Clostridium orbiscindens sp. nov., a human intestinal bacterium capable of cleaving the flavonoid C-ring.

Clostridium orbiscindens sp. nov. is an obligate anaerobe that is capable of cleaving the C-3-C-4 bond of the natural anticarcinogen quercetin. The metabolic products, 3,4-dihydroxyphenylacetic acid and presumably phlorglucinol, are not known to possess anticarcinogen properties. This organism was isolated from human feces. On sheep blood agar plates C. orbiscindens forms minute, irregular, convex, gray or white, shiny, smooth, nonhemolytic colonies. It is beta-hemolytic on rabbit blood agar. The motile peritrichous rods are gram variable. Subpolar spores are common. Cultures are resistant to 80 degrees C for 10 min. Capsules are absent. This asaccharolytic organism does not metabolize esculin, urea, meat, gelatin, casein, or nitrate. The G + C content is 56 to 57 mol%. DNA hybridization experiments did not reveal relatedness to phenotypically similar Clostridium strains. Strain 265 (= ATCC 49531) is the type strain.