6533b7dbfe1ef96bd12708c3

RESEARCH PRODUCT

C4 ‐dicarboxylates and l ‐aspartate utilization by Escherichia coli K‐12 in the mouse intestine: l ‐aspartate as a major substrate for fumarate respiration and as a nitrogen source

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C4-dicarboxylates, such as fumarate, L-malate and L-aspartate represent substrates for anaerobic growth of Escherichia coli by fumarate respiration. Here, we determined whether C4-dicarboxylate metabolism as well as fumarate respiration contribute to colonization of the mammalian intestinal tract. Metabolite profiling revealed that the murine small intestine contained high and low levels of L-aspartate and L-malate, respectively, whereas fumarate was nearly absent. Under laboratory conditions, addition of C4-dicarboxylate at concentrations corresponding to the levels of the C4-dicarboxylates in the small intestine (2.6 mMol/kg dry weight) induced the dcuBp-lacZ reporter gene (67% of maximal) in a DcuS-DcuR-dependent manner. In addition to its role as a precursor for fumarate respiration, L-aspartate was able to supply all the nitrogen required for anaerobically growing E. coli. DcuS-DcuR-dependent genes were transcribed in the murine intestine and mutants with defective anaerobic C4-dicarboxylate metabolism (dcuSR, frdA, dcuB, dcuA, and aspA genes) were impaired for colonizing the murine gut. We conclude that L-aspartate plays an important role in providing fumarate for fumarate respiration and supplying nitrogen for E. coli in the mouse intestine. This article is protected by copyright. All rights reserved.