Characterization of the Lipopolysaccharides and Capsules of Shewanella spp

Abstract

Electron microscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis with silver staining and 1 H, 13 C, and 31 P-nuclear magnetic resonance (NMR) were used to detect and characterize the lipopolysaccharides (LPSs) of several Shewanella species. Many expressed only rough LPS; however, approximately one-half produced smooth LPS (and/or capsular polysaccharides). Some LPSs were affected by growth temperature with increased chain length observed below 25°C. Maximum LPS heterogeneity was found at 15 to 20°C. Thin sections of freeze-substituted cells revealed that Shewanella oneidensis, S. algae, S. frigidimarina, and Shewanella sp. strain MR-4 possessed either O-side chains or capsular fringes ranging from 20 to 130 nm in thickness depending on the species. NMR detected unusual sugars in S. putrefaciens CN32 and S. algae BrY DL . It is possible that the ability of Shewanella to adhere to solid mineral phases (such as iron oxides) could be affected by the composition and length of surface polysaccharide polymers. These same polymers in S. algae may also contribute to this opportunistic pathogen's ability to promote infection.Shewanella organisms are generally associated with aquatic habitats and play important roles in the cycling of particulate iron and organic matter, but they can also be opportunistic pathogens (33,45). Because of their environmental significance, they are presently under vigorous investigation and many new species were recently included in the genus (45). Most Shewanella organisms are capable of dissimilatory reduction of a wide range of electron acceptors, including metal oxides [e.g., those of Fe(III) and Mn(IV)]. Several reductive mechanisms are possible. Electron flux from the organism to the solid oxide may occur via (i) direct contact of bacterial outer membrane and oxide surface (2, 9, 21, 31), (ii) organic shuttles (such as humic acids or quinones to mediate electron flow (22, 32), or (iii) a combination of both processes. For the direct contact model, metal reductases (such as c-type cytochromes) seem to be embedded in the outer membrane of dissimilatory metal-reducing bacteria to facilitate electron flow (13,29,30). Lipopolysaccharide (LPS) and outer membrane proteins could play principal roles in establishing and maintaining contact with oxide minerals so that electron transport to the terminal acceptor occurs. The junction between cell and mineral must be tight so as to ensure that the reductase functions effectively (23). However, the cell surface structure and LPS of Shewanella, which could affect the cell-mineral connection, are poorly understood (28,39,40,48). In this present article we characterize those structural elements that can extend beyond the outer face of the outer membrane, i.e., the LPS O-side chains and capsular polymers.Bacterial strains and growth conditions. The strains used in this study are shown in Table 1. Most of these strains were kindly provided by Doug Lies (Jet Propulsion Laboratory, Pasadena, Calif.). S. algae BrY was supplied by both D. Lies an...

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

“…We too often consider this membrane to be a homogeneous static assembly of macromolecules that are randomly dispersed over the bilayer surface. Instead, all molecules are in dynamic motion and it is probable that, at distinct time intervals, a mosaic of molecular patches of definite polarity and charge exists (Amro et al, 2000;Sokolov et al, 2001;Korenevsky et al, 2002;Vadillo-Rodriguez et al, 2004a). Given an inanimate surface of consistent hydrophobicity (such as the HIC Sepharose beads), the tendency of the OM surface would be to congregate and align compatible macromolecules towards the inanimate surface.…”

The product of microbial uranium reduction includes multiple species with U(IV)–phosphate coordination

“…Numerous Shewanella spp. are known to contain lipopolysaccharides with phosphoryl-poor O-antigens that extend from the core polysaccharide at the cell membrane-solution interface (Korenevsky et al, 2002). S. oneidensis MR-1 is notable in that it lacks entirely the O-polysaccharides (Vinogradov et al, 2003), leaving the phosphoryl-rich core regions relatively exposed.…”

“…Phosphoryl sites are expected to be present on cell surfaces in lipopolysaccharides (Langley and Beveridge, 1999;Korenevsky et al, 2002). In addition, we expect EPS to have been produced during our incubations .…”

Shewanella putrefaciens – a new opportunistic pathogen of freshwater fish

“…Depending on the length of O-specific chain, two types of LPS are observed: the smooth LPS (S-LPS) which contains the O-antigenic side chain and rough LPS (R-LPS), which does not contain side chains of the O-antigen or they are reduced (4). R-LPS without O-chains was described in S. putrefaciens (21,28). The reduced lipopolysaccharide structure allows for better adhesion of bacteria to the iron-containing surface, and therefore more efficient use of this metal as an electron acceptor in respiration.…”

“…The reduced lipopolysaccharide structure allows for better adhesion of bacteria to the iron-containing surface, and therefore more efficient use of this metal as an electron acceptor in respiration. The core of LPS has high concentrations of carboxyl and phosphoryl sites, which indicate the polarity, and contribute to the interaction with metal ions (21). In addition, the LPS of S. putrefaciens predisposes these bacteria to form biofilms on iron surface, and also enables to use this metal in their metabolic pathways.…”