[Growth and substrate utilization by bacterial lawn on the agar surface: experiment and one-dimensional distributed...

Cell mass dynamics of the lawns formed by Pseudomonas fluorescens and Alcaligenes sp. and the distribution profiles of the residual substrate in the agar layer were monitored. After one or two days of culturing, the concentration of pyruvate in the top agar layer adjacent to the lawn dropped below the level of detection, and, from this moment, the substrate was supplied to the lawn by diffusion from underlying agar layers. Diffusion of pyruvate in noninoculated bilayered agar was found to follow Fick's equation with the diffusion coefficient of 0.042 cm2/h. A distributed mathematical model adequately describing the growth of bacterial lawn was developed based on the diffusion equation and the Monod-Herbert kinetic model. Notable distinctions between the two cultures studied were revealed: pseudomonads had higher growth and death rates than Alcaligenes sp. and exhibited a greater affinity for the substrate.