The surface physicochemistry and adhesiveness of Shewanella are affected by their surface polysaccharides

Abstract

Shewanella strains have previously been studied with regard to their cell surface ultrastructure and LPS composition. They have now been further characterized with respect to their surface physicochemistry and ability to adhere to haematite. The surfaces of the Shewanella strains were found to be electronegative and hydrophilic, and these properties could be correlated with LPS composition or the presence of capsular polysaccharides. Strains expressing rough LPS with no capsule were more hydrophobic and electronegative than those possessing smooth LPS or capsules. By combining different approaches, such as contact-angle measurement, hydrophilic/ hydrophobic chromatography, microelectrophoresis, adhesion assays and calculation of interaction energies, it was shown that electrostatic interactions predominate over hydrophobic interactions at the cell-iron oxide interface. Bacterial adhesion to haematite was significantly reduced in strains expressing smooth LPS or a capsule. These findings remained true for Shewanella strains grown under either aerobic or anaerobic conditions, although the surfaces of anaerobic cells appeared to be less electronegative and more hydrophilic than those of aerobic cells.

Biogeochemical Controls on the Product of Microbial U(VI) Reduction

“…Unlike many Gram-negative bacteria, including most Shewanella strains with ζ values ranging from −30 to −40 mV, S. oneidensis MR-1 cells possess a relatively low surface charge: a few mV at circumneutral pH and an ionic strength of 0.01. 35 Our results confirm previous findings (Table 2), with surface charge values ranging from −3.2 to −3.9 mV for S. oneidensis MR-1 in the initial stage of the experiment. Interestingly, the zeta potential becomes more negative during the course of microbial U(VI) reduction.…”

Disruption of Putrescine Biosynthesis in Shewanella oneidensis Enhances Biofilm Cohesiveness and Performance in Cr(VI) Immobilization

“…Previous studies demonstrated that cell surface charges and hydrophobicity play an important role in cell adhesion to biotic and abiotic surfaces (25,41,42). Hydrophobic interactions have been shown to be an important factor controlling the adhesion of Shewanella cells to amorphous Fe(III) oxide (41).…”

“…Hydrophobic interactions have been shown to be an important factor controlling the adhesion of Shewanella cells to amorphous Fe(III) oxide (41). Comparative analyses of the abilities of several different Shewanella strains to adhere to hematite (␣-Fe 2 O 3 ) revealed that strains with more hydrophobic and electronegative cell surfaces exhibited better adhesion (42). In addition, Shewanella cells with a more hydrophobic and electronegative surface have been shown to enhance not only cell adhesion to graphite electrodes but also cell-cell adhesion as evidenced by strong autoaggregation (25).…”

Differential Lipopolysaccharide Core Capping Leads to Quantitative and Correlated Modifications of Mechanical and Structural Properties in Pseudomonas aeruginosa Biofilms

“…For the measurement of contact angles, a sessile drop technique based on the method of Korenevsky and Beveridge was performed (27). Briefly, overnight cultures of P. aeruginosa cells were harvested and washed twice with a sterile buffer (0.1 M NaCl-0.05 M HEPES [pH 7.4]) and adjusted to an OD 600 of 1.0 in a 10-ml volume of the buffer.…”