Relationship between Particle Size and Biological Activity of E. coli Boivin Endotoxin*

Abstract

Many investigators have tried unsuccessfully to demonstrate that a specific chemical structure is responsible for the toxic action of bacterial endotoxins. Practically all of the protein (or peptide) and lipid constituents of the endotoxin molecule may be removed without affecting significantly its biological activities, and the carbohydrate moiety loses toxicity after it is depolymerized by even mild acid hydrolysis (1-4). Recent studies have also shown that toxicity does not depend upon the presence of the polysaccharide side chains that give the endotoxin its O-antigenic specificity (5).Other observations indicate that the size of the molecule, or molecular aggregate, is a more prominent determinant of toxicity than the chemical composition (6-7). Variations in particle size were noted by Schramm, Westphal, and Luderitz (8) in studies involving electron microscopy, sedimentation in the ultracentrifuge, and viscosity measurements. They demonstrated that endotoxins in solution are polydisperse, and the average particle weight was estimated at 24 million. The larger particles are formed by aggregation of identical subunits with a molecular weight of about 1 million.The purpose of the present work was to get more quantitative information about the polydispersity of a Boivin endotoxin by sucrose density gradient centrifugation of endotoxin labeled uni-

RELATION OF STRUCTURE TO FUNCTION IN BACTERIAL O‐ANTIGENS. V. NATURE OF ACTIVE SITES IN ENDOTOXIC LIPOPOLYSACCHARIDES OF SERRATIA MARCESCENS*

“…The evaluation of this striking reactivity of endotoxin for what seems to be a diverse group of mostly basic organic substances, the role of particle size, the presence of ester groups, and the recently reported physical and chemical heterogeneity Beer et al, 1966) in the overall mechanism of endotoxin action is indeed an arduous task. If one assumes that in order for endotoxin to exhibit its toxic effects, a combination must occur between the endotoxin and the target cell(s) or target-cell components, one may speculate that the striking adhesion and reactivity of endotoxin may play a role in this attachment.…”

Purification and Physico-Chemical Analysis of Fractions from the Culture Supernatant of Escherichia coli O78K80: Free Endotoxin and a Non-Toxic Fraction

“…at 100') destroyed virtually all the toxicity of Ribi's endotoxin and produced a parallel decrease in the average sedimentation coefficient of the solute, although the 'acid hapten' obtained by this process (s = 1.4 S) retained certain antigenic characteristics of the parent endotoxin (Ribi et al 1962). By using non-hydrolytic conditions of disaggregation, in solutions containing sodium dodecylsulphate (SDS), two groups of workers reached opposite conclusions : Oroszlan & Mora (1963) found that the endotoxic complex of Serratia marcexens dissociated into particles of about 3 S, with significant concomitant decrease in the biological activity responsible for tumour damage; on the other hand, Beer, Staehelin, Douglas & Braude (1965) found that an endotoxic preparation from Escherichia coli could be treated with SDS without measurable loss of toxicity.…”

The Influence of Bacteriocins on Resistance to Infection by Gram-negative Bacteria. I. The Effect of Colicin on Bactericidal Power of Blood*

“…The present experiments were undertaken on the premise that production of colicin within cellophane sacs would exclude the large nondialyzable macromolecules of endotoxin (14). The preparations obtained in this fashion showed neither the toxic nor immunologic properties of the somatic antigen obtained from the colicinogenic strain of E. coli.…”