title: Does water activity rule P. mirabilis periodic swarming? I. Biochemical and functional properties of the extracellular matrix.
abstract: The dynamics of bacterial colonies is complex in nature because it correlates the behavior of numerous individual cells in space and time and is characterized by emergent properties such as virulence or antibiotics resistance. Because there is no clear-cut evidence that periodic swarming of P. mirabilis colonies is ruled by chemical triggers responsible for cell-to-cell signaling in most of the biofilms, we propose that the observed periodicity relies on the colony's global properties. Hence, the biochemical and functional properties of the extracellular matrix (ECM) of P. mirabilis colonies were investigated. A binary exopolysaccharide mixture (1 and 300 kDa), glycinebetaine, and a phenoglycolipid were identified. Rheology, calorimetry, and water sorption experiments performed on purified EPS bring evidence that these exoproducts exhibit marked viscoelasticity, which likely relies on large scale H bond networks. Such behavior is discussed in terms of water activity because the mechanical ECM properties were found to depend on hydration.
authors.affiliation: Laboratoire des Polymères, Propriétés aux Interfaces et Composites, Université de Bretagne-Sud, Campus de Tohannic, BP573 56017 Vannes Cedex, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Lahaye
authors.forename: Thierry
authors.initials: T
authors.lastname: Aubry
authors.forename: Nelly
authors.initials: N
authors.lastname: Kervarec
authors.forename: Philippe
authors.initials: P
authors.lastname: Douzenel
authors.forename: Olivier
authors.initials: O
authors.lastname: Sire
mesh_terms: D005109:Extracellular Matrix / Q000737:chemistry*; D008055:Lipids / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods / Q000592:standards; D010316:Particle Size; D011513:Proteus mirabilis / Q000737:chemistry* / Q000502:physiology; D012015:Reference Standards; D012680:Sensitivity and Specificity; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D008055:Lipids; D014867:Water