A Novel LysR Family Factor STM0859 is Associated with The Responses of SalmonellaTyphimurium to Environmental Stress and Biofilm Formation

Salmonella entericasubsp. entericaserovar Typhimurium (ST) is an intracellularly parasitic bacterium. This zoonotic pathogen causes food poisoning and thus imposes a severe threat to food safety. Here, to understand the regulatory roles of the novel transcription factor STM0859 on the response of ST to environmental stress and biofilm formation, the STM0859gene-deficient strain and the complementation strain ?STM0859/STM0859were generated, respectively. Then, its capacity of responding to environmental stresses and biofilm (BF) formation ability under different stresses, including acid, alkali, high salt, cholate, and oxidative stresses was tested. We further analyzed the interaction between the STM0859 protein and the promoter of the acid stress response-related gene rcsBby performing an electrophoresis mobility shift assay (EMSA). The results showed that acid resistance and BF formation capacities of ST-?STM0859strain were significantly weaker, as compared with those of SalmonellaTyphimurium SL1344 (ST-SL1344) wild strain (p< 0.01). Quantitative qRT-PCR analysis showed that the expression levels of acid stress and BF formation-related genes, rcsBand rpoS, of ST-?STM0859strain were significantly reduced at the transcription levels, while the transcription levels of these genes were fully restored in complementation strain ST-?STM0859/STM0859. The results of EMSA showed that STM0859 was capable of binding the promoter DNA fragments of the rcsBgene, suggesting that STM0859 can promote the transcription of the rcsBgene through interaction with its promoter, thereby exerting an indirectly regulatory role on the adaptive responses to acid stress and BF formation of ST. This study provided new insights into the regulatory mechanisms of the LysR family factors on the tolerances of ST under adverse environmental stresses.