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 sugges ted that dental plaque formation involved both interspecies binding be tween planktonic microorganisms ('coaggregation') as well as between p lanktonic and sessile microorganisms ('co-adhesion') and that co-adhes ion could be measured by analyzing the spatial arrangements of co-adhe ring microorganisms in a stationary end point state. Limited informati on is available, however, on the kinetics of coaggregation and co-adhe sion. The aim of this work was to develop a quantitative method to stu dy the kinetics of co-adhesion and to determine the effects of mass tr ansport conditions, like shear and concentration, on the kinetics of c o-adhesion. The kinetics of co-adhesion of the coaggregating and non-c oaggregating streptococci (S. oralis J22 and S. sanguis PK1889) to gla ss with adhering A. naeslundii T14V-J1 cells, have been studied in a p arallel plate flow chamber using real time image analysis. Initial loc al deposition rates in the vicinity of the Actinomyces were similar as observed on other regions over the substratum surface ('non-local dep osition rates') for the non-co-adhering pair, but were up to 19 times higher for the co-adhering pair. Thus, whereas we have previously show n that co-adhesion in a stationary end point state can be quantified b y radial pair distribution functions, this paper demonstrates that the tendency of coaggregating strains to co-adhere is also reflected in t he kinetics of co-adhesion. Local deposition rates increased with incr easing streptococcal concentration for the coaggregating pair. However , if it is attempted to increase the local deposition rate by increasi ng 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 ra tes for the coaggregating pair could not be explained on the basis of convective-diffusional mass transport towards the substratum, but requ ired accounting for collisions between adhering actinomyces and strept ococci flowing parallel to the surface.