Preservation of capsular material of streptococcal cells by specific lectins determined by immunoelectron microscopy

Abstract

We describe the use of lectins as specific stabilizing agents for the polysaccharide capsular components of two Gram-positive bacteria, Streptococcus agalactiae and Streptococcus bovis. Treatment of bacterial suspensions with wheatgerm agglutinin and concanavalin A allowed better morphological preservation as well as immunoelectron microscopic localization of a capsular component (lipoteichoic acid) by employing specific antibodies and the protein A-gold technique. Data obtained indicate that lectins are useful agents in preserving highly water-soluble capsular components during the electron microscopy procedures for both unembedded and embedded samples.

Ultrastructure of surface components of Streptococcus gallolyticus (S. bovis) strains of differing virulence isolated from pigeons

“…The presence of a capsule has also been described in S. bovis, presumably S. gallolyticus, isolates from cattle, sheep (Garvie & Bramley, 1979;Medrek & Barnes, 1962) and humans (Molinari et al, 1988), as well as in numerous other streptococci such as…”

“…Ruthenium red is a polycationic dye with specificity for polycationic polymers such as acidic polysaccharides. Although it has been widely used to stain bacterial capsular polysaccharides, ruthenium red does not protect capsular material against collapse and condensation, except when attachment to surfaces anchors the fibres and maintains their extended configuration, or when the capsule is stabilized by specific antibodies or lectins (Costerton et al, 1981;Jacques & Foiry, 1987;Molinari et al, 1988).…”

“…Except for some limited studies in human (Molinari et al, 1988) and ruminant (Semjkn & Galfi, 1990) strains, ultrastructural studies of this bacterial species have not been performed on isolates from any of these hosts. The present paper describes the ultrastructure of 15 pigeon S. gallolyticus strains.…”

Comparison of Alcian blue and ruthenium red effects on preservation of outer envelope ultrastructure in methanotrophic bacteria

“…Often as a result of this composition, considerable negative charges are present in the bacterial envelope. These layers are also highly hydrated (Costerton et al, 1981; Costerton et al, 1987; Molinari et al, 1988).…”

“…Many EM preparative procedures fail to optimally preserve components of the bacterial envelope, either by loss or collapse during dehydration stages (Costerton, 1980; Molinari et al, 1988;Roth, 1977) or insufficent stabilization during fixation (Progulske and Holt, 1980). Attempts to preserve and stabilize these delicate layers have included use of specific lectins (Molinari et al, 19881, specific antibodies alone (Molinari et al, 1987;Progulske and Holt, 1980) or in combination with ruthenium red (RR) (Mackie et al, 1979;Patterson et al, 19751, RR alone (Fassel et al, 1990;Luft, 1971aLuft, , 1971b; Progulske and Holt, 1980;Titus et al, 1982) and alcian blue (AB) (Progulske and Holt, 1980).…”