Spatial constraints drive amylosome-mediated resistant starch degradation by Ruminococcus bromii in the human colon
The 2025 study, ‘Spatial constraints drive amylosome-mediated resistant starch degradation by Ruminococcus bromii in the human colon,’ investigated how the amylosome, a cell-bound enzyme complex, enables R. bromii to degrade resistant starch (RS), and the researchers employed bacterial cultures, not human participants. Cells were cultivated on various carbon sources and analyzed using cryo–electron tomography, quantitative proteomics, and enzyme assays to characterize the structure, composition, and activity of the amylosome.
The results demonstrated that the amylosome forms a dense protein layer anchored to the cell wall and extending toward RS granules. When R. bromii is grown on RS, the amylosome alters its composition, with the enzymes Amy4 and Amy16 comprising approximately 60% of the complex and providing complementary activity against amylose and amylopectin. These compositional changes provided insight into how R. bromii adapts to varying dietary substrates while maintaining efficient RS degradation.
These findings indicate that RS degradation relies on an amylosome that is structurally stable yet compositionally adaptable. The study underscores the influence of microbial architecture and regulatory mechanisms on fiber metabolism, although the results are derived from isolated cultures rather than complete gut communities. Future investigations should evaluate these mechanisms in more complex microbiome environments and assess how dietary factors or community composition influence amylosome function.
In summary, the study highlights the role of specialized microbial structures (amylosome) in the processing of dietary fiber by gut bacteria.
