Polarity of envelope growth and heterogeneity of the outer membrane of Brucella abortus

PhD thesis defended by Victoria VASSEN (Prof. Xavier DE BOLLE) - 23/11/2018

Prof. Xavier DE BOLLE, UNamur, Research Unit in Biology of Microorganisms (URBM)


Jean-François COLLET (UCL), Ignacio MORIYON (University Pamplona), Alessandra POLISSI (University Milan), Jean-Yves MATROULE (UNamur), président, Xavier DE BOLLE (UNamur), promoteur


The cell envelope of Gram-negative bacteria is composed of outer membrane (OM) with lipopolysaccharides (LPS) on the outer leaflet, periplasm hosting peptidoglycan, and inner membrane. Brucella abortus belongs to the order of Rhizobiales, all of which display a specific mode of growth, namely unipolar growth. The new pole and the constriction site were proposed as incorporation sites of new envelope material in Rhizobiales. The localization of incorporation sites of new material was studied by using specific probes to label the different cell envelope layers. Besides, the mobility of the OM components was investigated on a long-range distance. The structure of the OM was explored in nanometer resolution using atomic force microscopy (AFM) and the revealed structures could be correlated to specific OM components by fluorescence microscopy. The detailed study of the OM on single cells will contribute to establish a physiological heterogeneous model of the OM.