Analysis of Bacterial Detachment from Substratum Surfaces by the Passage of Air-Liquid Interfaces

Abstract

A theoretical analysis of the detachment of bacteria adhering to substratum surfaces upon the passage of an air-liquid interface is given, together with experimental results for bacterial detachment in the absence and presence of a conditioning film on different substratum surfaces. Bacteria (Streptococcus sobrinus HG1025, Streptococcus oralis J22, Actinomyces naeslundii T14V-J1, Bacteroides fragilis 793E, and Pseudomonas aeruginosa 974K) were first allowed to adhere to hydrophilic glass and hydrophobic dimethyldichlorosilane (DDS)-coated glass in a parallel-plate flow chamber until a density of 4 ؋ 10 6 cells cm ؊2 was reached. For S. sobrinus HG1025, S. oralis J22, and A. naeslundii T14V-J1, the conditioning film consisted of adsorbed salivary components, while for B. fragilis 793E and P. aeruginosa 974K, the film consisted of adsorbed human plasma components. Subsequently, air bubbles were passed through the flow chamber and the bacterial detachment percentages were measured. For some experimental conditions, like with P. aeruginosa 974K adhering to DDS-coated glass and an air bubble moving at high velocity (i.e., 13.6 mm s ؊1 ), no bacteria detached upon passage of an air-liquid interface, while for others, detachment percentages between 80 and 90% were observed. The detachment percentage increased when the velocity of the passing air bubble decreased, regardless of the bacterial strain and substratum surface hydrophobicity involved. However, the variation in percentages of detachment by a passing air bubble depended greatly upon the strain and substratum surface involved. At low air bubble velocities the hydrophobicity of the substratum had no influence on the detachment, but at high air bubble velocities all bacterial strains were more efficiently detached from hydrophilic glass substrata. Furthermore, the presence of a conditioning film could either inhibit or stimulate detachment. The shape of the bacterial cell played a major role in detachment at high air bubble velocities, and spherical strains (i.e., streptococci) detached more efficiently than rod-shaped organisms. The present results demonstrate that methodologies to study bacterial adhesion which include contact with a moving air-liquid interface (i.e., rinsing and dipping) yield detachment of an unpredictable number of adhering microorganisms. Hence, results of studies based on such methodologies should be referred as "bacterial retention" rather than "bacterial adhesion".

Surface plasmon resonance shows that type IV pili are important in surface attachment by Pseudomonas aeruginosa

“…Similarly, endpoint assays of biofilm formation in PVC microtitre plates (figure 3) also showed a significant difference between wild-type and pil mutant biofilms (one-way ANOVA: F 2,21 Z46.66, p!0.001) but SPR and surface attachment of type IV pili A. T. A. Jenkins and others 257 again failed to distinguish between the pilA and pilT mutants themselves (two-sample t-test: pO0.5). We note that direct comparison of these visual assays with the SPR protocol is not strictly possible as the visual protocol involves additional passages through an airwater interface, which can substantially re-arrange biofilm structure (Gomez-Suarez et al 2001). However, we do not feel that this invalidates the comparisons between the behaviour of the wild-type and mutant bacteria.…”

Unusual swelling of a polymer in a bacterial bath

“…Our case of a flexible polymer chain is therefore one of the simplest key examples to proceed along this important direction. Third, in general, the set-up we are proposing is realizable in experiments and relevant for biological systems where swarms of bacteria are moving close to flexible objects like at water-air interfaces [56][57][58][59][60][61]. Our two-dimensional model can indeed be realized e.g.…”

Efficient elusion of viable adhesive cells from a microfluidic system by air foam

“…Figure 9 shows the micrographs of DLD1 after immune-staining phase, showing DLD1 could be labeled with antibodies directed against cytokeratins and the nuclear dye Although it is not fully understood what is the mechanism of using air foam to release cell bound to the lumen of microfluidic devices that are immobilized with antibody functionalized SLB film, the model of air-water interface detaching bacteria adhered to a surface helps us realize these multi-physical phenomena. 33 Based on this model, the air-water interfacial force used to detach cells is closely related to interfacial tension and the position of a three-phase contact between a cell, air, and liquid, and it ranges from 0.02 dyn to 0.4 dyn. Exposed to the force, cell might be damaged in release phase.…”