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Infect. Immun., 05 1995, 1698-1702, Vol 63, No. 5
M van Raamsdonk, HC van der Mei, JJ de Soet, HJ Busscher and J de Graaff
In this study, the effect of antibody adsorption on physicochemical
properties of Streptococcus sobrinus was studied. Bacteria were
preincubated with polyclonal antibodies or with OMVU10, a monoclonal
antibody (MAb) reactive with S. sobrinus. The zeta potentials and the
hydrophobicity as determined by microbial adhesion to hydrocarbons were
measured in potassium phosphate buffer with a pH ranging from 2 to 9. S.
sobrinus preincubated with polyclonal antibodies was positively charged at
pH 2, 3, and 4 and had an isoelectric point at pH 4.8. Untreated S.
sobrinus cells or cells preincubated with MAbs were negatively charged over
the whole pH range. X-ray photoelectron spectroscopy showed a decrease in
O/C and P/C ratios for bacteria preincubated with polyclonal antibodies. A
combination of the pH- dependent zeta potential and the X-ray photoelectron
spectroscopy data of the overall chemical composition of the cell surface
suggests that polyclonal antibody adsorption occurs through blocking of
surface phosphate. The measurement of hydrophobicity by microbial adhesion
to hydrocarbons revealed that S. sobrinus preincubated with polyclonal
antibodies was hydrophobic (90% of the bacteria bound to hexadecane),
whereas the controls were relatively hydrophilic. S. sobrinus preincubated
with OMVU10 was found to be more hydrophobic than the controls at pH 5 and
7. Hydrophobicity as measured by water contact angles showed an increase in
hydrophobicity when S. sobrinus was preincubated with polyclonal
antibodies. The epitopes to which the antibodies are directed were
visualized by immunogold labeling and electron microscopy. The results
suggested that OMVU10 is reactive with only a few epitopes of the cell
surface, whereas polyclonal antibodies were found to be reactive with many
epitopes. In conclusion, adsorption of polyclonal antibodies was found to
influence the overall physicochemical surface properties of the organism,
probably by forming a coating over the whole cell surface. Adsorption of
MAbs was more localized, which could explain their lesser influence on
these surface properties.
Copyright © 1995, American Society for Microbiology
Effect of polyclonal and monoclonal antibodies on surface properties of Streptococcus sobrinus
Department of Oral Microbiology, Academic Centre for Dentistry Amsterdam, The Netherlands.
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