Jelmer Sjollema

REAL-TIME ENUMERATION OF ADHERING MICROORGANISMS IN A PARALLEL PLATE FLOW CELL USING AUTOMATED IMAGE-ANALYSIS

Abstract A parallel plate flow cell has been developed allowing real-time enumeration of microorganisms adhering to solid substrata using automated image analysis. A detailed description is given of the flow cell system, microscope illumination facilities and specifichydrodynamic conditions in the flow cell. In addition, a method is presented for the distinction of adhering microorganims into singlets and multicellular aggregates.

A Comparison of Thermodynamic Approaches To Predict the Adhesion of Dairy Microorganisms To Solid Substrata

AbstractFour different thermodynamic approaches were compared on their usefulness to predict correctly the adhesion of two fouling microorganisms from dairy processing to various solid substrata. The surface free energies of the interacting surfaces were derived from measured contact angles according to:1.The equation of state;2.The geometric-mean equation using dispersion and polar components neglecting spreading pressures;3.The geometric-mean equation using dispersion and polar components while accounting for spreading pressures; and4.The Lifshitz-van der Waals/Acid-Base approach. All approaches yielded similar surface free energies for the low energy surfaces. Application of approach 1 with different liquids did not give consistent values for the high surface free energy substrata. The dispersion or Lifshiftz-van der Waals components were nearly equal for approaches 2, 3, and 4; however, the polar or acid-base components differed greatly according to the approach followed. Approaches 1 and 2 correctly predicted that adhesion should occur, although the trend with respect to the various solid substrata was opposite the one experimentally observed, as was also the trend predicted by approach 4. Only approach 3 correctly predicted the observed bacterial adhesion with respect to the various solid substrata. In approach 3 and 4, adhesion was frequently found, despite a positive free energy of adhesion. This was attributed to either possible local attractive electrostatic interactions, inadequate weighing of surface free energy components in the calculation of free energies of adhesion, or to additional forces arising from structured interfacial water.

Deposition of polystyrene particles in a parallel plate flow cell. 2. Pair distribution functions between deposited particles

Abstract Deposition of polystyrene particles is influenced by blocking effects and particle and collector heterogeneity. In order to study the influence of both effects, the distribution of polystyrene particles deposited on flat polymethylmethacrylate (PMMA), fluorethylenepropylene copolymers (FEP) and mica collector surfaces in a parallel plate flow cell has been investigated and was correlated with computer-simulated random distribution patterns. Radial pair distribution functions between deposited particles reveal that the deposition of particles near already deposited particles is unfavourable due to a blocking of up to 3 particle diameters. Furthermore preferential angular distributions were observed with respect to the flow direction. Finally, both radial and angular pair distribution functions suggest that the immobilization of deposited particles is more effective on PMMA than on FEP or mica.

THE INFLUENCE OF COLLECTOR AND BACTERIAL-CELL SURFACE-PROPERTIES ON THE DEPOSITION OF ORAL STREPTOCOCCI IN A PARALLEL PLATE FLOW CELL

Abstraet-The deposition of two strains of oral streptococci on collector surfaces with different surface free energies has been studied in a parallel plate flow cell at various buffer concentrations. One of the strains, Streptococcus salivarius HB, was characterized by the presence of proteinaceous surface appendages with lengths between 72 and 178 nm; whereas S. salivarius HB-C12, a spontaneous mutant of S. salivarius HB, was devoid of all surface appendages. Large differences were observed between the deposition rates of the two strains which were not predicted by theoretical calculations based on the convective diffusion equation using a DLVO-type potential function. This difference was attributed to the influence of the surface appendages of S. salivarius HB, which were absent on the mutant strain S. salivarius HB-C12. Furthermore, an additional attractive interaction, not accounted for in the DLVO theory, was needed in order to match the experimental deposition rates on the low surface free energy co...

Deposition of leuconostoc mesenteroides and streptococcus thermophilus to solid substrata in a parallel plate flow cell

Deposition of two microbial strains encountered in the dairy industry (Leuconostoc mesenteroides and Streptococcus thermophilus) to substrata with different wettabilities was studied in a parallel plate flow cell. Deposition was studied both from a bacterial suspension in water and in potassium phosphate buffer (pH 70). L. mesenteroides adhered rather weakly and showed no clear preference for any of the substrata. Conversely, S. thermophilus adhered much better to substrata with a high wettability than to low wettability substrata. Using real‐time image analysis, it was observed that after an initially high deposition of S. thermophilus from water to glass, cells subsequently desorbed leaving a biosurfactant layer on the surface to which freshly cultured cells did not adhere. Presumably this layer is due to biosurfactants produced by the adhering cells themselves. Such a biological anti‐adhesive coating might have great potential for the control of microbial fouling in dairy processing.

