class Bacteroidia is composed of a single order of environmental bacteria. By far, the Bacteroidales order are the most well-studied of the Bacteroidetes. Some members of the genus Bacteroides are opportunistic pathogens. Before the fourth volume of  came out, it was referred to as class Bacteroidetes. Bergey's Manual of Systematic Bacteriology 
References [ edit ]
^ Bergey's Manual of Systematic Bacteriology, 2nd ed., vol. 1 (The Archaea and the deeply branching and phototrophic Bacteria) (D.R. Boone and R.W. Castenholz, eds.), Springer-Verlag, New York (2001). pp. 465-466.
^ Krieg, N.R.; Ludwig, W.; Whitman, W.B.; Hedlund, B.P.; Paster, B.J.; Staley, J.T.; Ward, N.; Brown, D.; Parte, A. (November 24, 2010) [1984(Williams & Wilkins)]. George M. Garrity, ed. . Bergey's Manual of Systematic Bacteriology. The Bacteroidetes, Spirochaetes, Tenericutes (Mollicutes), Acidobacteria, Fibrobacteres, Fusobacteria, Dictyoglomi, Gemmatimonadetes, Lentisphaerae, Verrucomicrobia, Chlamydiae, and Planctomycetes 4 (2nd ed.). New York: Springer. p. 908. ISBN 978-0-387-95042-6. British Library no. GBA561951.