Figure 7

Proposed mechanisms and functions of glycogen metabolic pathway in L. acidophilus . Based on proposed central functions of glycogen metabolism in other microorganisms [6],[11],[12] and findings from this study, carbohydrate substrates imported by the cells may be either metabolized through the glycolytic pathway, or shunted to glycogen biosynthetic pathway when a carbon source is not immediately required for glycolysis. The carbon pool may serve as an energy storage reserve and as a carbon capacitor that senses and modulates downstream carbon flow to maintain efficient carbon utilization and energetic homeostasis of the cells. The roles of glycogen metabolism in central carbon metabolism influence various physiological functions and consequently the retention and probiotic attributes of L. acidophilus. Our fundamental understanding of this pathway will inspire strategies to improve the stability and functionalities of probiotic and beneficial commensal microorganisms in the host.