title: Formation of urso- and ursodeoxy-cholic acids from primary bile acids by a Clostridium limosum soil isolate.
abstract: A gram-positive, rod-shaped anaerobe (isolate F-14) was isolated from soil. This organism was identified by cellular morphology as well as by fermentative and biochemical data as Clostridium limosum. Isolate F-14 formed ursocholic acid (UC) and 7-ketodeoxycholic acid (7-KDC) from cholic acid (CA), and ursodeoxycholic acid (UDC) and 7-ketolithocholic acid (7-KLC) from chenodeoxycholic acid (CDC) in whole cell cultures, but did not transform deoxycholic acid (DC). No hydrolysis or transformation occurred when either taurine- or glycine-conjugated bile acids were incubated with F-14. The type stain of Clostridium limosum (American Type Culture Collection 25620) did not transform bile acids. The structures of ursocholic, ursodeoxycholic, 7-ketodeoxycholic, and 7-ketolithocholic acids were verified by mass spectroscopy and by thin-layer chromatography using Komarowsky's spray reagent. The organism transformed cholic and chenodeoxycholic acids at concentrations of 20 mM and 1 mM, respectively; higher concentrations of bile acids inhibited growth. Optimal yields of ursocholic and ursodeoxycholic acids were obtained at 9-24 hr of incubation and depended upon the substrate used. Increasing yields of 7-ketodeoxycholic and 7-ketolithocholic acids, and decreasing yields of ursocholic and ursodeoxycholic acids were observed with longer periods of incubation. Culture pH changed with time and was characterized by a small initial drop (0.2-0.4 pH units) and a subsequent increase to a pH (8.1-8.2) that was above the starting pH (7.4).(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D001647:Bile Acids and Salts / Q000378:metabolism; D019826:Cholic Acid; D002793:Cholic Acids / Q000096:biosynthesis* / Q000378:metabolism*; D002855:Chromatography, Thin Layer; D003013:Clostridium / Q000378:metabolism*; D003840:Deoxycholic Acid / Q000031:analogs & derivatives*; D012988:Soil Microbiology; D013237:Stereoisomerism; D014580:Ursodeoxycholic Acid / Q000096:biosynthesis*
chemical_list: D001647:Bile Acids and Salts; D002793:Cholic Acids; D003840:Deoxycholic Acid; D014580:Ursodeoxycholic Acid; D019826:Cholic Acid; C030712:ursocholic acid