Electron microscopy of endotoxic lipopolysaccharide from Bacteroides, Fusobacterium and sphaerophorus.

Abstract

Lipopolysaccharide endotoxins (LPS) obtained by phenol‐water extraction of Bacteroides melaninogenicus, B. fragilis, Fusobacterium and Sphaerophorus and positively stained with uranyl acetate were studied in the electron microscope. The LPS particles had characteristic morphological features comparable to those of LPS from other anaerobic as well as aerobic Gram‐negative bacteria. LPS particles from B. melaninogenicus and Fusobacterium mostly appeared as discs delimited by a single or a triple‐layered surface structure. The preparations also contained rod‐like particles exhibiting a similar trilaminar structure. LPS particles from B. fragilis and Sphaerophorus appeared mainly as rods. In addition, LPS prepared from Sphaerophorus contained long ribbon‐like structures. Different ways of purification, or differences in chemical structure of the basal polysaccharide core of the LPS, seemed to have no discernible effects on the morphology of the extracted particles. Experiments with ferritin‐labelled antibodies to B. melaninogenicus LPS suggested a superficial location of LPS in the bacterial cells, but no further details.