Control of Adhesion and Removal of Bacterial Cells from Stable Suspension Using Surface Characteristics

Abstract

Rapid collection and removal of gram-negative heterotrophic bacterial strain, Escherichia coli, was investigated by utilizing the interfacial interaction between cell and solid substratum. Both E.coli collection from stable suspension and its successive removal were performed by a column bed packed with fibrous ferro-nickel slag, which was employed as the collector media of bacterial cells. In the cell collection tests, little cell recovery was obtained at neutral pH condition where both E.coli and FS had negative surface potential. On the other hand, E.coli collection gradually increased as the pH decreased. These findings were explained by the suppression of electrostatic repulsive interaction between E.coli and FS led to an improvement in cell attachment to FS surface. Cell collection capacity Γ max exponentially increased as the interfacial interaction energy minimum V min became lower, indicating that surface characteristics played crucial roles in cell attachment mechanism. Moreover, part of the E.coli cells that had adhered to FS surface were effectively removed when the eluting solutions were alkaline conditions; hence reversible cell detachment from FS was possible by controlling the electro-repulsive force. Cyclic E.coli collection/removal tests demonstrated that cell collection and successive removal were repeatedly carried out al least six times, although about 40 mg of E.coli cell made a firm and irreversible attachment on FS. E.coli collection/removal behaviors in the present experiments were generally in good agreement with electrokinetic properties of cell and FS, suggesting that cell recovery based on surface characteristics is a promising method, especially for stable bacterial suspension.

In situ biochemical characterization of Venus cloud particles using a life-signature detection microscope

“…Additionally, to obtain good images with the LDM in acidic conditions, it is necessary to capture possible bacterial cells onto a target plate and prevent cell coagulation. This should be feasible because at a lower pH (pH 4), bacterial cells tend to attach to the surface without coagulation because of decreased electrostatic repulsion (Hayashi et al 2004). Through our experiments, Acidithiobacillus ferrooxidans did not lose their cell structure (i.e., remained round) nor DNA structure (stained by fluorescent dye after pH adjustment) when suspended in concentrated sulfuric acid at least for 10 min.…”