Mapping microdiversity structure of deep water-adapted Chloroflexi across the Laurentian Great Lakes

A globally abundant and poorly understood deep-water inhabitant of pelagic freshwater systems is Anaerolineae lineage CL500-11, an uncultivated bacterium in the Chloroflexi phylum. Around the world, CL500-11 comprises 10-30% of the bacterial community in the hypolimnia of deep oxic lakes, including the Laurentian Great Lakes (LGL). Here we use metagenome-assembled genomes (MAGs) to quantify and map the microdiversity structure of CL500-11 across the physiochemically heterogeneous LGL. In contrast to abundant marine surface water taxa like SAR11 and Prochlorococcus, where distinctive ecotypes are thought to support numerical dominance across environments, our CL500-11 MAGs share >99.4% average nucleotide identity, representing an extremely low diversity population throughout the LGL system. The most divergent MAGs come from Lake Erie, which is unique in nutrient load, volume, residence time, and surrounding land use among the otherwise oligotrophic LGL. This work suggests limited CL500-11 subpopulation structure even across long distances and strong environmental gradients, and it indicates the potential for deep water habitats to host unique ecological and evolutionary strategies that remain underexplored.

Primary Presenter: Jessica Hart, University of Chicago (hartjl@uchicago.edu)

Authors:

Jessica Hart, University of Chicago  (hartjl@uchicago.edu)

María Hernández-Limón, University of Chicago  (mdhernandez@uchicago.edu)

Justin Podowski, University of Chicago  (jpodowski@anl.gov)

Maureen Coleman, University of Chicago  (mlcoleman@uchicago.edu)