DEPOSITION OF POLYSTYRENE LATEX-PARTICLES TOWARD POLYMETHYLMETHACRYLATE IN A PARALLEL PLATE FLOW CELL

Abstract Deposition of micron sized polystyrene latex particles toward flat substrata is driven either by convective transport and diffusion or by a colloidal interaction controlled process. The differential equation governing particle transport in a parallel plate flow cell involving both processes has been solved, taking into account attractive and repulsive interaction forces as described by the DLVO theory. Therefore a combination of a numerical method and the Surface Force Boundary Layer Approximation was used. In order to test the validity of the model, the influence of colloidal interaction forces and flow velocity on deposition of two types of polystyrene particles has been measured experimentally in a parallel plate flow cell. It is argued that the model successfully describes deposition processes despite the measured deposition efficiency being a factor of 1.2–1.7 lower than theoretically predicted. It is suggested that the decreased deposition efficiency is mainly due to particle and substratum heterogeneities enabling deposition at low ionic strengths contradictory to model predictions.

Direct observations of cooperative effects in oral streptococcal adhesion to glass by analysis of the spatial arrangement of adhering bacteria.

The spatial arrangement of two strains of oral bacteria adhering on glass was studied in order to investigate cooperative effects in their adhesion mechanisms. Streptococcus salivarius HB was a strain which possessed several classes of fibrillar surface appendages, whereas on the cell surface of S. mutants NS no surface appendages could be identified. The bacteria were deposited from a flowing suspension with various buffer concentrations on the bottom glass plate of a parallel plate flow cell and were observed directly with a video camera mounted on a phase contrast microscope. The positions of all adhering bacteria were determined by means of automated real time image analysis and subsequently employed for calculating radial and angular pair distribution functions. Pair distribution functions indicate the average relative number density of bacteria around one deposited bacterium as a function of the radial distance or the angular orientation relative to the flow direction. From the calculated pair distribution functions of both bacterial strains it was concluded that cooperative effects contributed to the adhesion of S. salivarius HB, but not to adhesion of S. mutants NS. It was suggested that these cooperative effects originate from the surface appendages of S. salivarius HB.

EXPERIMENTAL APPROACHES FOR STUDYING ADHESION OF MICROORGANISMS TO SOLID SUBSTRATA - APPLICATIONS AND MASS-TRANSPORT

Abstract Various experimental systems have been developed which enable the study of adhesion of microorganisms to solid substrata. These systems can be distinguished in flow systems and static systems; in addition, static systems can be divided into systems with relatively small and large suspension volumes. It will be argued that a proper knowledge of the mechanisms of mass transport is required in order to fully understand the deposition process, a fact that has been largely negelected in the current literature. Furthermore, it should be noted that the adsorption kinetics are different for systems with relatively small and large suspension volumes. Therefore two different but analogous phenomenological description of adhesion kinetics are presented. Finally, it is concluded that flow systemscan be advantageously employed over static systems whenever qunatitative results are required, and especially since correlations with data from other types of flow systems can be made more easily. Static systems may be preferred when specific types of interactions are studied.

Infection resistance of degradable versus non-degradable biomaterials: an assessment of the potential mechanisms.

Extended life expectancy and medical development has led to an increased reliance on biomaterial implants and devices to support or restore human anatomy and function. However, the presence of an implanted biomaterial results in an increased susceptibility to infection. Due to the severity of the potential outcomes of biomaterial-associated infection, different strategies have been employed to reduce the infection risk. Interestingly, degradable biological materials demonstrate increased resistance to bacterial infection compared to non-degradable synthetic biomaterials. Current knowledge about the specific mechanisms of how degradable biological materials are afforded increased resistance to infection is limited. Therefore, in this paper a number of hypotheses to explain the decreased infection risk associated with the use of degradable versus non-degradable biomaterials are evaluated and discussed with reference to the present state of knowledge.

The potential for bio-optical imaging of biomaterial-associated infection in vivo

This review presents the current state of Bioluminescence and Fluorescent Imaging technologies (BLI and FLI) as applied to Biomaterial-Associated Infections (BAI). BLI offers the opportunity to observe the in vivo course of BAI in small animals without the need to sacrifice animals at different time points after the onset of infection. BLI is highly dependent on the bacterial cell metabolism which makes BLI a strong reporter of viable bacterial presence. Fluorescent sources are generally more stable than bioluminescent ones and specifically targeted, which renders the combination of BLI and FLI a promising tool for imaging BAI. The sensitivity and spatial resolution of both imaging tools are, however, dependent on the imaging system used and the tissue characteristics, which makes the interpretation of images, in terms of the location and shape of the illuminating source, difficult. Tomographic reconstruction of the luminescent source is possible in the most modern instruments, enabling exact localization of a colonized implant material, spreading of infecting organisms in surrounding tissue and immunological tissue reactions. BLI studies on BAI have successfully distinguished between different biomaterials with respect to the development and clearance of BAI in vivo, simultaneously reducing animal use and experimental variation. It is anticipated that bio-optical imaging will become an indispensable technology for the in vivo evaluation of antimicrobial coatings.