The Biological Roles Of The Internalin-like Protein Lmo0549 In Flagellar-based Motility And Environmental Resistance Of Listeria Monocytogenes

Listeria monocytogenes is a Gram-positive intracellular parasite that can cause foodborne disease and high mortality in people and animals.The key to the pathogenesis of Listeria monocytogenes is its ability to internalize and proliferate in non-phagocytic cells.A family of proteins rich in leucine repeat region(LRR)and containing signal peptides at the N-terminal called internalin,which play an important role in Listeria monocytogenes infection.There are 25 kinds of proteins were considered as internalin,but the function of most of the internalins has not been clearly explained.Therefore,this study focused on the internalin family proteins Lmo1136,Lmo1289,Lmo2027,and Lmo0549,explored the biology functions of Lmo1136,Lmo1289,Lmo2027,and Lmo0549 in vitro and in vivo.1.Function of protein of internalin family Listeria monocytogenes in vitro growthListeria monocytogenes internalin Lmo1136,Lmo1289,Lmo2027,and Lmo0549 have no significant effect on the growth ability in vitro,but Lmo0549 was found to have significant effect on the motility and flagella synthesis of bacteria.Furthermore,it was found that the protein expression level of Fla A was significantly lower,however,the expression level of Gma R was enhanced.We here demonstrate that Listeria monocytogenes Lmo0549 has a strong effect on the flagellar-based motility2.The role of Lmo0549 on the infective ability of Listeria monocytogenesIn vitro cell test showed that the deletion of Listeria monocytogenes lmo0549 had no significant effect on the invasion and proliferation ability in cells.However,Lmo0549 can significant affect the migration ability of bacteria in fibroblast L929,and animal experiments showed that mutant strain pathogenicity of the mice was reduced.We here demonstrate that Listeria monocytogenes Lmo0549 reduce bacteria migration ability and pathogenicity.3.The role of Lmo0549 on gene expression of Listeria monocytogenesTranscriptomics result showed that sig B,inl B and plc B and phosphatase B shift enzyme system(PTS)transcription level were found to have significant difference after deletion of lmo0549.In order to verify the change of protein expression level,we collected the whole bacterial protein for Western Blot detection,the results showed that Sig B expression was increased.These results correspond to the results of transcriptomics.Moreover,The ability of listeria monocytogenes to resist salt and acid stress was enhanced.To sum up,the main proteins in this study,including Lmo1136,Lmo1289,Lmo2027,and Lmo0549,maybe not play a key role in the process of in vitro growth and in vivo infection.However,lmo0549 plays an important role in the motility and anti-stress ability of Listeria monocytogenes.The results of this study provide a basic study for further exploring the regulatory mechanism of Listeria monocytogenes in adapting to the environment and the mechanism of infection,and provide an important reference for the prevention and control of Listeria monocytogenes in subsequent studies.