Microevolution of a planktonic freshwater bacterium studied along a latitudinal gradient

The majority of animal and plant species naturally inhabiting Europe show pronounced biogeographic restrictions in their South-to-North distribution. For several species with broader geographic ranges adaptation of local populations to local climate conditions was demonstrated. In contrast only little is known about the geographic distribution of microbial taxa across Europe, however, it is commonly assumed that species of microorganisms possess large geographic distribution ranges, but it is unknown if local adaptation of populations to local climate conditions took place. In this project we will test if a bacterial species known to possess a South-to-North distribution ranging at least from the Mediterranean Area to subarctic Northern Scandinavia is structured in local populations adapted to different climate conditions. The studied bacterium represents a free-living species dwelling in the water column of lakes and ponds, and represents an abundant member of freshwater bacterioplankton. We will isolate strains affiliated with this species from lakes located along a 3000 km South-to-North latitudinal gradient across Europe. The isolated strains will be tested for differences in physiological and biochemical adaptations to temperature and UV radiation. The population structure of the taxon along the latitudinal gradient and gene flow along this gradient will be analyzed by genome- sequencing of selected strains and multilocus sequence typing of all strains. The established datasets will enable the reconstruction of microevolutionary processes in these bacteria, and will provide insights in the potential of these abundant freshwater bacteria to adapt to changing environmental conditions. Thus, the gained knowledge will enable us to better predict if and how free-living bacteria will adapt to rapid climatic changes caused by global warming. Furthermore, this research will broaden our understanding of microbial diversity and will provide new insights into the controversial topic of microbial biogeography.