Wetting properties of biofilm-coated surfaces produced at controlled shear flow conditions

2020 ◽  
Author(s):  
Federica Recupido ◽  
Maria Petala ◽  
Margaritis Kostoglou ◽  
Sergio Caserta ◽  
Stefano Guido ◽  
...  
Keyword(s):  
Shear Flow ◽  
Nutrient Concentration ◽  
Growth Conditions ◽  
Centrifugal Forces ◽  
Flow Conditions ◽  
Initial Shape ◽  
Biofilm Growth ◽  
Droplet Shape ◽  
Wetting Properties ◽  
Custom Made

<p>Biofilms prevention and removal are crucial in many industrial and medical applications. Their complex and cohesive structure provides resistance to cleaning even to strong disinfectants. A key factor for their behavior is the wetting properties of their surfaces.</p> <p>The main goal of this work is to study the wetting properties of biofilms produced by bacteria <em>Pseudomonas fluorescens</em>. Biofilms are obtained on glass coupons under well controlled flow conditions, using custom-made flow cell devices. Different nutrient concentration and shear flow conditions are investigated.</p> <p>Biofilm wetting properties are examined under imposed external body forces (forced wetting) through a specialized device, named Kerberos®. Kerberos® is capable of subjecting sessile droplets to varying tilting angles and centrifugal forces while monitoring the variation of the droplet shape in X, Y and Z-directions through three Wi-Fi cameras. Wetting experiments are carried out using water-based solution (dye solution) droplets on biofilm-coated glass coupons. In this work, spreading/sliding behaviour of droplets are investigated only on horizontal substrates (no tilting) under the action of centrifugal forces. Apart from wetting properties, biofilm growth kinetics and surface morphology at different nutrient and shear flow conditions are also assessed.</p> <p>Results show that, according to the different growth conditions, biofilms present different wetting properties. At lower nutrient concentration and shear flow conditions, spreading and sliding behaviour are similar to that observed in glass coupons in the absence of biofilm. At higher nutrient and shear flow conditions, spontaneous wicking of the biofilm occurs the moment of droplet deposition on the biofilm leading to irregular and jagged shapes of droplets, while on the contrary water droplets look like smooth spherical sections on pure glass. The spontaneous wicking affects the droplet initial shape and so the wetting behaviour during the subsequent rotation tests. In each examined condition, biofilms show hydrophilic properties.</p> <p> </p>

Pseudomonas Fluorescens biofilm in rotating annular bioreactor: formation kinetics and wetting properties

2020 ◽  
Author(s):  
Michela Castigliano ◽  
Maria Petala ◽  
Margaritis Kostoglou ◽  
Stefano Guido ◽  
Sergio Caserta ◽  
...  
Keyword(s):  
Pseudomonas Fluorescens ◽  
Growth Kinetics ◽  
Waste Water Treatment ◽  
Tangential Force ◽  
Growth Conditions ◽  
Bacterial Biofilm ◽  
Support Surface ◽  
Droplet Shape ◽  
Wetting Properties

