DEPENDENCY OF TREPONEMA MICRODENTIUM ON OTHER ORAL ORGANISMS FOR ISOBUTYRATE, POLYAMINES, AND A CONTROLLED OXIDATION-REDUCTION POTENTIAL.

Socransky, S. S. (Forsyth Dental Center, Boston, Mass.), W. J. Loesche, C. Hubersak, and J. B. Macdonald. Dependency of Treponema microdentium on other oral organisms for isobutyrate, polyamines, and a controlled oxidation-reduction potential. J. Bacteriol. 88:200-209. 1964.-Strains of Treponema microdentium can be cultivated on a variety of autoclaved commercially available media in the presence of other oral organisms. Organisms supporting growth in these circumstances include a facultative diphtheroid accompanied by either a strain of Fusobacterium or a motile gram-negative anaerobic rod. Culture filtrates and lysates of these "supporting organisms" failed to substitute for growing organisms. Measurement of the oxidation-reduction potential of the test system demonstrated that the spirochetes grew in a narrow range of Eh (optimum, -190 mv). The supporting organisms could be replaced by their filtrates when the Eh of the medium was poised in this range by a combination of reducing agents. Both filtrates contained a heat-labile factor required by the spirochete, which could be replaced by 5 mug/ml of cocarboxylase. Isobutyric acid, which could be detected in the fusiform filtrate, and putrescine which could be detected in the diphtheroid filtrate, replaced the spirochete's remaining filtrate requirement. Maximal growth occurred when any of the following were incorporated into the medium: 2 mug/ml of sodium isobutyrate; 250 mug/ml of putrescine dihydrochloride; 200 mug/ml of spermidine phosphosphate, or 150 mug/ml of spermine tetrahydrochloride.