Biological functions of terminal oxidase subunit QoxB in Listeria monocytogenes

Abstract:

[Objective] Listeria monocytogenes is an important zoonotic foodborne intracellular pathogen. Here, we aimed to explore the biological functions of cytochrome aa3 terminal oxidase subunit QoxB in L. monocytogenes during bacterial growth and infection. [Methods] We constructed a qoxB deletion mutant ΔqoxB based on the wild-type strain EGD-e via homologous recombination. The differences regarding bacterial growth and intracellular infection were analyzed between the wild-type and the mutant strains. In addition, changes in the transcription of flagella-associated genes induced by the deletion of qoxB were determined by real-time quantitative reverse-transcription PCR (qRT-PCR). [Results] The deletion of qoxB did not affect the bacterial growth ability in vitro. However, the motility of ΔqoxB was significantly decreased compared with that of EGD-e. After incubation at 30 ℃ for 24 h and 48 h, the diameter of motility halos of ΔqoxB decreased by 35.86% and 34.2%, respectively, compared with that of EGD-e. The expression abundance of 22 flagella-associated genes reduced significantly in ΔqoxB. Moreover, compared with EGD-e, ΔqoxB showed significantly reduced abilities of cell adhesion, invasion, proliferation, and intracellular spread. [Conclusion] We demonstrated for the first time that QoxB played a critical role in the motility and infection of L. monocytogenes. The findings lay an important basis for elucidating the role of cytochrome terminal oxidase in the pathogenesis of bacterial pathogens.