Involvement of the <i>cbb</i>₃-Type Terminal Oxidase in Growth Competition of Bacteria, Biofilm Formation, and in Switching between Denitrification and Aerobic Respiration

• Main Authors: Igor Kučera, Vojtěch Sedláček
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Microorganisms
• Subjects: respiratory chain; terminal oxidases; denitrification; branched electron flow; biofilm
• Online Access: https://www.mdpi.com/2076-2607/8/8/1230

<i>Paracoccus denitrificans</i> has a branched electron transport chain with three terminal oxidases transferring electrons to molecular oxygen, namely <i>aa</i>₃-type and <i>cbb</i>₃-type cytochrome <i>c</i> oxidases and <i>ba</i>₃-type ubiquinol oxidase. In the present study, we focused on strains expressing only one of these enzymes. The competition experiments showed that possession of <i>cbb</i>₃-type oxidase confers significant fitness advantage during oxygen-limited growth and supports the biofilm lifestyle. The <i>aa</i>₃-type oxidase was shown to allow rapid aerobic growth at a high oxygen supply. Activity of the denitrification pathway that had been expressed in cells grown anaerobically with nitrate was fully inhibitable by oxygen only in wild-type and <i>cbb</i>₃ strains, while in strains <i>aa</i>₃ and <i>ba</i>₃ dinitrogen production from nitrate and oxygen consumption occurred simultaneously. Together, the results highlight the importance of the <i>cbb</i>₃-type oxidase for the denitrification phenotype and suggest a way of obtaining novel bacterial strains capable of aerobic denitrification.