Abstract
Actinobacillus pleuropneumoniae is the pathogen of porcine contagious pleuropneumonia. In A. pleuropneumoniae, the CpxAR two-component system is essential for fitness and growth. The O-antigen protrudes from the outer membrane to the exterior of the cell, and the outer membrane serves as a barrier that helps the bacteria to survive in harsh environments. WecA, a undecaprenyl phosphate GlcNAc-1-phosphate transferase, is involved in O-antigen repeating unit biosynthesis. In this study, we investigated the role of CpxAR in the expression of wecA in A. pleuropneumoniae. Our results revealed that CpxR positively regulates wecA expression by directly binding to the putative promoter region of wecA. Wild-type, ΔcpxAR, ΔwecA, and complemented strains were investigated under serum, oxidative, and osmotic stresses. The ΔcpxAR and ΔwecA strains were more susceptible to these stresses than the wild-type, but the complemented strains showed phenotypes similar to those of the wild-type. Mice infected with the ΔcpxAR and ΔwecA strains exhibited lower mortality and bacterial loads in the lung than those infected with the wild-type or complemented strains. This study reveals that the CpxAR two-component system contributes to A. pleuropneumoniae growth, stress resistance, and virulence, by upregulating expression of wecA. Our findings provide new insight into the pathogenesis of A. pleuropneumoniae.
Highlights
Porcine contagious pleuropneumonia is a highly contagious respiratory disease that causes considerable losses to the global swine industry (Sassu et al, 2018)
To investigate whether WecA is involved in stress resistance, the wild-type strain A. pleuropneumoniae 4074 was treated with serum, NaCl, and H2O2, respectively
In Gram-negative bacteria, the envelope has been reported to be essential for nutrient transport, adhesion, viability, stress resistance, and virulence (Bury-Mone et al, 2009)
Summary
Porcine contagious pleuropneumonia is a highly contagious respiratory disease that causes considerable losses to the global swine industry (Sassu et al, 2018). CpxAR Positively Regulates wecA Transcription aerosol and can infect swine of all ages (Sheehan et al, 2003). The Cpx TCS consists of the sensor kinase CpxA and the response regulator CpxR. Previous studies have reported that the CpxAR TCS enables bacteria to respond to envelope stress and environmental stresses such as oxidative and osmotic stress (Bury-Mone et al, 2009; Srinivasan et al, 2012; Bontemps-Gallo et al, 2015; Cao et al, 2018; Lopez et al, 2018; Matter et al, 2018)
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