title: A multi-scale approach of the mechanisms underlying exopolysaccharide auto-organization in the Proteus mirabilis extracellular matrix.
abstract: For decades, the origin of the concentric ring pattern of bacterial swarming colonies has puzzled microbiologists. It was hypothesized that a periodic water activity variation originates a phase transition within the extracellular matrix water H bond network, which switches on and off the exopolysaccharide auto-organization. Both rheological and infrared spectroscopy measurements respectively performed at a molecular scale and on a currently migrating colony, have given a physical insight into the mechanisms which underlie the switch between swarming and consolidation phases. Thanks to in situ and real time infrared microspectroscopy, and thanks to the brilliance of the infrared beam at SOLEIL synchrotron, here we demonstrate that Proteus mirabilis swarming is triggered by a periodic variation of water activity at the colony edge. A dynamic behavior emerges from the global properties of the multicellular entity which relies on the ability of the bacterial cells to tune exoproduct synthesis in order to undergo sharp transitions at a given water activity threshold.
authors: Laboratoire d'Ingénierie des Matériaux de Bretagne, Université Européenne de Bretagne, Campus de Tohannic, BP573, 56017 Vannes CEDEX, France. osire@univ-ubs.fr.
authors: Élodie
authors: É
authors: Lahaye
authors: Yun
authors: Y
authors: Qin
authors: Frédéric
authors: F
authors: Jamme
authors: Thierry
authors: T
authors: Aubry
authors: Olivier
authors: O
authors: Sire
mesh_terms: D005109:Extracellular Matrix / Q000378:metabolism*; D006860:Hydrogen Bonding; D008859:Microscopy, Polarization; D011135:Polysaccharides, Bacterial / Q000737:chemistry / Q000378:metabolism*; D025341:Principal Component Analysis; D011513:Proteus mirabilis / Q000378:metabolism*; D012212:Rheology; D013055:Spectrophotometry, Infrared; D014867:Water / Q000737:chemistry
chemical_list: D011135:Polysaccharides, Bacterial; D014867:Water