Characterization of the dppA1A2BCDF genes encoding a putative ABC transporter in Actinobacillus pleuropneumoniae: Role in glutathione utilization, oxidative stress tolerance and virulence.

Abstract

Actinobacillus pleuropneumoniae is a Gram-negative bacterium belonging to the genus Pasteurella. Porcine pleuropneumonia, caused by A. pleuropneumoniae, is a major respiratory disease in pigs and results in significant economic losses to the global swine industry. Sulfur is an essential nutrient for all life forms, and glutathione (GSH) serves as an alternative sulfur source for the growth of A. pleuropneumoniae. This study investigated the role of a potential ABC transporter family member (dppA1A2BCDF) in sulfur utilization and the virulence of A. pleuropneumoniae strain WF83. Single-gene deletion mutants ΔdppA1 and ΔdppA2, double-gene deletion mutants ΔdppA1A2-1 and ΔdppA1A2-2, as well as trans-complementation strains CA1, CA2, and CA1A2, were generated and characterized. Our results indicated that ΔdppA1A2-1 exhibited reduced growth in chemically defined medium supplemented with GSH as the sole sulfur source and increased sensitivity to oxidative challenges. In contrast, ΔdppA1A2-2, which retains the 164 bp sequence between dppA1 and dppA2 displayed phenotypes similar to the wild type. Animal infection assay suggested that ΔdppA1A2-1, despite impaired GSH utilization and antioxidant capacity, was not attenuated in pigs. Taken together, these results suggest that dppA1A2BCDF is involved in GSH utilization, and GSH deprivation potentially leads to increased oxidative sensitivity but is not essential for the virulence of this pathogen. These findings provide further insight into the complex regulation of sulfur assimilation and its significance during A. pleuropneumoniae infection.