Diversity and Dynamics of Bacterial Communities in Freshwater Lakes

Freshwater lakes host phylogenetically diverse microbes that are playing significant roles in elemental cycling in these ecosystems. In this chapter we present an accessible overview of the present knowledge of lake bacteria, their diversity, metabolism, and dynamics. The resolution offered by state-of-the-art metagenomics and single cell genomics approaches now provide unprecedented insights into the metabolic capabilities of yet to be cultured lake bacteria. These insights show that adaptations in predominant lake bacteria to low nutrient concentrations has led to the development of an intertwined network of metabolic dependencies in the bacterioplankton where exploration of how this is reflected in their dynamics and realized biogeochemical functions are in progress. While lakes across the world represent heterogeneous ecosystems, charismatic lake bacteria are globally distributed, and their dynamics is structured via the influence of both resource availability (bottom-up controls) and food web interactions (top-down controls). A prospective challenge to be addressed in future studies would be to more directly link functional traits of lake bacteria with their distribution patterns and to disentangle the implication of food web interactions on these traits. Ultimately this combined information can be used to develop mechanistic, informative, and robust models of “ecosystem metabolism” that offer capabilities to forecast ecosystem change due to climate impacts.