title: Characterization of structures in biofilms formed by a Pseudomonas fluorescens isolated from soil.
abstract: BACKGROUND
  Microbial biofilms represent an incompletely understood, but fundamental mode of bacterial growth. These sessile communities typically consist of stratified, morphologically-distinct layers of extracellular material, where numerous metabolic processes occur simultaneously in close proximity. Limited reports on environmental isolates have revealed highly ordered, three-dimensional organization of the extracellular matrix, which may hold important implications for biofilm physiology in vivo.
  
  
  RESULTS
  A Pseudomonas spp. isolated from a natural soil environment produced flocculent, nonmucoidal biofilms in vitro with unique structural features. These mature biofilms were made up of numerous viable bacteria, even after extended culture, and contained up to 50% of proteins and accumulated 3% (by dry weight) calcium, suggesting an important role for the divalent metal in biofilm formation. Ultrastructurally, the mature biofilms contained structural motifs consisting of dense, fibrillary clusters, nanofibers, and ordered, honeycomb-like chambers enveloped in thin sheets.
  
  
  CONCLUSIONS
  Mature biofilms contained living bacteria and were structurally, chemically, and physiologically heterogeneous. The principal architectural elements observed by electron microscopy may represent useful morphological clues for identifying bacterial biofilms in vivo. The complexity and reproducibility of the structural motifs observed in bacterial biofilms appear to be the result of organized assembly, suggesting that this environmental isolate may possess ecological advantages in its natural habitat.
authors.affiliation: Department of Chemistry, Oak Crest Institute of Science, 2275 E, Foothill Blvd, Pasadena, CA 91107, USA. m.baum@oak-crest.org
authors.forename: Marc M
authors.initials: MM
authors.lastname: Baum
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Kainović
authors.forename: Teresa
authors.initials: T
authors.lastname: O'Keeffe
authors.forename: Ragini
authors.initials: R
authors.lastname: Pandita
authors.forename: Kent
authors.initials: K
authors.lastname: McDonald
authors.forename: Siva
authors.initials: S
authors.lastname: Wu
authors.forename: Paul
authors.initials: P
authors.lastname: Webster
mesh_terms: D001426:Bacterial Proteins; D018441:Biofilms / Q000254:growth & development*; D004269:DNA, Bacterial / Q000235:genetics; D050296:Microbial Viability; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D011551:Pseudomonas fluorescens / Q000302:isolation & purification / Q000502:physiology / Q000648:ultrastructure*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012988:Soil Microbiology
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S