Shewanella species are a group of facultative Gram-negative microorganisms with remarkable respiration abilities that allow the use of a diverse array of terminal electron acceptors (EA). Like most bacteria, S. oneidensis possesses multiple terminal oxidases, including two heme-copper oxidases (caa 3 -and cbb 3 -type) and a bd-type quinol oxidase. As aerobic respiration is energetically favored, mechanisms underlying the fact that these microorganisms thrive in redox-stratified environments remain vastly unexplored. In this work, we discovered that the cbb 3 -type oxidase is the predominant system for respiration of oxygen (O 2 ), especially when O 2 is abundant. Under microaerobic conditions, the bd-type quinol oxidase has a significant role in addition to the cbb 3 -type oxidase. In contrast, multiple lines of evidence suggest that under test conditions the caa 3 -type oxidase, an analog to the mitochondrial enzyme, has no physiological significance, likely because of its extremely low expression. In addition, expression of both cbb 3 -and bd-type oxidases is under direct control of Crp (cAMP receptor protein) but not the well-established redox regulator Fnr (fumarate nitrate regulator) of canonical systems typified in Escherichia coli. These data, collectively, suggest that adaptation of S. oneidensis to redox-stratified environments is likely due to functional loss of the caa 3 -type oxidase and switch of the regulatory system for respiration.