A family of obligate anaerobic (microaerophilic species may occur), nonsporeforming bacteria (order Eubacteriales) containing Gram-negative rods which vary in size from minute, filterable forms to long, filamentous, branching forms; pronounced pleomorphism may occur. Motile and nonmotile species occur; motile cells are peritrichous. Body fluids are frequently required for growth. Most species ferment carbohydrates, often with the production of acid; gas may be produced in glucose or peptone media. These organisms occur primarily in the lower intestinal tracts and mucous membranes of warm-blooded animals. They may be pathogenic. The type genus is Bacteroides.
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Bac·te·roi·da·ce·ae .bak-tə-.rȯi-'dā-sē-.ē n pl a family of extremely varied gram-negative bacteria (order Eubacteriales) that usu. live in the alimentary canal or on mucous surfaces of warm-blooded animals and are sometimes associated with acute infective processes see BACTEROIDES
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Bac·te·roi·da·ceae (bak″tər-oi-daґse-e) a family of gram-negative, obligately anaerobic bacteria of the phylum Bacteroidetes, consisting of non–spore-forming rods, nonmotile or motile with peritrichous flagella. The organisms occur naturally in the body cavities of animals and have been isolated from infections. Organisms of medical interest are included in the genera Bacteroides and Parabacteroides.Medical dictionary. 2011.