The deposition of Streptococcus sanguis NCTC 7868 from a flowing suspension

Measurements were made of the rates at which continuously cultured Streptococcus sanguis NCTC 7868 cells accumulated on the inside surfaces of narrow glass capillaries from suspensions of the bacteria flowing down the capillaries at different velocities. Initially, the rate of accumulation of bacteria on the clean walls of the capillary was rapid. The deposition rate decreased with time, however, resulting in a saturation coverage of the glass surface which was considerably less than a monolayer. Multilayer coverage of the tube surface by bacteria was only achieved when fresh nutrient was pumped over deposited cells. This was attributed to cell growth. Although theoretical considerations of the deposition of small particles on to the walls of a tube suggest that the initial deposition rate should increase with flow rate, this was not the case with cells grown at dilution rates of 0.2 and 0.5 h-1. It is suggested that this can be explained by a polymer bridging mechanism of attachment.