Abstract: This study aimed to explore the nuclease activity of extracellular products from Salmonella Choleraesuis and its effect on the formation of macrophages extracellular traps (METs). Agar culture assay, agarose gel electrophoresis, and agar diffusion method were used to investigate the nuclease activity of extracellular products of S. Choleraesuis. Effects of temperature, pH, and metal ions on the nuclease activity of extracellular products were explored by agarose gel electrophoresis. The effect of the extracellular products on METs induced by Candida albicans was measured. The results showed that λDNA was degraded by the extracellular products from S. Choleraesuis. The nuclease activity was inhibited under a high temperature and acidic conditions. The optimum temperature and pH of the nuclease activity were 42℃ and pH 9.0, respectively. The nuclease of the extracellular products was inactivated under a high temperature of 60℃ or higher. Na⁺, K⁺, Ca²⁺, and Ni²⁺ did not affect the nuclease activity. The high ionic strength of Ba²⁺, Mg²⁺, and Mn²⁺ with 5.00 and 10.00 mmol·L^-1 enhanced the nuclease activity of extracellular products. The activity of cleave λDNA promoted with the concentrations of 0.01-1.00 mmol·L^-1 of Zn²⁺, Cu²⁺, and Fe³⁺; conversely, low concentrations of 0.01-1.00 mmol·L^-1 of Co²⁺ inhibited the nuclease activity. Fluorescence microscope and quantification analyses revealed that the METs induced by Candida albicans were degraded by the extracellular products from S. Choleraesuis. This study confirmed that the extracellular products from S. Choleraesuis have nuclease activity, which provides a reference for further study of the role of extracellular products in the interaction between S. Choleraesuis infection and the host immune.

Key words: Salmonella Choleraesuis, extracellular products, nuclease, macrophages, extracellular traps