Bacteria are the cornerstones of all ecosystems, but our understanding of the factors that
govern the temporal and spatial distribution of bacteria remains limited. Bacterial communities are
often treated as well-mixed, but it is clear that, in most environments, they occupy discrete habitat
patches that contain different abiotic conditions and different sets of interacting species. While there
have been many studies that have investigated spatial structure at micrometer scales (e.g. biofilms)
and at kilometre scales (e.g. biogeographic distributions), there are few studies that have
investigated the role of spatial heterogeneity at the meso-scale (mm to cm). The meso-scale may be
particularly important for understanding the assembly and dynamics of bacterial communities
because it is the scale at which most bacterial dispersal occurs. This thesis assesses how
environmental heterogeneity impacts the assembly of bacterial communities occupying discrete
habitat patches which are connected by dispersal within miniature landscapes. The results from
these experiments using bacterial ‘metacommunities’ indicate that factors associated with dispersal
(e.g. species arrival timing and geographic distance) produce local variation in population sizes
despite landscape-level conservation of community structure. Furthermore, the impact of
environmental heterogeneity on the evolution and distribution of bacteria depended on their
capacity to disperse around the landscape. We therefore propose that understanding the details of
bacterial community assembly requires further understanding of the interaction between dispersalbased
processes and environmental heterogeneity.