A gram-positive, rod-shaped bacterium, originally thought by Auger (1974) to be the agent of Pierce's disease of grapevines, is commonly associated with , one of the leafhopper vectors of the disease. The bacterium has the following colonial and cellular characteristics: smooth, glistening white, or chalky colonies, 0.4 to 0.5 mm in diameter with entire margins; gram positive becoming gram variable after 5 days in culture; nonmotile and nonsporeforming; grows between 15 and 37°C with an optimum between 28 and 30°C and no growth at 9 or 45°C; optimum growth occurs at pH 6.5, with growth observed at pH 4.5 and pH 9.0. The bacterium does not survive after 5 to 7 days of growth and must be maintained on fresh medium. It is rod-shaped (0.6 by 1.5 to 2.0 μm), growing in short chains of three to four cells each, and possesses mesosomes and a cell wall of uniform thickness (28 to 35 nm) that consists of an electrondense outer layer and an inner layer resembling unit-membrane structure. The organism is a facultative anaerobe which reacts negatively in tests for cytochrome oxidase, catalase, “gelatinase,” urease, tryptophanase, and nitrate and disulfide reductase activities. No dextran or levan is produced from sucrose. It produces L-(+)-lactic acid but not D-(—)-lactic acid from glucose and sucrose fermentation, acetylmethylcarbinol, or arginine deaminase. Glucose, sucrose, galactose, maltose, fructose, trehalose, salicin, inulin, and cellobiose, but not gluconate, lactose, mannose, mannitol, sorbitol, melibiose, or raffinose, were utilized as carbon sources. Its chromosome has an average guanine-plus-cytosine content of 32.75 mol%. Based on these features, the bacterium appears to be a hitherto unrecognized species of the genus , for which the name sp. nov. is proposed. The type strain is HC-1 (= ATCC 29071).


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