However, from a biological perspective the questions are, ‘What is the function of the apparent heterogeneity?’

and ‘What are the molecular mechanisms underlying the development of such heterogeneity?’. Understanding spatial heterogeneity provides one of the most striking successes in modeling that originated in discrete or hybrid mathematical models and was shortly thereafter demonstrated in a variety of continuum models (Dockery & Klapper, 2002; Cogan & Keener, 2004a, b). Analysis of these models indicated that spatial heterogeneity could be induced merely by competition for nutrients. In fact, in a variety of models (both discrete and continuous) spatial heterogeneity could be induced with no other processes included – even though it is clear that fluid forces and genetic expression

CTLA-4 antibody have an effect on structure. This turns the question around from, ‘What can cause spatial heterogeneity?’ to ‘How do the other factors, such as fluid forces, affect the physical heterogeneity?’. Other hypotheses have been proposed for the function and cause of spatial heterogeneity. It has been suggested that the presence of channels and towers, common structural elements of microbial biofilms, allows for increased nutrient VE-822 purchase access and uptake, which accords with the above theoretical explanation; however, other reasoning argues that structures form through interactions with the external fluid motion (Cogan & Keener, 2004a, b). At least one model has indicated that fluid/biofilm interaction can induce channels even in the absence of growth (Cogan & Keener, 2004a, b). The apparent spatial structures could also serve the function of reducing the material stress within the biofilm

via detachment or spatial organization. Other physical models have attempted to address the redistribution of biomass produced by the developing biofilm (Eberl & van Loosdrecht, 2001; Dockery & Klapper, 2002). Analysis of these models suggests that the interplay between various species and the environment Cell Penetrating Peptide may lead to physical and phenotypic heterogeneity. Others have tried to quantify the material properties of the biofilm itself (Klapper et al., 2002). Still others have attempted to determine how the material structure of the biofilm affects the spatial development (Eberl & van Loosdrecht, 2001; Cogan & Keener, 2004a, b; Alpkvist & Klapper, 2007). Each of these models begins with simplification of the biology and then tries to explain the apparent behavior in light of the remaining processes. While this approach may neglect important influences, the goal is to strip the problem down to some essential characteristics that are specific and hopefully quantifiable.