Cells of Bacillus subtilis adsorbed on an anion-exchange resin, Dowex 1 in chloride form, were incubated in a growth medium in a batch or a continuous-flow system. In either system, the ratio of the number of spores to that of total organisms in the supernatant or in the effluent of adsorbed culture and the ratio on the resin surface were larger than the ratio in free cell culture and it was concluded that the spore formation of B. subtilis was significantly promoted by adsorption on the resin. When adsorbed cells were cultivated in a continuous-flow of growth medium, resin surface was nearly saturated with vegetative cells and spores during incubation. In this system, the ratio of the number of spores to that of total organisms was larger in the effluent than on the resin surface, suggesting that the spores tended to detach from the resin surface more easily than the vegetative cells.
On the basis of these observations, a model for the growth and spore formation of B. subtilis on the resin surface was presented. Kinetic equations were formulated for the growth and spore formation of adsorbed cells and it was shown that the spore formation rate of adsorbed cells was larger than that of free cells.