New cultivation techniques and laboratory model systems for investigating the growth of stratified microbial communities

Algal mats are one example of a large range of microbial ecosystems which are spatially heterogeneous and dominated by physico-chemical gradients. Such gradients can be expressed over a huge range of physical dimensions. pH gradients at the nm level occur around clay crystal domains Bacterial colonies show oxygen gradients from fully saturated to anoxic over 20 to 30 µm whilst biofilms and algal mat communities range from tens of µm to mm in depth. Gradients over soil profiles are expressed in the cm range whilst stratified water bodies incorporate gradients that range from meters to hundreds of metres. As these examples indicate, probably the majority of microbial systems are spatially heterogeneous.