title: Multiple EPS interactions involved in the cohesion and structure of aerobic granules.
abstract: This study aims to clarify the biochemical nature and interactions of Extracellular Polymeric Substances (EPS) involved in the structure and cohesive properties of aerobic granules. Granules were incubated with selective hydrolytic enzymes or with chemicals and the resistance of digested granules to shear stress was evaluated. After α-amylase digestion, the hydrodynamic stress released macro-particles (>315 μm) while soluble molecules (<1.5 μm) and micro-particles (1.5-315 μm) where mainly recovered after savinase and EDTA treatments. These data show that α (1-4) glucans and proteins are key polymers for granule cohesion and that divalent cationic bridging is a major aggregative mechanism. On the basis of these experiments and microscopy observations, a model is proposed for the spatial organization of EPS in the granular structure, in which α glucans are arranged in a capsular layer surrounding bacterial clusters while anionic proteins constitute the intercellular cement that may reinforce cohesion inside the bacterial clusters.
authors.affiliation: Université de Toulouse; UPS, LBAE, Laboratoire de Biotechnologies Agroalimentaire et Environnementale, EA 4565, Institut Universitaire de Technologie, 24 rue d'Embaquès, 32000 Auch, France.
authors.forename: Cédric
authors.initials: C
authors.lastname: Caudan
authors.affiliation: Université de Toulouse; INSA, UPS, INP; LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France; INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, F-31400 Toulouse, France.
authors.forename: Ahlem
authors.initials: A
authors.lastname: Filali
authors.affiliation: Université de Toulouse; INSA, UPS, INP; LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France; INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, F-31400 Toulouse, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Spérandio
authors.affiliation: Université de Toulouse; UPS, LBAE, Laboratoire de Biotechnologies Agroalimentaire et Environnementale, EA 4565, Institut Universitaire de Technologie, 24 rue d'Embaquès, 32000 Auch, France. Electronic address: elisabeth.neuhauser@iut-tlse3.fr.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Girbal-Neuhauser
mesh_terms: D000332:Aerobiosis; D001419:Bacteria / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D019149:Bioreactors; D002118:Calcium / Q000378:metabolism*; D006868:Hydrolysis; D011108:Polymers / Q000737:chemistry*; D011135:Polysaccharides, Bacterial / Q000378:metabolism*; D033081:Shear Strength
chemical_list: D001426:Bacterial Proteins; D011108:Polymers; D011135:Polysaccharides, Bacterial; D002118:Calcium
keywords: Aerobic granules; Aggregation; Alpha glucans; Anionic proteins; Divalent cationic bridging; Extracellular polymeric substances