Mobile and immobile adhesion of staphylococcal strains to hydrophilic and hydrophobic surfaces
Boks, N.P. ; Kaper, H.J. ; Norde, W. ; Mei, H.C. van der; Busscher, H.J. - \ 2009
Journal of Colloid and Interface Science 331 (2009)1. - ISSN 0021-9797 - p. 60 - 64.
bacterial adhesion - biofilm reactors - infections - attachment - deposition - reversibility - substrata - energies - system - flow
Staphylococcus epidermidis adheres to hydrophilic glass and hydrophobic dimethyldichlorosilane (DDS)-coated glass in similar numbers, but in different modes. Real-time observation of staphylococcal adhesion under a shear rate of 15 s(-1) revealed different adhesion dynamics on both substrata. The number of adsorption and desorption events to achieve a similar number of adhering bacteria was twofold higher on hydrophilic than on hydrophobic DDS-coated glass. Moreover. 22% of all staphylococci on glass slid over the surface prior to adhering on a fixed site ("mobile adhesion mode"), but mobile adhesion was virtually absent (1%) on DDS-coated glass. Sliding preceded desorption on hydrophilic glass in about 20% of all desorption events, while on hydrophobic DDS-coated glass 2% of all staphylococci desorbed straight from their adhesion site. Since acid-base interactions between the staphylococci and a hydrophobic DDS-coating are attractive, it is suggested that these interactions facilitate a closer approach of the bacteria and therewith enhance immobile adhesion at local, high affinity sites. Alternatively, if the local site is low affinity, this may lead to desorption. In the absence of attractive acid-base interactions, as on hydrophilic glass, bacteria can be captured in the minimum of the DLVO-interaction energy curve, but this does not prevent them from sliding under flow at a fixed distance from a substratum surface until immobilization or desorption at or from a local high or low affinity site, respectively.
Design and operation of nitrifying trickling filters in recirculating aquaculture: a review
Eding, E.H. ; Kamstra, A. ; Verreth, J.A.J. ; Huisman, E.A. ; Klapwijk, A. - \ 2006
Aquacultural Engineering 34 (2006)3. - ISSN 0144-8609 - p. 234 - 260.
fixed-film nitrification - fish culture systems - biofilm reactors - water-treatment - temperature - performance - ph - effluents - discharge - impact
This review deals with the main mechanisms and parameters affecting design and performance of trickling filters in aquaculture. Relationships between nitrification rates and easily accessible process parameters, like bulk phase concentration of TAN, O2, organic matter (COD), nitrite, temperature, HCO3¿, pH and the hydraulic loading of the trickling filter, are discussed in relation to the design and operation of such filters. Trickling filter design procedures are presented and one of them, a model describing the nitrification performance of trickling filters by plug-flow characteristics, is discussed in greater detail. Finally, practical aspects in relation to filter design and operation are presented