Bacteroidetes and Fusobacteria

The two phyla, Bacteroidetes plus Fusobacteria, are grouped in the same chapter here, because they were both formerly assigned to the same (now obsolete) class, Saprospirae, the gliding, fermenting bacteria. Fermentation is a metabolic process wherein organic molecules yield energy. Bacterial gliding is a process in which cells on a flat surface move through excreted slime (polysaccharides). The process of gliding is different from the process of swimming, and does not require flagella. Aside from organisms in Class Bacteroidetes and Class Fusobacteria (Chapter 10), and gliding was also seen in some members of Class Gamma proteobacteria (Chapter 7), particularly Class Pseudomonadales. Class Bacteroidetes has two major subdivisions, Class Bacteroidales and Class Flavobacteria. The two divisions lack morphologic resemblance and are physiologically distinct (Bacteroidales is anaerobic, Class Flavobacteria is aerobic). Nonetheless, their genotypes are similar, and some species from either group produce sphingolipids, a chemical that is seldom encountered in other eubacterial classes.