Modulation of bacterial association to HeLa cell cultures by cell density and by chlamydial infection

Abstract

The effect of cell density on the rate of association of Escherichia coli and Staphylococcus aureus by monolayer cultures of HeLa 229 cells was investigated. Radioactively labeled bacteria were incubated with sparsely and densely plated cells. The rate of bacterial uptake was 10- to 20-fold higher in sparse cultures. Kinetic analysis of data with different multiplicities of input bacterial showed that the K of the reaction was unaltered, whereas the V was inversely related to cell density. pretreatment of HeLa cultures with dibutyryl adenosine 3',5'-phosphate had litle effect on the rate of bacterial association. The simultaneous presence of an obligately parasitic bacterium, Chlamydia trachomatis LGV434, enhanced the V of association of E. coli and S. aureus. This effect was more pronounced in dense HeLa cell cultures. Heat-inactivatd chlamydiae were unable to modify the association. Enhanced association persisted for at least 3 h after infection with chlamydiae.