Quantitative proteomics reveals oxygen-induced adaptations in Caldalkalibacillus thermarum TA2.A1 microaerobic chemostat cultures

• Published in: Frontiers in microbiology 2024-10, Vol.15, p.1468929
• Main Authors: de Jong, Samuel I, Wissink, Martijn, Yildirim, Kadir, Pabst, Martin, van Loosdrecht, Mark C M, McMillan, Duncan G G
• Format: Article
• Language: English
• Subjects: adaptation; alkaliphile; chemostat; microaerobic; Microbiology; regulation; respiration
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2024.1468929

The thermoalkaliphile possesses a highly branched respiratory chain. These primarily facilitate growth at a wide range of dissolved oxygen levels. The aim of this study was to investigate the regulation of respiratory chain. was cultivated in chemostat bioreactors with a range of oxygen levels (0.25% O -4.2% O ). Proteomic analysis unexpectedly showed that both the type I and the type II NADH dehydrogenase present are constitutive. The two terminal oxidases detected were the cytochrome :oxygen oxidase, whose abundance was highest at 4.2% O . The cytochrome :oxygen oxidase was more abundant at most other O levels, but its abundance started to decline below 0.42% O . We expected this would result in the emergence of the cytochrome :oxygen complex or the menaquinol:oxygen complex, the other two terminal oxidases of ; but neither was detected. Furthermore, the sodium-proton antiporter complex Mrp was downregulated under the lower oxygen levels. Normally, in alkaliphiles, this enzyme is considered crucial for sodium homeostasis. We propose that the existence of a sodium:acetate exporter decreases the requirement for Mrp under strong oxygen limitation.