Microbial communities – structure and dynamics
The most common approach to estimate microbial diversity is based on the analysis of DNA sequences of specific target genes including ribosomal genes. Analysis of such sequences have revealed an immense genetic diversity of microorganisms, most of which is not yet characterized. In this project, the structure and dynamics of communities of marine bacterioplankton are studied. Because of their small size, great abundance and easy dispersal, it is often assumed that these bacteria have a ubiquitous distribution that prevents any structured assembly into local communities. However, we have shown that marine bacterioplankton communities display distinct patterns of diversity and structure that include a clear latitudinal gradient of species richness, a high degree of endemism, and few cosmopolitan species. We are now conducting experimental studies on bacterial communities from the Baltic Sea and the North Sea, which allows detailed comparative studies of community dynamics and the phylogenetic contingencies of community structure. In this way, we can advance our understanding of how the current environmental condition together with evolutionary history shapes bacterial communities.
The most common approach to estimate microbial diversity based on the ribosomal genes is to cluster sequences into operational taxonomic units (OTUs) based on genetic distance (sequence similarity). This method may fail to adequately identify clusters of evolutionary related sequences and it provides no information on the phylogenetic structure of the community. We have developed an ease-of-use web application, RAMI, which clusters related nodes in a phylogenetic tree based on the patristic distance (genetic change)