Workshop 2 Description:

Workshop 2: Pattern formation and development in colonial organisms
Organizer: Philip Maini and Hans Othmer

E. coli and Dictyostelium are two of the most widely studied organisms in this area, so this workshop will focus in the main on these, but it is important that it is not restricted to these two examples. Research in this area falls naturally into the two broad categories of
(a) single cell,
(b) population level dynamics. We consider each in more detail below:

(a) At the single cell level, there are a number of phenomena that have been studied to various degrees of depth but for which explanations remain elusive. For example, a full understanding of signal transduction, namely, how do bacteria convert external stimuli into internal dynamics in a robust, yet incredibly sensitive manner (responding to a change in a few molecules over a background range of several orders of magnitude of molecules)? Within this, the goal is to understand gain and amplification. One possible explanation is receptor clustering but recent research suggests that this is not sufficient in itself. There are several alternative models for many of these processes but none are consistent with all the key known experimental behaviours.

Once the signal is internalised, the next question is to elucidate the cascade of reactions that determines response. For example, in E Coli, this triggers the flagellar motor to respond. One then has to understand the mechanism of motor operation and behaviour.

(b) At the cell population level it is known that within the laboratory bacteria can produce complex spatiotemporal patterns. Although this may be viewed as an interesting curiosity, it is felt that it will give important insights into the formation of biofilms which do have significant implications.

Other population level activity includes quorum sensing, differentiation etc. Complex patterns arise in myxobacteria, while in Dictyostelium discoideum (Dd) a range of morphogenetic behaviour is observed that is most likely conserved across species yielding important information for higher organisms. Dd is a powerful modelling paradigm for signal transduction, cell-cell signalling, cell differentiation, cell movement.

The implications of the above behaviours are widespread. For example, bacterial oral infections can lead to vascular disease, while biofilm formation is a major concern for the welfare of patients with surgical implants.

The mathematical disciplines used in the analysis of the models to be discussed in the workshop includes ordinary and partial differential equations, and stochastic equations.