for Staphylococcus aureus (icaA, icaC, fnbA, fnbB, clfB, atl) and Staphylococcus epidermidis (atle, aap).

Granular activated carbon (GAC) is used in water treatment systems, typically to remove pollutants such as natural organic matter, volatile organic compounds, chlorine, taste, and odor. GAC is also used as a key component of a new technology that combines a fluidized bed reactor with radio frequency electric fields for disinfection. So far, the effects of GAC on bacteria in these fluidized bed reactors are unclear. This paper describes a systematic study of the physico-chemical changes in five microbial media compositions caused by different concentrations (23–350?g/L) of GAC, and the effects of these physico-chemical changes on the metabolic activity and survival of a model microorganism (Escherichia coli YMc10) in a fluidized bed reactor. The chemical adsorption taking place in suspensions with specific GAC changed nutritional, osmotic, and pH conditions in the investigated microbial media (LB, diluted LB, PBS, diluted PBS, and tap water), leading to a decay of the metabolic activity and survival of E. coli. Especially media that are poor in organic and mineral compounds (e.g., PBS) with suspended GAC showed a concentration decay of 3.5?Log CFU/mL E. coli after 6?h. Organic compounds depletion and severe pH variation were enhanced in the presence of higher GAC concentrations. Biotechnol. Bioeng. 2014;111: 2009–2018.

In 2012 Coey proposed a theory on the mechanism of magnetic water treatment based on the gradient of the applied field rather than its absolute strength. We tested this theory by measuring the effect of very weak field magnets (≤ 10 G) containing strong magnetic inhomogeneities (ΔB = 770 G·m−1 (WCM 62081992) and 740 G·m−1 (WCM 62083545)) on tap water samples by the use of electric impedance spectroscopy (EIS) and laser scattering. Our results show an increased formation of nm-sized prenucleation clusters (dynamically ordered liquid like oxyanion polymers or “DOLLOPs”) due to the exposure to the magnetic field and thus are consistent with Coey’s theory which is therefore also applicable to very weak magnetic fields as long as they contain strong gradients.

The formation of aqueous bridges containing phenol and ethylene glycol as well as bisphenol-A, hydrochinone and p-cresol under the application of high voltage DC (“liquid bridges”) is reported. Detailed studies were made for phenol and glycol with concentrations from 0.005 to 0.531 mol L−1. Conductivity as well as substance and mass transfers through these aqueous bridges are discussed and compared with pure water bridges. Previously suggested bidirectional mass transport is confirmed for the substances tested. Anodic oxidation happens more efficiently when phenol or glycol are transported from the cathode to the anode since in this case the formation of a passivation layer or electrode poisoning are retarded by the electrohydrodynamic (EHD) flow. The conductivity in the cathode beaker decreases in all experiments due to electrophoretic transport of naturally dissolved carbonate and bicarbonate to the anode. The observed electrochemical behavior is shortly discussed and compared to known mechanisms.

Biofilms may interfere with membrane performance in at least three ways: (i) increase of the transmembrane pressure drop, (ii) increase of feed channel (feed-concentrate) pressure drop, and (iii) increase of transmembrane passage. Given the relevance of biofouling, it is surprising how few data exist about the hydraulic resistance of biofilms that may affect the transmembrane pressure drop and membrane passage. In this study, biofilms were generated in a lab scale cross flow microfiltration system at two fluxes (20 and 100 L m−2 h−1) and constant cross flow (0.1 m s−1). As a nutrient source, acetate was added (1.0 mg L−1 acetate C) besides a control without nutrient supply. A microfiltration (MF) membrane was chosen because the MF membrane resistance is very low compared to the expected biofilm resistance and, thus, biofilm resistance can be determined accurately. Transmembrane pressure drop was monitored. As biofilm parameters, thickness, total cell number, TOC, and extracellular polymeric substances (EPS) were determined, it was demonstrated that no internal membrane fouling occurred and that the fouling layer actually consisted of a grown biofilm and was not a filter cake of accumulated bacterial cells. At 20 L m−2 h−1 flux with a nutrient dosage of 1 mg L−1 acetate C, the resistance after 4 days reached a value of 6×1012 m−1. At 100 L m−2 h−1 flux under the same conditions, the resistance was 5×1013 m−1. No correlation of biofilm resistance to biofilm thickness was found; Biofilms with similar thickness could have different resistance depending on the applied flux. The cell number in biofilms was between 4×107 and 5×108 cells cm−2. At this number, bacterial cells make up less than a half percent of the overall biofilm volume and therefore did not hamper the water flow through the biofilm significantly. A flux of 100 L m−2 h−1 with nutrient supply caused higher cell numbers, more biomass, and higher biofilm resistance than a flux of 20 L m−2 h−1. However, the biofilm thickness after 4 days at a flux of 100 L m−2 h−1 (97 μm) was in the same order of magnitude as the thickness of a biofilm at a flux of 20 L m−2 h−1 (114 μm). An increase of flux caused an increased biofilm resistance while a decrease of flux caused a decreased resistance. The effect was reversible. It is suggested that the biofilm resistance is mainly attributed to EPS, probably due to the tortuosity (“hair-in-sink-effect”) of the biopolymers to water molecules travelling across the biofilm. The data show clearly that biofilm resistance (6×1012 m−1) was high compared to the intrinsic resistance of the employed MF membrane (5×1011 m−1). However, in nanofiltration (intrinsic membrane resistance ca. 2×1013 m−1) and reverse osmosis membranes (intrinsic resistance ca. 9×1013 m−1), the biofilm will not contribute significantly to the overall resistance.

We report on the infrared emission of aqueous bridges under the application of high dc voltage (‘floating water bridge’) over the range between 400 and 2500 cm−1 (4.0–10.3 µm). Comparison with bulk water of the same temperature reveals an additional broad peak at ∼2200 cm−1 as well as water vapour emission lines. Two complementary explanations are presented for the broad peak: first, a cooperative proton transfer comprising an orientational motion along the direction of conduction is suggested. Second, the electrolysis-less current flow is explained by a proton/defect-proton band mechanism, which is in line with the cooperative proton transfer. The water vapour emissions occur due to collision ionization of space charges with micro- and nano-droplets which are electrosprayed from the liquid/gas interface.

Syntrophobacter fumaroxidans strain MPOBT is the best-studied species of the genus Syntrophobacter. The species is of interest because of its anaerobic syntrophic lifestyle, its in-volvement in the conversion of propionate to acetate, H2 and CO2 during the overall degra-dation of organic matter, and its release of products that serve as substrates for other microor-ganisms. The strain is able to ferment fumarate in pure culture to CO2 and succinate, and is also able to grow as a sulfate reducer with propionate as an electron donor. This is the first complete genome sequence of a member of the genus Syntrophobacter and a member genus in the family Syntrophobacteraceae. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 4,990,251 bp long genome with its 4,098 protein-coding and 81 RNA genes is a part of the Microbial Genome Program (MGP) and the Genomes to Life (GTL) Program project.