Adhesive extracellular polymers of hyphomonas mhs-3: interaction of polysaccharides and proteins

Abstract

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 (EPSC) (propanol precipitated/extracted with EDTA) dominated the adsorption onto the germanium substratum. Removal of the Protease K accessible portion of the EPSC protein, and treatment with RNase and DNase, yielded a hygroscopic substance (EPSP) which contained at least one adhesive polysaccharide component. Conditioning the substratum with EPSC diminished adsorption of the polysaccharide fractions in EPSP; pre‐adsorbed EPSC protein was not displaced. The rate of EPSC adsorption on substrata conditioned with EPSP 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 EPSC proteins did not displace the pre‐adsorbed adhesive polysaccharide fraction. SDS‐PAGE (Coomassie blue stain) revealed an extensive homology between proteins from cell lysates and EPSC proteins. However, distinct differences in the banding pattern suggested that proteins did not originate primarily from cell lysis during the 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.