Adhesive extracellular polymers of Hyphomonas MHS-3: Interaction of polysaccharides and proteins

The adsorption behavior of extracellular polymeric substances (EPS) from the marine bacterium Hyphomonas MHS-3 was investigated using attenuated total reflection Fourier transform infrared (ATR/FT-IR) spectrometry. The protein fraction of the crude EPS (EPS(c)) (propanol precipitated/extracted with EDTA) dominated the adsorption onto the germanium substratum Removal of the Protease K accessible portion of the EPS(c) protein, and treatment with RNase and DNase, yielded a hygroscopic substance (EPS(p)) which contained at least one adhesive polysaccharide component. Conditioning the substratum with EPS(c) diminished adsorption of the polysaccharide fractions in EPS(p); pre-adsorbed EPS, protein was nor displaced. The rate of EPS(c) adsorption on substrata conditioned with EPS(p) was slower than to clean germanium; however, the projected surface coverage of protein after long times, based on an empirical datafit, was the same as that for a clean substratum; the EPS(c) proteins did nor displace the pre-adsorbed adhesive polysaccharide fraction. SDS-PAGE (Coomassie blue stain) revealed an extensive homology between proteins from cell lysates and EPS(c) proteins. However, distinct differences in the banding pattern suggested that proteins did not originate primarily from cell lysis during tile extraction procedure. The results indicate that adhesive components of EPS, with respect to a hydrophilic surface (germanium), can be either protein or polysaccharide and that they may compete for interfacial binding sites.