![]() ![]() coli will consume glucose before lactose 1, 4, 5. ![]() The classic example involves the growth of the bacterium Escherichia coli on glucose and lactose, where E. This mechanism maximizes the growth rate by ensuring that cells devote their limited metabolic resources towards the preferred sugars 2. They do this by repressing the expression of the genes involved in metabolizing the less preferred sugars 2. Usually, the cells first consume the sugar yielding the highest growth rate, followed by the sugar yielding the next highest growth rate, and so on 3. Collectively, the results further our understanding of metabolism during growth on multiple sugars.ĭuring growth on a mixture of sugars, bacteria will often consume the sugars sequentially through a process known as catabolite repression 1, 2. In addition, we found that repression is reciprocal, where both L-arabinose and D-xylose also repress the lactose gene expression, albeit to a lesser extent and also through a mechanism involving cAMP. ![]() Our results demonstrate that it is due to cAMP and not transcriptional crosstalk. We investigated whether lactose-induced repression of L-arabinose and D-xylose gene expression is due to transcriptional crosstalk or cAMP. However, others have proposed that cAMP governs the hierarchical regulation of many non-glucose sugars. Previously, the preferential utilization of L-arabinose over D-xylose was found to result from transcriptional crosstalk. The metabolism of these sugars is regulated in a hierarchical manner, where lactose is the preferred sugar, followed by L-arabinose, and then D-xylose. In this work, we investigated the mechanism of catabolite repression in the bacterium Escherichia coli during growth on lactose, L-arabinose, and D-xylose. However, less is known about the mechanism for catabolite repression by these non-glucose sugars. ![]() While glucose provides the canonical example, many other sugars are also known to induce catabolite repression. Catabolite repression refers to the process where the metabolism of one sugar represses the genes involved in metabolizing another sugar. ![]()
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