
Water Science & Technology Vol 43 No 6 pp 135135 © IWA Publishing 2001
Effect of EPS on biofilm structure and function as revealed by an
individual-based model of biofilm growth
J-U Kreft* and JW Wimpenny**
*
Cardiff School of Biosciences, Cardiff University, PO Box 915,
Cardiff CF10 3TL, Wales, UK e-mail: kreft@cardiff.ac.uk
**
Cardiff School of Biosciences, Cardiff University, PO Box 915,
Cardiff CF10 3TL, Wales, UK
ABSTRACT
We have simulated a nitrifying biofilm with one ammonia and one nitrite
oxidising species in order to elucidate the effect of various extracellular
polymeric substance (EPS) production scenarios on biofilm structure and
function. The individual-based model (IbM) BacSim simulates diffusion of
all substrates on a two-dimensional lattice. Each bacterium is individually
simulated as a sphere of given size in a continuous, three-dimensional space.
EPS production kinetics was described by a growth rate dependent and an
independent term (Luedeking-Piret equation). The structure of the biofilm
was dramatically influenced by EPS production or capsule formation. EPS
production decreased growth of producers and stimulated growth of
non-producers because of the energy cost involved. For the same reason,
EPS accumulation can fall as its rate of production increases. The
patchiness and roughness of the biofilm decreased and the porosity
increased due to EPS production. EPS density was maximal in the middle of the vertical profile. Introduction of binding forces between like cells
increased clustering.
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