<p>Biofilms are bacterial communities embedded in an extracellular matrix, able to adhere to surfaces. A deeper knowledge of the biofilm as a whole will aid the development of efficient methods to control deleterious biofilms (clinical biofilms, biofouling) or to enhance beneficial ones (waste-water treatment, bio-filtration). P. fluorescens has been widely studied, this strain produces bioactive secondary metabolites, and forms biofilms[1]. Several experimental set-ups have been widely used for in vitro biofilm cultivation of P. fluorescens, even if a deep characterization among different culture conditions is still lacking in the literature. This work, based on previous studies[2], is focused on the investigation of growth conditions on biofilm structure and properties. Growth kinetics of P. fluorescens biofilms was characterized in vitro under stagnant and flow-controlled conditions, using a rotating annular bioreactor. Two different supports in borosilicate glass and polycarbonate have been used. Bacterial growth kinetics has been measured through bio-turbidity analysis and TOC/DOC quantification. Biofilm morphology has been quantified through optical microscopy and image analysis by measuring the fraction of support surface covered by biofilm. The wetting properties of the biofilm layers have been investigated by using an innovative device, named Kerberos®, able to control centrifugal and gravitational forces acting on a single droplet placed on a surface[3]. The evolution of the droplet shape and position was measured as function of the imposed stress, to quantify wetting of different biofilm coated samples, following already assessed methodologies[4]. Different chemo-physical environments, investigated by changing growth medium, physical support, and imposed flow stress, induced different growth kinetics, biofilm morphology, and wetting properties. Accurate experimental measurements allowed us to estimate in a quantitative way the influence of investigated parameters on specific morphologic measurements.</p> <div><br /> <div> <p>[1] Brittan S. Scales and others, ‘Microbiology, Genomics, and Clinical Significance of the Pseudomonas Fluorescens Species Complex, an Unappreciated Colonizer of Humans’, Clinical Microbiology Reviews, 27.4 (2014), 927–48 <https://doi.org/10.1128/CMR.00044-14>.</p> </div> <div> <p>[2] Federica Recupido and others, ‘The Role of Flow in Bacterial Biofilm Morphology and Wetting Properties’, Colloids and Surfaces B: Biointerfaces, 2020 <https://doi.org/10.1016/j.colsurfb.2020.111047>.</p> </div> <div> <p>[3] Sotiris P. Evgenidis and others, ‘Kerberos: A Three Camera Headed Centrifugal/Tilting Device for Studying Wetting/Dewetting under the Influence of Controlled Body Forces’, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017 <https://doi.org/10.1016/j.colsurfa.2016.07.079>.</p> </div> <div> <p>[4] Inmaculada Ríos-López and others, ‘Effect of Initial Droplet Shape on the Tangential Force Required for Spreading and Sliding along a Solid Surface’, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2018 <https://doi.org/10.1016/j.colsurfa.2018.04.004>.</p> </div> </div>

scholarly journals Cell Surface Expression of Nrg1 Protein in Candida auris

2021 ◽  
Vol 7 (4) ◽  
pp. 262
Author(s):  
Anuja Paudyal ◽  
Govindsamy Vediyappan
Keyword(s):  
Cell Surface ◽  
Growth Conditions ◽  
Zinc Ion ◽  
Surface Proteins ◽  
Cell Surface Expression ◽  
Unexpected Finding ◽  
Candida Auris ◽  
Cell Surface Proteins ◽  
Biofilm Growth

Candida auris is an emerging antifungal resistant human fungal pathogen increasingly reported in healthcare facilities. It persists in hospital environments, and on skin surfaces, and can form biofilms readily. Here, we investigated the cell surface proteins from C. auris biofilms grown in a synthetic sweat medium mimicking human skin conditions. Cell surface proteins from both biofilm and planktonic control cells were extracted with a buffer containing β-mercaptoethanol and resolved by 2-D gel electrophoresis. Some of the differentially expressed proteins were excised and identified by mass spectrometry. C. albicans orthologs Spe3p, Tdh3p, Sod2p, Ywp1p, and Mdh1p were overexpressed in biofilm cells when compared to the planktonic cells of C. auris. Interestingly, several proteins with zinc ion binding activity were detected. Nrg1p is a zinc-binding transcription factor that negatively regulates hyphal growth in C. albicans. C. auris does not produce true hypha under standard in vitro growth conditions, and the role of Nrg1p in C. auris is currently unknown. Western blot analyses of cell surface and cytosolic proteins of C. auris against anti-CalNrg1 antibody revealed the Nrg1p in both locations. Cell surface localization of Nrg1p in C. auris, an unexpected finding, was further confirmed by immunofluorescence microscopy. Nrg1p expression is uniform across all four clades of C. auris and is dependent on growth conditions. Taken together, the data indicate that C. auris produces several unique proteins during its biofilm growth, which may assist in the skin-colonizing lifestyle of the fungus during its pathogenesis.

