Extracellular components that define Rhizobium leguminosarum biofilm matrix architecture

ABDIAN, P.; VOZZA, N.; CARAMELO, J.; VON BILDERLING, C.; RUSSO, D.M.; PIETRASANTA, L. ZORREGUIETA, A

Vienna

Congreso; Biofilms 6. International Conference on Microbial Biofilms; 2014

Universidad de Austria

Rhizobia are soil bacteria that interact with leguminous plants inducing nitrogen-fixing root nodules. They grow in varied environmental conditions producing different types of biofilms. We study the biofilms formed by R. leguminosarum in vitro, a process probably relevant to the attachment of cells to soil particles. The typical architecture of a mature biofilm consists of layers of cells attached to each other by lateral interactions, forming clusters interlaced by water channels. The main component of the matrix is an acidic exopolysaccharide (EPS) that provides support to the biofilm structure. Moreover R. leguminosarum produces a capsular polysaccharide (CPS) that seems involved in surface attachment at the onset of biofilm formation. Proteins secreted by a type I secretion system are also involved. Interestingly, some of them possess one or more cadherin-like domains that confer carbohydrate binding ability. Among them, we have characterized RapA2, a unipolar calcium binding lectin that specifically recognizes the EPS; and the Ply glycanases that regulate the length of EPS molecules. A characteristic distribution of EPS molecules length is important to build up an ordered polysaccharide network. A model depicting the interaction of RapA, Ply glycanases and acidic polysaccharides during the progress of biofilm matrix development is presented.