Characteristics of Gram Negative Anaerobes
Some anaerobes, such as Bacteroides, contain two enzymes that protect them from oxygen - superoxide dismutase and catalase, which detoxify oxygen into water (see below).
While phylogenically distinct from gram negative aerobic enteric organisms, the cell wall structure of Bacteroides is similar. However, while Bacteroides also contains a lipopolysaccharide (LPS), it is distinctly different and not toxic. The LPS of fusobacteria, on the other hand, is a potent endotoxin.
The principle disease associated with Bacteroides and other gram negative anaerobes is their ability to form abscesses - mostly in mixed (aerobes and anaerobes) infections. How Bacteroides, Prevotella, and other gram negative anaerobes cause abscesses is not well understood, but their role appears to be critical.