Dynamics of a non-spherical microcapsule with incompressible interface in shear flow

2011 ◽  
Vol 678 ◽  
pp. 221-247 ◽  
Author(s):  
P. M. VLAHOVSKA ◽  
Y.-N. YOUNG ◽  
G. DANKER ◽  
C. MISBAH
Keyword(s):  
Shear Rate ◽  
Shear Flow ◽  
Viscosity Ratio ◽  
Perturbation Expansion ◽  
Shear Plane ◽  
Creeping Flow ◽  
Regular Perturbation ◽  
Cell Dynamics ◽  
Initial Shape ◽  
Flow Equations

We study the motion and deformation of a liquid capsule enclosed by a surface-incompressible membrane as a model of red blood cell dynamics in shear flow. Considering a slightly ellipsoidal initial shape, an analytical solution to the creeping-flow equations is obtained as a regular perturbation expansion in the excess area. The analysis takes into account the membrane fluidity, area-incompressibility and resistance to bending. The theory captures the observed transition from tumbling to swinging as the shear rate increases and clarifies the effect of capsule deformability. Near the transition, intermittent behaviour (swinging periodically interrupted by a tumble) is found only if the capsule deforms in the shear plane and does not undergo stretching or compression along the vorticity direction; the intermittency disappears if deformation along the vorticity direction occurs, i.e. if the capsule ‘breathes’. We report the phase diagram of capsule motions as a function of viscosity ratio, non-sphericity and dimensionless shear rate.

Stressed Response of Submerged Elodea nattalii under Eutrophication Growth Conditions

2012 ◽  
Vol 610-613 ◽  
pp. 229-234
Author(s):  
Han Feng Xiong ◽  
Qi Ling Tan
Keyword(s):  
Superoxide Dismutase ◽  
Enzyme Activity ◽  
Aquatic Plants ◽  
Nutrient Concentration ◽  
Growth Conditions ◽  
Antioxidant Enzyme Activity ◽  
Metabolic Responses ◽  
Concentration Increase ◽  
Time Period ◽  
Mda Content

Eutrophication in water bodies affects the growth of aquatic plants. In this study, we conducted static experiments to better understand the metabolic responses of Elodea nattalii under eutrophication conditions. The nitrogen (N) and phosphorous (P) levels in tissue, malondiadehyde (MDA), and activities of three antioxidases (peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT)) of Elodea nattalii cultured at different nutrient levels (oligotropher, mesotropher, eutropher, and hypertrophics) were investigated. The results showed that with nutrient concentration increase, N and P contents of Elodea nattalii increased. The MDA content improved with nutrient increase. the POD activity initially increased and later decreased. CAT and SOD activities decreased during the experimental time period. These finding suggested that changes in stem the increase of antioxidant enzyme activity can be served as the indicators of the response of Elodea nattalii to eutrophication conditions.

scholarly journals Numerical simulation of single gas bubbles under shear flow conditions

PAMM ◽  
2009 ◽  
Vol 9 (1) ◽  
pp. 471-472
Author(s):  
Peter Lakshmanan ◽  
Peter Ehrhard
Keyword(s):  
Numerical Simulation ◽  
Shear Flow ◽  
Gas Bubbles ◽  
Flow Conditions

Existence Limits for Straight and Curved Interfaces Exposed to Temperature Gradients

2003 ◽  
Author(s):  
J. M. Floryan ◽  
M. El-Gammal
Keyword(s):  
Thermal Management ◽  
Extreme Values ◽  
Flow Conditions ◽  
Thermocapillary Effect ◽  
Initial Shape ◽  
Interface Deformation ◽  
Strongly Coupled ◽  
Flow Parameters ◽  
Flow Response ◽  
External Heating

Distortion of capillary interfaces exposed to external heating is analyzed. This problem is of interest in material processing under zero gravity conditions and in thermal management of spacecrafts. The analysis is focused on a model problem where thermocapillary effect is the dominant driving force. Flow response to an external heating consists of convection in the liquid and interface deformation, with both effects being strongly coupled. Detailed results are presented in the case of cavity with a free upper surface. It is demonstrated that large interface deformation and rupture represent the dominant response of such dynamical system if the interface is sufficiently long. Flow conditions corresponding to the limits points have been identified. Limit points identify extreme values of flow parameters that guarantee the existence of steady continuous interface. It is shown that rupture can be delayed by changing the mass of the fluid, i.e., changing the initial shape of the interface.

