Genome evolution of the marine Roseobacter clade

Members of the Roseobacter clade represent up to 20% of the bacterial cells in coastal waters and 3-5% in open ocean waters. Although the clade members diverge by only 11% in their 16S rRNA gene sequences, they contain a substantial genetic diversity, which is consistent with their prevalence in all kinds of marine habitats. For instance, they are often dominant members in the bacterial communities associated with phytoplankton, macroalgae, and various marine animals. They are ubiquitous from tropical to polar oceans, the latter including sea ice habitats. They are also common members in the deep pelagic environments and marine sediments.

We are initiating the ten thousand Roseobacter genome sequencing project, with a major goal to capture the genomic diversity of cultured and uncultivated Roseobacters from the global oceans, including major habitats such as surface and dark pelagic environments, coastal and deep sea sediments, associated with phytoplankton and corals. We are investigating how selection, drift, mutation, and recombination act to assemble this diversity using phylogenomic and population genomic approaches.

Role of environmental factors in the evolution of marine bacteria & archaea

Ocean waters represent a landscape of physicochemical parameters. We are studying how various environmental factors (among others, oxygen, light, temperature, salinity, and nutrient availability) influence the genome content and nucleotide composition of ecologically relevant marine bacterial and archaeal lineages. The major approach is to collect and sequence evolutionary related lineages inhabiting divergent ecological context, followed by comparative genomic analyses. This may yield findings with predictive power showing microbial response in a changing ocean.