The orphan response regulator DegU regulates host cell infection and high-temperature adaptation of Listeria monocytogenes

Abstract:

[Objective] Listeria monocytogenes is a fooD-borne bacterial pathogen that is widely distributed in the environment. This study aims to investigate the regulatory role of the orphan response regulator DegU in the infection and high-temperature adaptation of L. monocytogenes. [Methods] The regulatory roles of DegU in three strains including wilD-type EGD-e, ΔdegU, and CΔdegU of L. monocytogenes were studied. The infection models established with human epithelial cell line Caco-2, mouse RAW264.7 macrophages, and murine fibroblast L929, real time quantitative polymerase chain reaction (RT-qPCR), and electrophoretic mobility shift assay (EMSA) were employed to investigate the roles of DegU in the infection and high-temperature adaptation. [Results] Compared with wilD-type EGD-e, ΔdegU showed weakened abilities to adhere, invade, proliferate, and migrate between host cells. The RT-qPCR results revealed that the transcription levels of the multiple virulence factors were down-regulated while that of clpE was up-regulated in ΔdegU. However, the transcription level of clpE was down-regulated at 43 ℃. Moreover, EMSA demonstrated that DegU bound directly with the promoter of clpE. [Conclusion] DegU plays a vital role in adhesion, invasion, proliferation, and migration of L. monocytogenes. Additionally, DegU directly binds with the promoter and regulates the transcriptional level of clpE to adapt to the high-temperature environment. The findings provide a basis for probing into the infection and environmental adaptation mechanisms of L. monocytogenes.