PlyB is a polarly located glycanase that cleaves the chains of EPS and has a profound impact in the matrix of the rhizobial biofilm

ALONSO, D.O.; ABDIAN, P.L.; VON BILDERLING, C.; RUSSO, D.M.; PIETRASANTA, L.I.; ZORREGUIETA, A.

Buenos Aires

Simposio; GlycoAR 2014; 2014

FIL-IByME-FCEyN

Rhizobium leguminosarum are soil bacteria involved in the fixation of atmospheric nitrogen in symbiosis with leguminous plants. These bacteria may adopt different lifestyles, growing on soil particles, on root hairs or within legume roots. During this complex life cycle R. leguminosarum forms biofilms, communities of microorganisms that live encased in a self produced polymeric matrix. We study the biofilm formed by R. leguminosarum under laboratory conditions, which may reflect its survival strategy in the rhizosphere. The main component of the biofilm matrix is an acidic exopolysaccharide (EPS), composed of Glc, Gal and GlcA in a 5:2:1 ratio, substituted with non carbohydrate residues. The length of EPS molecules is regulated during its biosynthesis and also by the activity of extracellular glycanases. These glycanases are secreted by a type I PrsDE secretion system and have been shown to be active only on the surface of EPS producing cells. Moreover we observed that PlyB is polarly located. We have previously observed a plyB mutant is affected in biofilm formation. Here, we compare strains with different levels of expression of PlyB and analyze by gel filtration and atomic force microscopy (AFM) the distribution of EPS molecules length, showing that PlyB activity is essential for the production of an EPS with a normal length distribution and biofilm formation.