Two distinct, membrane-bound, FAD-containing enzymes are responsible for the catalysis of fumarate and succinate interconversion; the fumarate reductase is used in anaerobic growth, and the succinate dehydrogenase is used in aerobic growth. a quinone + succinate = a quinol + fumarate Flavinylated by SdhE, flavinylation occurs at a very low level in the absence of SdhE. Carbohydrate metabolism; tricarboxylic acid cycle; fumarate from succinate (bacterial route): step 1/1. Makes weak or transient interactions with SdhA (PubMed:22474332, PubMed:24070374). Part of an enzyme complex containing four subunits: a flavoprotein, an iron-sulfur, cytochrome b-556, and a hydrophobic anchor protein. The complex forms trimers. No effect on anaerobic growth on glycerol fumarate medium. Belongs to the FAD-dependent oxidoreductase 2 family. FRD/SDH subfamily.