Hydraulic resistance of biofilms Dreszer, C.; Vrouwenvelder, J.S.; Paulitsch-Fuchs, A.H. ...
Journal of membrane science,
02/2013, Letnik:
429
Journal Article
Recenzirano
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 100Lm−2h−1) and constant cross flow (0.1ms−1). As a nutrient source, acetate was added (1.0mgL−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 20Lm−2h−1 flux with a nutrient dosage of 1mgL−1 acetate C, the resistance after 4 days reached a value of 6×1012m−1. At 100Lm−2h−1 flux under the same conditions, the resistance was 5×1013m−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 cellscm−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 100Lm−2h−1 with nutrient supply caused higher cell numbers, more biomass, and higher biofilm resistance than a flux of 20Lm−2h−1. However, the biofilm thickness after 4 days at a flux of 100Lm−2h−1 (97μm) was in the same order of magnitude as the thickness of a biofilm at a flux of 20Lm−2h−1 (114μm). 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 (6×1012m−1) was high compared to the intrinsic resistance of the employed MF membrane (5×1011m−1). However, in nanofiltration (intrinsic membrane resistance ca. 2×1013m−1) and reverse osmosis membranes (intrinsic resistance ca. 9×1013m−1), the biofilm will not contribute significantly to the overall resistance.
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► The resistance of the biofilm reaches values up to 50 × 1012 m−1. ► Effect of growing biofilms dominated that of bacterial filter cakes at same density. ► The resistance was not caused by the biofilm cells but by the EPS matrix. ► No correlation between biofilm thickness and resistance could be found. ► The flux impacted the trans membrane biofilm resistance.
•Scaling of CaCO3 in undersaturated drinking water can be initiated by microbial activity.•CaCO3 formation is overlooked in biofilm formation processes.•Bacteria can use different mechanisms to ...mediate CaCO3 precipitation.•Bacteria can play an active role in the microbial CaCO3 precipitation process.•Different CaCO3 polymorphs can result from the microbial processes.
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.
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The drinking water scarcity is posing a threat to mankind, hence better water quality management methods are required. Magnetic water treatment, which has been reported to improve aesthetic water ...quality and reduce scaling problems, can be an important addition to the traditional disinfectant dependent treatment. Despite the extensive market application opportunities, the effect of magnetic fields on (microbial) drinking water communities and subsequently the biostability is still largely unexplored, although the first patent was registered already 1945.
Here flow cytometry was applied to assess the effect of weak magnetic fields (≤10 G) with strong gradients (≈800 G/m) on drinking water microbial communities. Drinking water was collected from the tap and placed inside the magnetic field (treated) and 5 m away from the magnet to avoid any background interferences (control) using both a static set-up and a shaking set-up. Samples were collected during a seven-day period for flow cytometry examination. Additionally, the effects of magnetic fields on the growth of Pseudomonas aeruginosa in autoclaved tap water were examined. Based on the fluorescent intensity of the stained nucleic acid content, the microbial cells were grouped into low nucleic acid content (LNA) and high nucleic acid content (HNA). Our results show that the LNA was dominant under nutrient limited condition while the HNA dominates when nutrient is more available. Such behavior of LNA and HNA matches well with the long discussed r/K selection model where r-strategists adapted to eutrophic conditions and K-strategists adapted to oligotrophic conditions. The applied magnetic fields selectively promote the growth of LNA under nutrient rich environment, which indicates a beneficial effect on biostability enhancement. Inhibition on an HNA representative Pseudomonas aeruginosa has also been observed. Based on our laboratory observations, we conclude that magnetic field treatment can be a sustainable method for microbial community management with great potential.
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•Growth kinetics of LNA/HNA in stagnated drinking water observed.•Experimental data supporting the application of r/K-strategy to microbial communities.•Provided theoretical framework on drinking water biostability measurement.•Weak magnetic field can selective promote LNA growth under certain condition.•Magnetic water treatment has potential for drinking water biostability management.
Extended spectrum beta lactamases producing Enterobacteriaceae are a major player in the antibiotic resistance challenge. In general, the situation regarding antibiotic resistance in Austria is very ...good compared to many other countries. Perhaps this is why there is a lack of data on the distribution of ESBL genes in the clinical setting. The aim of this study was to collect data on ESBL genes from a larger sample of human non-invasive clinical isolates from one region in Austria. In total, 468 isolates from different sample materials isolated at the Medical University of Graz from 2017 were examined. The most frequent organisms were
and
. Among the enzymes produced, CTX-M-15 was clearly dominant, exotic ESBLs were only represented by three
isolates harboring genes for VEB-6 and one
for CTX-M-2, respectively. Compared to other countries, the results are in line with the expectations. The data help to better classify the many studies from the non-clinical field in Austria and to shift the focus slightly away from the exotic results and sample sites.
