Many Staphylococcus epidermidis strains possess capsule or slime layers and consequently the staphylococcal cell surface should be regarded as a soft, polyelectrolyte layer allowing electrophoretic fluid flow through a layer of fixed charges. The presence of such a soft layer decreases the energy barrier due to electrostatic repulsion in the interaction of the organisms with negatively charged substrata [Morisaki, H., Nagai, S., Ohshima, H., Ikemoto, E. & Kogure, K. (1999), Microbiology 145, 2797–2802] and hence plays an important role in their adhesion. In this paper, the authors compare the electrophoretic softness and amount of fixed charge in the outer cell surface layers of 20 S. epidermidis strains, grown in a liquid medium or on a solid agar, as determined from the dependencies of their electrophoretic mobilities upon the ionic strength of a suspending fluid. Most of the staphylococcal cell surfaces were relatively soft, with a mean cell surface softness (1/λ) for strains grown in liquid medium of 1·7±0·6 nm (standard deviation over all 20 strains) which is soft by comparison with a completely bald, peptidoglycan-rich streptococcal cell surface (1/λ=0·7 nm). When the staphylococcal strains were grown on solid agar, the cell surface softness of 17 of the 20 strains increased, sometimes by a factor of two. On average for 20 strains, the cell surface softness increased significantly (P<0·05, Student’s t-test) to 2·8±1·8 nm. The amount of fixed charge in the outer cell surface layer was −28±9 mM for bacteria grown in liquid medium and −24±12 mM for bacteria grown on agar. A soft, highly negatively charged polyelectrolyte layer was inferred by microelectrophoresis for all the staphylococcal cell surfaces, regardless of whether staining had indicated the presence of a capsule or slime layer.
BosR.,
BusscherH. J,
Van der MeiH. C.1998; ‘‘Soft particle’’ analysis of the electrophoretic mobility of a fibrillated and non-fibrillated oral streptococcal strain: Streptococcus salivarius. Biophys Chem 74:251–255[CrossRef]
BosR.,
BusscherH. J,
Van der MeiH. C.1999; Physico-chemistry of initial microbial adhesive interactions – its mechanisms and methods to study. FEMS Microbiol Rev 23:179–230
ChristensenG. D.,
SimpsonW. A.,
BisnoA. L.,
BeachyE. H.
1982; Adherence of slime-producing strains of Staphylococcus epidermidis to smooth surfaces. Infect Immun 37:318–326
HiemenzP. C.
1977; Electrophoresis and other electrokinetic phenomena. In Principles of Colloid and Surface Chemistry pp 452–487 Edited by
LagowskiJ. J.
New York: Marcel Dekker;
JuckerB. A.,
HarmsH.,
ZehnderA. J. B.
1996; Adhesion of the positively charged bacterium Stenotrophomonas (Xanthomonas) maltophilia 70401 to glass and Teflon. J Bacteriol 178:5472–5479
KawahataS.,
OhshimaH.,
MuramatsuN.,
KondoT.
1990; Charge distribution in the surface region of human erythrocytes from electrophoretic mobility data. J Colloid Interface Sci 138:182–186[CrossRef]
MorisakiH.,
NagaiS.,
OhshimaH.,
IkemotoE.,
KogureK.
1999; The effect of mobility and cell-surface polymers on bacterial attachment. Microbiology 145:2797–2802
PoortingaA. T.,
BosR.,
BusscherH. J.
2001; Electrostatic interactions in the adhesion of an ion-penetrable and ion-impenetrable bacterial strain to glass. Colloids Surf B: Biointerfaces 20:105–117[CrossRef]
Van der MeiH. C., Van de Belt-GritterB.ReidG.,
Bialkowska-HobrzanskaH.,
BusscherH. J.
1997; Adhesion of coagulase-negative staphylococci grouped according to physico-chemical properties. Microbiology 143:3861–3870[CrossRef]
Van der MeiH. C.BusscherH. J.,
BosR.,
De VriesJ.,
BoonaertC. J. P.,
DufreneY. F.
2000; Direct probing by atomic force microscopy of the cell surface softness of a fibrillated and nonfibrillated oral streptococcal strain. Biophys J 78:2668–2674[CrossRef]
Van PeltA. W. J.,
WeerkampA. H.,
UyenM. H. W. J. C.,
BusscherH. J.,
De JongH. P.,
ArendsJ.
1985; Adhesion of Streptococcus sanguis to polymers with different surface free energies. Appl Environ Microbiol 49:1270–1275
WeerkampA. H.,
HandleyP. S.,
BaarsA.,
SlotJ. W.
1986; Negative-staining and immunoelectron microscopy of adhesion-deficient mutants of Streptococcus salivarius reveal that the adhesive protein antigens are separate classes of cell surface fibrils. J Bacteriol 165:746–755
WitP. J.,
NoordmansJ.,
BusscherH. J.
1997; Tracking of colloidal particles using microscopic image sequence analysis. Application to particulate microelectrophoresis and particle deposition. Colloids Surf A: Physicochem Eng Aspects 125:85–92[CrossRef]