Definition: A genus of anaerobic, nonmotile bacteria containing gram-negative, straight or slightly curved rods, 5–15 mcm in length, with one or both ends rounded, often pointed. Granules are distributed evenly along the long axis, and one or more large granules may localize near the end of the cell. Branched or clubbed forms do not occur. Two or more cells join together and form septate filaments of varying length; in older cultures, filaments up to 200 mcm may form and twist around each other; large, coccoid bodies may be found within a filament as a cell lyses. Carbon dioxide is essential for optimal growth. Lactic acid is produced from glucose. These organisms occur in the oral cavity of humans. The type species is Leptotrichia buccalis.
[lepto- + G. thrix, hair]