KINETICS AND STOICHIOMETRY OF GROWTH OF PSEUDOMONAS-FLUORESCENS AND ALCALIGENES SP ON AN AGAR-CONTAINING MEDIUM

Development of bacterial lawn on the surface of an agar-containing med ium was studied by monitoring variation of the total cell mass of micr oorganisms, the number of viable cells, the residual substrate in the agar layer, and the respiration rate (CO2 formation). The growth patte rns were basically similar for both cultures: with a relatively consta nt substrate replenishment by diffusion from the agar layer, the speci fic growth rate, mu, the rate of substrate utilization, q, and the bio mass yield, Y, exhibited a steady decline. In the first phase of biofi lm development, mu and Y were virtually equal to the corresponding gro wth parameters for a homogeneous batch culture. The growth of Alcalige nes sp. on solid medium was, however, more stable than that of Pseudom onas fluorescens and proceeded without accumulation of dead cells. Thi s can probably be explained by the ability of Alcaligenes sp. to form extracellular gas chanals, which supply oxygen into the deep layers of biofilm. A mathematical model is proposed that describes the mechanis m of bacterial film growth on the surface of an agar-containing medium .