Effects of ammonia and volatile fatty acids produced by oral bacteria on tissue culture cells

Abstract

Culture filtrates of several bacterial species isolated from the oral cavity were tested for their effects on two types of tissue culture cells: Vero cells, the continuous cell line of African green monkey kidney cells; and chondrocytes, isolated from 15-day-old chick embryo tibiae. Only a limited number of bacterial species--i.e., the asaccharolytic black-pigmented Bacteroides species and Fusobacterium species--affected the two cell types. The effect on Vero cells, detected by the rounding of the cells, correlated with the butyric acid concentration in the bacterial supernatant, which confirms previous findings. A small enhancement of this effect was found with propionic acid and ammonium ions. The same strains which affected Vero cells also affected chondrocytes, detected by a vacuolization of the cells. However, volatile fatty acids on their own had no visible effect on these cells. Instead, ammonium ion in the culture filtrate, when present in concentrations of 20 to 60 mmol/L, proved to be responsible for vacuolization of the chondrocytes. The volatile fatty acids (butyric and propionic) had a limited additive effect. No effects were visible with cell extracts of the bacteria.