Aims Further investigations of the novel biological functions of SodA in Salmonella enterica serovar typhimurium (Salm. typhimurium). Methods and ResultsConclusionsA deletion mutant of sodA in Salm. typhimurium was constructed and its biological characteristics were analysed. More specifically, the roles of superoxide dismutase (SOD) in resistance to environmental stresses and serum, biofilm formation, epithelial cell adherence and invasion were investigated. Inactivation of sodA gene resulted in a slightly reduced growth rate, low SOD activity and increased susceptibility to reactive oxygen species and chicken serum. However, SodA was not involved in the motility of Salm. typhimurium. In addition, the sodA mutant exhibited a decreased capacity to form biofilm as well as to adhere and invade to HeLa cells, compared to the wild-type and complemented strains. Salmonella typhimurium SOD appears to play an important role in resistance to serum and oxidative stress, biofilm formation, adherence to and invasion of epithelial cells. Significance and Impact of the StudyThis study illustrates the novel roles of SodA in serum resistance and biofilm formation in Salm. typhimurium, which may provide a candidate for the biofilm eradication and prevention of infections.