The Role Of DNA Repair Mechanisms In Listeria Monocytogenes Stress Survival,Mutagenesis And Host Colonization

Listeria monocytogenes,also known as listeria,is a foodborne bacterial pathogen that causes listeriosis,which can seriously lead to sepsis,meningitis,encephalitis,and abortion.Without effective treatment,it can cause serious complications or death.In addition,listeria is very prone to contaminating food and food-related industries.In China and abroad,there are frequent outbreaks of collective listeriosis due to listeria food contamination,which brings great trouble to our health,food processing industry and health safety.When listeria is exposed to external environmental pressure or internal pressure of itself,bacterial DNA damage will be caused.At this time,DNA repair pathways can effectively repair their DNA damage,which may be an important reason why listeria is resistant to high salt and lives in a wide range of p H and temperature and brings troubles to the food industry.Base excision repair?BER?,consisting mostly of lesion-specific DNA glycosylases and apurinic/apyrimidinic?AP?endonucleases,is one of the most important DNA repair mechanisms for repair of single nucleobase lesions generated by reactive oxygen and nitrogen species as part of an immune response against bacterial infections.However,few studies have addressed the contribution of BER to bacterial virulence and Listeria monocytogenes BER has thus far remained completely uncharacterized.In this study,by Markerless in-frame deleting 7 DNA glycosylase and 2 AP endonuclease in BER and deleting other important genes in another 3 pathways,19listeria mutant strains were constructed.Mainly use with hydrogen peroxide?H₂O₂?,Ethyl methyl sulfonate?MMS?and Spermine NONOate such as oxidation,alkylation and deamination reagent treatment,genes and mutants were tested for DNA damage survival,mutagenesis in the in vitro and the ability to colonize a mouse model of infection.Results show that identification of L.monocytogenes DNA glycosylases and AP endonucleases,It appears to contain multiple DNA glycosylases and AP endonucleases that are putatively involved in DNA repair as part of the BER pathway;Contribution of L.monocytogenes BER genes to DNA damage survival and repair;With MMS processing except?tag all mutants'mutation rate enhancement,?tag is very sensitive to MMS,?tag can't repair the alkylated base damage caused by MMS;it appears that activity of some of the DNA glycosylases and AP endonucleases could affect intracellular growth;The?mut Y,?nth and?ruv A mutants showed significant reduced CFU counts in the liver and spleen compared with the wild-type strain,the wild-type strain vastly outcompeted the?nth,?mut Y and?nfo deletion mutant for mouse colonization,indicating that some of the L.monocytogenes DNA glycosylases and AP endonucleases are important for survival of the DNA insults encountered in the host.In addition,the bactericidal experiment of ciprofloxacin and MMS showed DNA replication forks stalling of?ruv A mutant strain can cause massive death of bacteria.The spontaneous mutation rate of rifampicin showed that the substrates of Mut S had a high mutagenesis tendency.These results provided a comprehensive overview of the phenotypes associated with the L.monocytogenes BER pathway DNA glycosylases and AP endonucleases.It provides a theoretical basis for further understanding of listeria DNA repair.The survival characteristics of listeria under pressure also provide a theoretical basis for the prevention of contamination in the food industry.