Individual-based Modelling of Non-motile Bacterial Colony Formation In Structured Foods: A Comparative Study

Microbial dynamics in structured food products differ from microbial dynamics in liquids. In structured products, microorganisms are immobilised and constrained to grow as colonies, as opposed to liquid, where bacteria grow planktonically, i.e., dispersed or free-living. Little information is available on the displacement mechanisms within colony formation of non-motile bacteria. Three displacement mechanisms can be found in literature, i.e., (i) a discrete cellular automaton (CA) mechanism, (ii) a moving boundary mechanism, and (iii) a shoving mechanism. All three mechanisms are implemented in an individual-based modelling (IbM) environment. Advantages and disadvantages of each approach with respect to the individualbased modelling approach are summarised. The discrete CA results in the least realistic colony formation, but has the advantage of great computational speed. Both the moving boundary and the shoving mechanism produce biologically realistic results, albeit at a different level of detail for the representation of the environment. Both are suitable for IbM implementation and the choice depends on the level of detail necessary to describe the microbial phenomena under study.