Role of Von Willebrand Factor Triplet Bands in Glycoprotein Ib-Dependent Platelet Adhesion Under Flow Conditions

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3356-3356
Author(s):  
Bruce A. Schwartz ◽  
Christoph Kannicht ◽  
Birte Fuchs ◽  
Mario Kröning ◽  
Barbera Solecka
Keyword(s):  
Shear Flow ◽  
Platelet Adhesion ◽  
Collagen Type ◽  
Peptide Sequence ◽  
High Shear ◽  
Collagen Type Iii ◽  
Flow Conditions ◽  
Triplet Structure ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Abstract 3356 Objective: Multimeric glycoprotein von Willebrand factor (VWF) exhibits a unique triplet structure of individual oligomers, resulting from ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motifs 13) cleavage. The faster and slower migrating triplet bands of a given VWF multimer respectively have one shorter or longer N-terminal peptide sequence. Within this peptide sequence, the A1 domain regulates interaction of VWF with platelet glycoprotein (GP)Ib. Distribution of VWF triplet bands is significantly altered in some types of VWD, however, the impact of triplet structure on VWF function has not been investigated so far. Methods: Platelet-adhesive properties of two VWF preparations with similar multimeric distribution but different triplet composition obtained by size exclusion in addition to heparin affinity chromatography were investigated for differential functional activities. Preparation A was enriched in intermediate triplet bands, while preparation B predominantly contained larger triplet bands. Collagen- and GPIb-binding was determined by surface plasmon resonance (SPR). Platelet adhesion under flow was determined using flow-chamber models. Results: Binding studies revealed that preparation A displayed a reduced affinity for recombinant GPIb, but an unchanged affinity for collagen type III, when compared to preparation B. Under high-shear flow conditions, preparation A was less active in recruiting platelets to collagen type III. Furthermore, when added to blood from patients with von Willebrand disease (VWD), defective thrombus formation was less restored. Conclusion: Thus, VWF forms lacking larger size triplet bands appear to have a decreased potential to recruit platelets to collagen-bound VWF under arterial flow conditions. By implication, changes in triplet band distribution observed in patients with VWD may result in altered platelet adhesion at high-shear flow. Disclosures: Schwartz: Octapharma: Employment. Kannicht:Octapharma: Employment. Fuchs:octapharma: Employment. Kröning:octapharma: Employment. Solecka:Octapharma: Employment.

Study on the solid-state shear pulverization in shear flow conditions

Polimery ◽  
2005 ◽  
Vol 50 (10) ◽  
pp. 755-761 ◽  
Author(s):  
TOMASZ RUSIECKI ◽  
RYSZARD STELLER
Keyword(s):  
Solid State ◽  
Shear Flow ◽  
Flow Conditions

Roll cells and disclinations in sheared nematic polymers

2001 ◽  
Vol 449 ◽  
pp. 179-200 ◽  
Author(s):  
J. J. FENG ◽  
J. TAO ◽  
L. G. LEAL
Keyword(s):  
Shear Rate ◽  
Shear Flow ◽  
Simple Shear ◽  
Flow Direction ◽  
Flow Regimes ◽  
Flow Conditions ◽  
Break Up ◽  
Nematic Polymers ◽  
Defect Nucleation

We use the Leslie–Ericksen theory to simulate the shear flow of tumbling nematic polymers. The objectives are to explore the onset and evolution of the roll-cell instability and to uncover the flow scenario leading to the nucleation of disclinations. With increasing shear rate, four flow regimes are observed: stable simple shear, steady roll cells, oscillating roll cells and irregular patterns with disclinations. In the last regime, roll cells break up into an irregular and uctuating pattern of eddies. The director is swept into the flow direction in formations called ‘ridges’, which under favourable flow conditions split to form pairs of ± 1 disclinations with non-singular cores. The four regimes are generally consistent with experimental observations, but the mechanism for defect nucleation remains to be verified by more detailed measurements.

Sign in / Sign up

Export Citation Format

Share Document