MEASUREMENT OF ELECTRICAL BIOIMPEDANCE FOR STUDYING UTILIZATION OF AMINO-ACIDS AND PEPTIDES BY PORPHYROMONAS-GINGIVALIS, FUSOBACTERIUM-NUCLEATUM, AND TREPONEMA-DENTICOLA

The growth response of Porphyromonas gingivalis, Fusobacterium nucleat um, and Treponema denticola to peptides (supplied as trypticase) and a mino acids (supplied as casamino acids) was measured over 24 hours by monitoring changes in alternating-current conductivity at 37-degrees-C . All species utilized peptides preferentially over amino acids. These results are consistent with those obtained previously with convention al growth-response experiments. The duration of the linear growth resp onse to trypticase of P. gingivalis was 9.7 hours, whereas that of bot h F. nucleatum and T. denticola was >24 hours. By contrast, there was more uniformity in the utilization of amino acids from the casamino ac id mixture, which previously has been shown to be a poor growth substr ate. Furthermore, subtle differences in growth patterns, such as the a bility of F. nucleatum to metabolize its storage glycopolymers before utilizing amino acids, were clearly evident. The present method provid es an excellent means of studying bacterial growth kinetics and deline ating bacterial/substrate specificities of both synthetic and natural substrates.