title: Characterization of cell surface and extracellular matrix remodeling of Azospirillum brasilense chemotaxis-like 1 signal transduction pathway mutants by atomic force microscopy.
abstract: To compete in complex microbial communities, bacteria must sense environmental changes and adjust cellular functions for optimal growth. Chemotaxis-like signal transduction pathways are implicated in the regulation of multiple behaviors in response to changes in the environment, including motility patterns, exopolysaccharide production, and cell-to-cell interactions. In Azospirillum brasilense, cell surface properties, including exopolysaccharide production, are thought to play a direct role in promoting flocculation. Recently, the Che1 chemotaxis-like pathway from A. brasilense was shown to modulate flocculation, suggesting an associated modulation of cell surface properties. Using atomic force microscopy, distinct changes in the surface morphology of flocculating A. brasilense Che1 mutant strains were detected. Whereas the wild-type strain produces a smooth mucosal extracellular matrix after 24 h, the flocculating Che1 mutant strains produce distinctive extracellular fibril structures. Further analyses using flocculation inhibition, lectin-binding assays, and comparison of lipopolysaccharides profiles suggest that the extracellular matrix differs between the cheA1 and the cheY1 mutants, despite an apparent similarity in the macroscopic floc structures. Collectively, these data indicate that disruption of the Che1 pathway is correlated with distinctive changes in the extracellular matrix, which likely result from changes in surface polysaccharides structure and/or composition.
authors.affiliation: Oak Ridge National Laboratory, Biosciences Division, Oak Ridge, TN, USA.
authors.forename: Amanda Nicole
authors.initials: AN
authors.lastname: Edwards
authors.forename: Piro
authors.initials: P
authors.lastname: Siuti
authors.forename: Amber N
authors.initials: AN
authors.lastname: Bible
authors.forename: Gladys
authors.initials: G
authors.lastname: Alexandre
authors.forename: Scott T
authors.initials: ST
authors.lastname: Retterer
authors.forename: Mitchel J
authors.initials: MJ
authors.lastname: Doktycz
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Morrell-Falvey
mesh_terms: D015806:Azospirillum brasilense / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000648:ultrastructure; D002633:Chemotaxis; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D018625:Microscopy, Atomic Force; D009154:Mutation; D011135:Polysaccharides, Bacterial / Q000378:metabolism*; D015398:Signal Transduction; D013499:Surface Properties
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D011135:Polysaccharides, Bacterial