Chemically defined and minimal media forBacteroides gingivalis

Abstract

A chemically defined medium (BGDM) has been developed specifically forBacteroides gingivalis. The medium contains 4 amino acids, 5 mineral salts, cysteine hydrochloride as a reducing agent, and the growth factors hemin and menadione. Eight strains ofB. gingivalis have been subcultured repeatedly in this medium with no apparent changes in colonial or cellular morphology. The metabolic end products of strains grown in this medium were reproducible and yielded patterns similar to those produced by cells cultured in complex media. The growth rates were about 50% slower than those of cells grown in a complex medium, and the growth rate constants ranged between 0.013 and 0.067 H⁻¹. When the defined medium was supplemented with protein hydrolysates such as trypticase, proteose peptone, bactocasitone, or yeast extract, at concentrations up to 1.0%, growth increased. No such growth increase was observed in the medium supplemented with casamino acids. Thus a minimal medium can be formulated by adding one of the growth-enhancing protein hydrolysates to the defined medium at varying concentrations depending upon the growth yield required.