The gut microbiota is made up of thousands of organisms that interact with available nutrients via outer-membrane proteins (OMPs). Here, we use single-molecule super-resolution microscopy to measure and understand these interactions. Specifically, the <i>Bacteroides thetaiotaomicron</i> (<i>Bt</i>) starch utilization system (Sus) is a prototype for glycan uptake by the bacteria, and Sus includes five OMPs which bind and transport starch. Although the molecular mechanisms of this system are well known, the dynamics and cooperativity of the Sus OMPs are still not fully understood. Based on new super-resolution fluorescence microscopy methods to locate, track, and analyze single molecules in living anaerobes, we have shown that the SusG enzyme explores the cell surface but slows upon interaction with starch. Furthermore, we have seen that the SusE and SusF OMPs are immobile on the cell surface even when other members of the system are knocked out and under multiple different growth conditions. These measurements suggest a new paradigm for protein complex formation: binding proteins form immobile complexes that transiently associate with a mobile enzyme partner. Thus, we are now completing the paradigm for glycan uptake by measuring and understanding the real-time interactions essential for carbohydrate catabolism in the human gut microbiome, with extensions to determining the response of three different carbohydrate utilization systems in diverse carbohydrate environments. Overall, our results provide fundamental insight of relevance to human health and disease.

Single-molecule imaging of cells detecting nutrients in their local environment

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.