A family of nonmotile, nonsporeforming, anaerobic bacteria (order Eubacteriales) containing gram-negative (with a tendency to resist decolorization) cocci that vary in diameter from small (0.3–0.5 mcm) to large (2.5 mcm). Characteristically, they occur in pairs; single cells, masses, or chains may also occur, but the chains may show gaps illustrating the basic diplococcal arrangement. These organisms are chemoorganotrophic; they may or may not ferment carbohydrates; they are parasites of homothermic animals such as humans, ruminants, rodents, and pigs, and are primarily found in the alimentary tract. The type genus is Veillonella.
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