AUTHOR=Yan Kang , Liu Ting , Duan Benzhen , Liu Feng , Cao Manman , Peng Wei , Dai Qi , Chen Huanchun , Yuan Fangyan , Bei Weicheng 

TITLE=The CpxAR Two-Component System Contributes to Growth, Stress Resistance, and Virulence of Actinobacillus pleuropneumoniae by Upregulating wecA Transcription

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.01026

DOI=10.3389/fmicb.2020.01026

ISSN=1664-302X

ABSTRACT=<p><italic>Actinobacillus pleuropneumoniae</italic> is the pathogen of porcine contagious pleuropneumonia. In <italic>A. pleuropneumoniae</italic>, 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 <italic>wecA</italic> in <italic>A. pleuropneumoniae</italic>. Our results revealed that CpxR positively regulates <italic>wecA</italic> expression by directly binding to the putative promoter region of <italic>wecA</italic>. Wild-type, Δ<italic>cpxAR</italic>, Δ<italic>wecA</italic>, and complemented strains were investigated under serum, oxidative, and osmotic stresses. The Δ<italic>cpxAR</italic> and Δ<italic>wecA</italic> 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 Δ<italic>cpxAR</italic> and Δ<italic>wecA</italic> 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 <italic>A. pleuropneumoniae</italic> growth, stress resistance, and virulence, by upregulating expression of <italic>wecA.</italic> Our findings provide new insight into the pathogenesis of <italic>A. pleuropneumoniae</italic>.</p>