Protein complexes in marine bacteria may control the rate of glycan uptake and degradation, and thus the scale of carbon sequestration. We will elucidate how protein interactions and enzyme cascades help bacteria to cope with the extraordinary variability and complexity of algal glycans under specific marine environmental conditions. The project progresses from an examination of single protein functions to protein complexes. By investigating the structure and function of glycan-degrading protein machines, this project directly addresses the CONCENTRATE hypothesis of why some glycans resist degradation and contribute to carbon sequestration.