The metabolism of cholesterol and certain hormonal steroids by Treponema denticola

The aim was to investigate whether reference cultures and fresh isolates of Treponema denticola are able to 5α-reduce and further metabolise testosterone, 4-androstenedione, progesterone, corticosterone, cortisol or cholesterol. Two reference and five freshly isolated cultures of T. denticola were incubated with either radiolabeled or unlabeled steroid substrates; in the first case products were identified by thin layer chromatography and in the latter by gas chromatography–mass spectroscopy. All the substrates were 5α-reduced. Both reference cultures and fresh isolates of T. denticola presented 3β- and 17β-hydroxy steroid dehydrogenase activity. It was concluded that T. denticola was capable of steroid metabolism and hypotheses are discussed regarding the in vivo function of this metabolism including, T. denticola utilising host supplied steroids as growth factors and T. denticola steroid metabolism acting as a virulence factor.