Actinobacillus pleuropneumoniae, the causative agent of porcine
pleuropneumonia, is capable of persisting in
oxygen-deprived surroundings, namely, tonsils and sequestered necrotic lung tissue. Utilization of alternative terminal electron acceptors in the absence of
oxygen is a common strategy in bacteria under anaerobic growth conditions. In an experiment aimed at identification of genes expressed in vivo, the putative catalytic subunit
DmsA of anaerobic
dimethyl sulfoxide reductase was identified in an A. pleuropneumoniae serotype 7 strain. The 90-kDa
protein exhibits 85% identity to the putative
DmsA protein of Haemophilus influenzae, and its expression was found to be upregulated under anaerobic conditions. Analysis of the unfinished A. pleuropneumoniae genome sequence revealed putative open reading frames (ORFs) encoding DmsB and
DmsC proteins situated downstream of the
dmsA ORF. In order to investigate the role of the A. pleuropneumoniae
DmsA protein in virulence, an isogenic deletion mutant, A. pleuropneumoniae DeltadmsA, was constructed and examined in an
aerosol infection model. A. pleuropneumoniae DeltadmsA was attenuated in
acute disease, which suggests that genes involved in oxidative metabolism under anaerobic conditions might contribute significantly to A. pleuropneumoniae virulence.