Human gut bacteria tailor extracellular vesicle cargo for the breakdown of diet- and host-derived glycans

Extracellular vesicles are produced in all three domains of life, and their biogenesis has common ancient origins in eukaryotes and archaea. Although bacterial vesicles were discovered several decades ago and multiple roles have been attributed to them, no mechanism has been established for vesicles biogenesis in bacteria. For this reason, there is a significant level of skepticism about the biological relevance of bacterial vesicles. Bacteroides thetaiotaomicron (Bt), a prominent member of the human intestinal microbiota, produces significant amounts of outer membrane vesicles (OMVs) which have been proposed to play key physiological roles. Researchers at the Washington University School of Medicine employed a dual marker system, consisting of outer membrane- and OMV-specific markers fused to fluorescent proteins to visualize OMV biogenesis by time-lapse microscopy. Furthermore, they performed comparative proteomic analyses to show that, in Bt, the OMV cargo is adapted for the optimal utilization of different polysaccharides. The researchers also show that a negatively charged N-terminal motif acts as a signal for protein sorting into OMVs irrespective of the nutrient availability. These results demonstrate that OMV production is the result of a highly regulated process in Bt.

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Live OMV formation in Bt co-expressing Inulinase-GFP and OmpF-mCherry

Sartorio MG, Pardue EJ, Scott NE, Feldman MF. (2023) Human gut bacteria tailor extracellular vesicle cargo for the breakdown of diet- and host-derived glycans. PNAS 120(27):e2306314120. [article]

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