Isolation of a bile salt sulfatase-producing Clostridium strain from rat intestinal microflora

Bile acid sulfates, formed in human and rat livers, are desulfated by the intestinal microflora. In our study we first isolated from conventional rat feces an unnamed bacterium, termed strain S1, which desulfated the 5 beta-bile salt 3 alpha-sulfates in vitro and in vivo after association with gnotobiotic rats. Strain S1 also possessed 12 alpha-hydroxysteroid dehydrogenase and bile salt-deconjugating activities. The strain was a strict anaerobic, CO2-requiring, gram-negative, sporeforming rod and was designated as belonging to the genus Clostridium. Growth was scarce in culture media, unless in the presence of 0.1% taurine, a sulfur-containing amino acid. Addition of this substance raised the number of bacteria in thioglycolate and peptone yeast media from 10(4) per ml to 10(6) to 10(7) per ml and increased the colony diameter on agar medium from 0.2 mm to 0.5 to 0.9 mm. Sulfatase activity was specific for the 5 beta-bile salt sulfates, leaving the 5 alpha-bile salt sulfates unchanged. In addition, the sulfatase activity was cell bound, and its production was dependent on the composition of the culture medium, although no minimal sulfur medium was required for sulfatase activity.