A QUANTITATIVE METHOD TO STUDY CO-ADHESION OF MICROORGANISMS IN A PARALLEL-PLATE FLOW CHAMBER .2. ANALYSIS OF THE KINETICS OF CO-ADHESION

Recently (J. Microbiological Methods 20, 289-305, 1994), it was suggested that dental plaque formation involved both interspecies binding between planktonic microorganisms ('coaggregation') as well as between planktonic and sessile microorganisms ('co-adhesion') and that co-adhesion could be measured by analyzing the spatial arrangements of co-adhering microorganisms in a stationary end point state. Limited information is available, however, on the kinetics of coaggregation and co-adhesion. The aim of this work was to develop a quantitative method to study the kinetics of co-adhesion and to determine the effects of mass transport conditions, like shear and concentration, on the kinetics of co-adhesion. The kinetics of co-adhesion of the coaggregating and non-coaggregating streptococci (S. oralis J22 and S. sanguis PK1889) to glass with adhering A. naeslundii T14V-J1 cells, have been studied in a parallel plate flow chamber using real time image analysis. Initial local deposition rates in the vicinity of the Actinomyces were similar as observed on other regions over the substratum surface ('non-local deposition rates') for the non-co-adhering pair, but were up to 19 times higher for the co-adhering pair. Thus, whereas we have previously shown that co-adhesion in a stationary end point state can be quantified by radial pair distribution functions, this paper demonstrates that the tendency of coaggregating strains to co-adhere is also reflected in the kinetics of co-adhesion. Local deposition rates increased with increasing streptococcal concentration for the coaggregating pair. However, if it is attempted to increase the local deposition rate by increasing the shear, it was found that local deposition rates decreased, most likely because the interaction time between the adhering actinomyces and the flowing streptococci becomes too short. The high deposition rates for the coaggregating pair could not be explained on the basis of convective-diffusional mass transport towards the substratum, but required accounting for collisions between adhering actinomyces and streptococci flowing parallel to the surface.