FIG 5.

C₄-dicarboxylates as substrates or products of metabolism, and as signaling molecules for host/microbiota interaction in the intestine. Hexose fermentation, fumarate respiration (FR) and microaerobic respiration run in parallel under the microaerobic conditions of the intestine. The intestinal C4-DCs (black) serve as stimuli of the DcuS regulated metabolism of enteric bacteria, and of chemotaxis by Tar. Succinate produced by the enteric bacteria (red) or other microbiota is used for signaling or for communication with host cell, and succinate of host cells (macrophages) stimulates virulence and pathogenicity of S. Typhimurium. See the text for details. CytBD, microaerobic Cyt bd oxygen reductase; Fo, formate; ROS, reactive oxygen species; other abbreviations as in Fig. 1 to 4.