EXAMINATION OF SURFACE POLYSACCHARIDES OF ACTINOBACILLUS-PLEUROPNEUMONIAE SEROTYPE-1 GROWN UNDER IRON-RESTRICTED CONDITIONS

We investigated the expression of important Actinobacillus pleuropneum oniae surface polysaccharides, namely, capsular polysaccharides (CPS) and lipopolysaccharides (LPS), after growth under iron-restricted cond itions, Iron restriction did nor seem to affect the production of CPS, as determined by labelling with a monoclonal antibody (mAb) against t he serotype 1 K-antigen and flow cytometry analysis, and also as deter mined by electron microscopy. SDS-PAGE revealed that the LPS profiles of these cells were also unaffected by iron restriction. Using flow cy tometry analysis, however, we observed that binding of mAb against ser otype 1 O-antigen was altered in cells of A. pleuropneumoniae serotype 1 reference strain (4074) grown under iron-restricted conditions. Thi s strain exhibited two subpopulations with distinct patterns of reacti vity with the mAb against the O-antigen. When strain 4074 was grown un der iron-restricted conditions, a shift from one cell subpopulation (m oderately fluorescent) to another cell subpopulation (highly fluoresce nt, thus binding more antibodies) was observed. Our results indicate t hat growth of A. pleuropneumoniae serotype 1 under iron-restricted con ditions did not seem to affect CPS production, but might alter, at lea st for the reference strain, the expression of LPS.