FIGURE 4.

Illustration and expression patterns of genes for ethanol and common respiratory chains, as well as genes coding for ATP synthetase. During oxidation of ethanol to acetic acid, both of the membranes bound PQQ-ADH and PQQ-ALDH transfer electrons to ubiquinone (Q), the reducing form (QH₂) of which is subsequently oxidized by terminal oxidase cytochrome O with pumping out the protons to generate proton motive force (PMF). PMF is then utilized by ATP synthetase for ATP generation. Therefore, PQQ-ADH and PQQ-ALDH form a typical ethanol respiratory chain in AAB, making AAB cells able to directly and rapidly utilize the energy released from incomplete oxidation of ethanol. The expression profiles of genes are placed right above (for ethanol respiratory chain, i.e., PQQ-ADH and PQQ-ALDH, in curves) or below (for common respiratory chain, i.e., NADH dehydrogenase and succinate dehydrogenase, and ATP synthetase, in heatmaps) the corresponding components. Detailed FPKM and Log₂ (fold change) values together with the annotation of each gene are listed in Supplementary Table S2.