The fractal nature of biological aggregates

Abstract

This project demonstrates that biological aggregates are fractal. Zoogloea ramigera and Sacharomyces cerevisiae aggregates were grown in pure cultures, isolated, sized, and dispersed into single cells. Aggregate surface area, length, cells per floc, and porosity were determined and used to calculate fractal dimensions from four power law relationships. A fractal dimension of 1.94 ± .18 was calculated for Z. ramigera aggregates cultured in test tubes. This value is significantly less than the Euclidean value of 3, and indicates that these aggregates are highly fractal. S. cerevisiae aggregates cultured in test tubes had a fractal dimension of 2.86 ± .33 indicating that these aggregates are less fractal and more compact than Z. ramigera aggregates cultured under identical conditions. Z. ramigera aggregates cultured in a mixed Virtis reactor had a fractal dimension of 2.87 ± .29 indicating that the fractal nature of these aggregates is a function of the fluid environment.