Bursts of sectors in expanding bacterial colonies as a possible model for tumor growth and metastases

All kinds of hypotheses have been proposed to explain the mechanism of tumorigenesis. Up until now, we have not had any generally acknowledged model that helps us understand the process. However, it is well accepted that cancer development and progression is dictated by a series of alterations in genes such as oncogenes, tumor suppressor genes, DNA replication genes and others. Segregation of cell populations is a key question in evolution theory. One important aspect when observing cell proliferation in general or bacterial colonies in particular is the relation between spatial organization and the composition of the populations. Here we study a specific example—sectors in expanding bacterial colonies. Such sectors are spatially segregated sub-populations of mutants. Bursts of sectors are observed during compact growth and during branching growth. For theoretical studies of these bursts we employ two mathematical models. Using these models we investigate the amount of segregation achieved by a neutral mutation, as well as by mutations having some advantage over the wild type.