Erythritol, a natural sugar abundant in fruits and fermenting foods, is about 65 percent as sweet as table sugar and has about 95 percent fewer calories. It is 'tooth friendly' and generally devoid of negative side effects as a human consumable product. Pathogenic Brucella strains that catabolize erythritol contain four closely spaced genes, all involved in erythritol metabolism. One of the four genes (eryD) encodes a product that represses the expression of the other three genes. Erythritol catabolism is stimulated by erythritol. Present a simple regulatory model to account for the regulation of erythritol catabolism in Brucella. Does this system appear to be under inducible or repressible control?

Key Concepts

Gene Regulation

Gene regulation refers to the mechanisms that control the expression of genes, determining when and how much of a gene product is made. In the context of erythritol catabolism in Brucella, the regulation involves specific genes that can either promote or inhibit the expression of other genes based on the presence of erythritol. Understanding this concept is crucial for analyzing how Brucella adapts its metabolic processes in response to environmental changes.

Inducible vs. Repressible Systems

Inducible systems are those where gene expression is activated in response to a specific molecule, while repressible systems are typically active until turned off by a repressor molecule. In the case of erythritol catabolism, the presence of erythritol stimulates the expression of genes involved in its metabolism, suggesting an inducible system. Recognizing the difference between these systems is essential for understanding how metabolic pathways are regulated.

Metabolic Pathways

Metabolic pathways are series of chemical reactions occurring within a cell, where the product of one reaction serves as the substrate for the next. In Brucella, the metabolic pathway for erythritol catabolism involves multiple genes that work together to break down erythritol. Understanding these pathways helps elucidate how organisms utilize different substrates for energy and growth, and how they regulate these processes in response to environmental cues.