Ruminococcus bromii enables the growth of proximal Bacteroides thetaiotaomicron by releasing glucose during starch degradation

• Published in: Microbiology (Society for General Microbiology) 2022-04, Vol.168 (4)
• Main Authors: Rangarajan, Aathmaja Anandhi, Chia, Hannah E, Azaldegui, Christopher A, Olszewski, Monica H, Pereira, Gabriel V, Koropatkin, Nicole M, Biteen, Julie S
• Format: Article
• Language: English
• Subjects: Amylopectin; Bacteria - metabolism; Bacteroides thetaiotaomicron - metabolism; Glucose; Resistant Starch; Ruminococcus; Starch - metabolism
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.001180

Complex carbohydrates shape the gut microbiota, and the collective fermentation of resistant starch by gut microbes positively affects human health through enhanced butyrate production. The keystone species ( ) is a specialist in degrading resistant starch; its degradation products are used by other bacteria including ( ). We analysed the metabolic and spatial relationships between and during potato starch degradation and found that utilizes glucose that is released from upon degradation of resistant potato starch and soluble potato amylopectin. Additionally, we found that produces a halo of glucose around it when grown on solid media containing potato amylopectin and that cells deficient for growth on potato amylopectin (∆ ) can grow within the halo. Furthermore, when these ∆ cells grow within this glucose halo, they have an elongated cell morphology. This long-cell phenotype depends on the glucose concentration in the solid media: longer cells are formed at higher glucose concentrations. Together, our results indicate that starch degradation by cross-feeds other bacteria in the surrounding region by releasing glucose. Our results also elucidate the adaptive morphology of cells under different nutrient and physiological conditions.