Adsorption of microbial cells to surfaces

The contamination of pharmaceutical suspensions for oral use is a cause of concern. The behaviour of organisms in such suspensions therefore needs to be examined before interpretation of experimental results can be undertaken. Under some conditions, bacteria may be strongly adsorbed and therefore more resistant to the effects of preservatives in other cases, the bacteria may be free in suspension. 

Two distinct phases of bacterial adsorption onto glass have been observed the first, reversible, phase may be interpreted in terms 

Sorption of microbial cells is selective but there is no obvious relation between Gram-staining characteristics and attachment, in Fig. 7.41, bacterial cells are shown adsorbing onto larger solid particles (a) or free in suspension (b) (c) illustrates the opposite effect -small particles are shown adsorbed onto bacterial cells. The bacterial cells are adsorbed onto flocculated particles in (d), onto solid surfaces in (e) (f)-(i) show the more complicated behaviour of bacterial forms with coats, cilia and flagella. The adsorption affects growth partly by masking the cell surface and 

Reproduced from D. Zvyagintsev, Interaction between Microorganisms and Solid Surfaces, Moscow University Press, Moscow, 1 973. 

In addition to the van der Waals and electrical forces, steric forces resulting from pro-tmding polysaccharide and protein molecules affect interactions specific interactions between charged groups on the cell surface and on the solid surface, hydrogen bonding or the formation of cellular bridges may all occur to complicate the picture. The ten possible forces of interaction between cells and surfaces have been listed as  

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