Description of Chromobacterium
Purple pigmented bacteria, color coming from violacein, contains two subsets which may not be closely related: a fermentative and mesophilic one (growth at 37 degrees C but not at 4 degrees C), and a nonfermentative and psychrophilic one (growth at 4 degrees C but not at 37 degrees C). Gram-negative, oxidase-positive, catalase-positive rods with rounded ends which are usually motile by both a single polar flagellum and by one to four lateral flagella. Chromobacteria are facultative anaerobes and produce violet colonies on solid media; a violet ring is formed in liquid media at the surface with a fragile pellicle. Growth is best at 30 to 35 degrees C; the minimum growth temperature is 10 to 15 degrees C and the maximum is 40 degrees C (20% of the strains can grow at 44 degrees C). They are chemoorganotrophs using mainly carbohydrates fermentatively. Nitrate and usually nitrite are reduced, mostly with a variable gas production. They grow on ordinary media and are resistant to benzylpenicillin (10 ìg/ml) and to vibriostatic agent 0/129 [2,4-diamino-6,7-diisopropylpteridine (30 ìg/disc)]. The GC content of the DNA is 65 to 68 mol%.
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