Polycrystalline sub-micron-sized GdAl3(BO3)4 phosphors co-doped with Eu3+, Tb3+, Dy3+ and Tm3+ have been prepared by combustion synthesis with urea. The phosphors have been characterised by X-ray ...diffraction, scanning electron microscopy, excitation and emission spectroscopy. The chromaticity co-ordinates and the colour temperatures of the fluorescence of the materials presented have been calculated and analysed with Commission Internationale l'Eclairage (CIE) programs and diagrams. Depending on the excitation wavelength, different colour temperatures of the light emitted can be achieved. Due to its polyspectral nature, the emitted light reveals a high colour rendering index.
Periprosthetic infections are an eminent factor in patient care and also having significant economic implications. The number of biofilm-infection related replacement surgeries is increasing and will ...continue to do so in the following decades. To reduce both the health burden of the patients and the costs to the healthcare sector, new solutions for implant materials resistant to such infections are necessary. This study researches different surface modifications of cobalt-chromium-molybdenum (CoCrMo) based implant materials and their influence on the development of biofilms. Three smooth surfaces (CoCrMo, CoCrMo TiN, and CoCrMo polished) and three rough surfaces (CoCrMo porous coated, CoCrMo cpTi, and CoCrMo TCP) are compared. The most common infectious agents in periprosthetic infections are
and Coagulase-negative
(e.g.,
), therefore strains of these two species have been chosen as model organisms. Biofilms were grown on material disks for 48 h and cell number, polysaccharide content, and protein contend of the biofilms were measured. Additionally, regulation of genes involved in early biofilm development (
,
,
,
,
,
;
,
) was detected using RT-q-PCR. All results were compared to the base alloy without modifications. The results show a correlation between the surface roughness and the protein and polysaccharide content of biofilm structures and also the gene expression of the biofilms grown on the different surface modifications. This is supported by the significantly different protein and polysaccharide contents of the biofilms associated with rough and smooth surface types. Additionally, early phase biofilm genes (particularly
,
, and
) are statistically significantly downregulated compared to the control at 48 h on rough surfaces. CoCrMo TiN and polished CoCrMo were the two smooth surface modifications which performed best on the basis of low biofilm content.
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 authors wish to make the following corrections to this paper 1: In all instances mentioning “2 kG·m−1”, these gradients should be replaced by “770 G·m−1 (WCM 62081992) and 740 G·m−1 (WCM ...62083545)”: Abstract, page 1, line 4; Chapter 1 ...
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
(
,
,
,
,
,
) and
(
,
).
In this study, an alternative parameter for quantifying the signals of fluorescently labelled bacteria (e.g. propidium iodide, Cyanine 3, etc.) in microscopic images was investigated. Three common ...parameters (mean grey value (MGV), mean grey value which is corrected for the background (MGVcwB) and the signal to background ratio (SBR) per bacterial cell) are used as reference parameters. As an alternative, the coefficient of variation (CV) is defined as the ratio of the logarithm of the standard deviation and the logarithm of the mean grey value of a bacterial cell in a microscopic image. The actual fluorescence value was safeguarded by measuring commercially available fluorescence latex microspheres at regular time intervals within our study. The precision and the correlation of the respective values of MGV, MGVcwB, SBR and CV taken from identical images were measured and subsequently normalized in order to enhance the inter-parameter comparability. The average precision of CV was the highest (89% ± 14) with decreasing numbers for MGVcwB, SBR, and MGV (78% ± 25, 71% ± 32, and, 52% ± 22, respectively). Changes in operational parameters, e.g., microscope settings, protocol steps, etc., yielded good results for the CV but less precise results for MGV, MGVcwB, and SBR in the analyses of identical images.
In conclusion, using the alternative parameter CV, changes in the composition of microbial ecosystems may thus be investigated at the highest precision level.
•Development and validation of an alternative parameter, the coefficient of variation, for the quantification of fluorescence signals emitted by bacterial cells labelled with propidium iodide or Cy3.•Comparing precision values of mean grey value, mean grey value corrected with the background, signal to background ratio and the alternative parameter.•Assessing the performance characteristics of the alternative parameter at different ultraviolet exposure times.•Assessing the performance characteristics of the alternative parameter using reaction and washing buffers of different compositions.
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