The effects of tetradecyl-4-ethyl-pyridinium chloride on the maximum specific growth rate biomass and hydrolytic enzyme production of Bacteroides gingivalis in continuous culture.

Bacteroides gingivalis was grown in continuous culture in the presence of tetradecyl-4-ethyl-pyridinium chloride (TDEPC). The maximum specific growth rate and biomass levels decreased with increasing concentrations of antimicrobial and complete inhibition of growth occurred when the TDEPC concentration reached 40 mg/l. Hydrolytic enzymes were detected in cells, vesicles and supernatant fractions of whole culture. Levels of alkaline phosphatase initially increased with increasing concentrations of TDEPC, but at higher concentrations (15-20 mg/l) of antimicrobial decreased significantly to less than 20% of the control value. The levels of N-acetyl-beta-glucosaminidase remained approximately constant at lower concentrations of TDEPC (0 10 mg/l) but then decreased significantly at higher concentrations. In contrast, levels of trypsin-like protease were reduced significantly at even low concentrations of TDEPC (5 10 mg/l) and decreased further as the TDEPC concentration increased. Therefore, TDEPC exerts significant physiological effects on B. gingivalis at concentrations below those considered to be lethal to the cell.