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 nucleatum, and Treponema denticola to peptides (supplied as trypticase) and amino acids (supplied as casamino acids) was measured over 24 hours by monitoring changes in alternating-current conductivity at 37 o C. All species utilized peptides preferentially over amino acids. These results are consistent with those obtained previously with conventional growth-response experiments. The duration of the linear growth response to trypticase of P. gingivalis was 9.7 hours, whereas that of both F. nycleatum and T. denticola was >24 hours. By contrast, there was more uniformity in the utilization of amino acids from the casamino acid mixture, which previously has been shown to be a poor growth substrate