Effects of nutrients on exopolysaccharide production and surface properties of Aeromonas salmonicida

Abstract

Extracellular polysaccharide (EPS) and capsular polysaccharide (CPS) production by Aeromonas sabnonicida A450 and the influence of the capsule on cell surface properties were studied. A. salmonicida did not produce CPS or EPS when glucose, phosphate, magnesium chloride, or trace mineral components were absent from the medium. The addition of yeast extract improved capsule production. Neither EPS nor CPS formation depended on the C/N ratio, although it appeared to be influenced by the level of carbon and nitrogen in the culture. Both EPS and CPS production started at the end of the logarithmic growth phase. The amounts of EPS and CPS produced were not influenced by temperature changes between 15 and 20°C and was maximal from pH 7 to 7.5. Cell surface properties were strongly influenced by capsule production; high CPS production was associated with enhanced cell hydrophilicity and autoagglutination. The effect of CPS on cell surface properties was independent of the presence of the surface protein array (A-layer). Aeromonas salmonicida causes fish furunculosis, an infectious disease principally of salmonid fish (16, 17). Virulent strains produce a surface protein array (A-layer) (9), which is crucial to the virulence of this organism (6) and has been found to be associated with an increase in cell surface hydrophobicity (25). Interactions between bacteria and their environment, including pathogenic phenomena, normally involve specific interactions between macromolecules found on bacterial and host cell surfaces (19). The macromolecular components of bacterial surfaces, e.g., lipopolysaccharide (LPS), protein, and exopolymers, have been shown to vary in quantity and composition with growth conditions (3). Changes in cell wall or polymer composition have a strong influence on the physicochemical properties of the cell surface, e.g., via differences in hydrophobicity (13). Recently, Garrote et al. (5) have demonstrated the production by A. salmonicida of completely cell-detached extracellular polysaccharide (EPS) and cell-bound capsular polysaccharide (CPS). Since capsular polysaccharide is found on the bacterial surface, we proposed to assess the influence of this CPS on A. salmonicida cell surface properties. The aim of our work was also to study the effects of growth medium composition and environmental conditions on the formation of exopolysaccharides (sum of EPS and CPS) byA. salmonicida. MATERIALS AND METHODS Organisms. A. salmonicida strains used in this study were

Adhesion of Acinetobacter venetianus to Diesel Fuel Droplets Studied with In Situ Electrochemical and Molecular Probes

“…The three-dimensional network of the CPS hydro-gel entangles nanometer-sized fuel droplets, which do not coalesce, and stabilizes the emulsion without reducing the interfacial tension (10). This finding disagrees with other reports (4,21), where it was demonstrated that CPS hinders attachment to hydrophobic solid surfaces.…”

Effect of Chromium and Organic Acids on Microbial Growth and Exopolymeric Substance Production by Pseudomonas Bacteria

“…This pH dependence of EPS production has also been observed by other strains [16,17]. For example, Bonet et al [18] reported that the maximum amount of EPS production by Aeromonas salmoicida was observed at pH valuess between 7 and 7.5. Similarly, Kilic and Donmez [17] found that a solution pH of 7 was required to obtain a maximum EPS yield by P. aeruginosa.…”

Composition of the sheath produced by the green alga Chlorella sorokiniana

“…Parker et al (1996) observed that metal cations affected the viscosity of the capsular polysaccharide (CPS) produced by M. flos-aquae C3-40. It was also reported that Aeromonas salmonicida did not produce extracellular polysaccharides or CPS when magnesium chloride was absent in the medium (Bonet et al 1993). We predict that Mg 2+ plays an important role in the formation and morphological characteristics of the mucilage sheath excreted by C. sorokiniana.…”

“…Therefore, we investigated the chemical composition of the sheath produced by C. sorokiniana. Generally, hydrolysis of sheath matrix can be performed using some chemicals such as trifluoroacetic acid, HCl, H 2 SO 4 or NaOH (Cupac and Gantar 1992;Bonet et al 1993;Emerson and Ghiorse 1993b;Gutiérrez et al 1996;Ricci et al 2001;Chiovitti et al 2003). Emerson and Ghiorse (1993b) reported that treatment of the sheath with NaOH resulted in rapid breakdown, while treatment with HCl resulted in slow but significant hydrolysis.…”