title: Viscosity gradient within the mucus layer determines the mucosal barrier function and the spatial organization of the intestinal microbiota.
abstract: BACKGROUND
  Migration is an important virulence factor for intestinal bacteria. However, the role of bacterial mobility in the penetration of viscous mucus and their spatial organization within the colon is relatively unknown.
  
  
  METHODS
  Movements of fecal bacteria were assessed in gels of varying agarose concentrations and were compared with patterns of bacterial distribution observed in colons from conventional and Enterobacter cloacae-monoassociated mice. Bacteria were visualized using fluorescence in situ hybridization.
  
  
  RESULTS
  Long curly bacteria moved best in moderate viscosity gels, short rods and cocci preferred a low viscous environment, whereas high viscosity immobilized all bacterial groups. The spatial distribution of bacteria in the murine colon was also shape- and not taxonomy-dependent, indicating the existence of vertical (surface to lumen) and longitudinal (proximal to distal colon) viscosity gradients within the mucus layer. Our results suggest that mucus viscosity is low in goblet cells, at the crypt basis and close to the intestinal lumen, whereas sites adjacent to the columnar epithelium have a high mucus viscosity. The mucus viscosity increased progressively toward the distal colon, separating bacteria selectively in the proximal colon and completely in the distal colon.
  
  
  CONCLUSIONS
  The site-specific regulation of mucus secretion and dehydration make the mucus layer firm and impenetrable for bacteria in regions close to the intestinal mucosa but loose and lubricating in regions adjacent to the luminal contents. Selective control of mucus secretion and dehydration may prove to be a key factor in the management of chronic diseases in which intestinal pathogens are involved.
authors: Humboldt University, Charité Hospital, CCM, Laboratory for Molecular Genetics, Polymicrobial Infections and Bacterial Biofilms, Berlin, Germany. alexander.swidsinski@charite.de
authors: Alexander
authors: A
authors: Swidsinski
authors: Beate C
authors: BC
authors: Sydora
authors: Yvonne
authors: Y
authors: Doerffel
authors: Vera
authors: V
authors: Loening-Baucke
authors: Mario
authors: M
authors: Vaneechoutte
authors: Maryla
authors: M
authors: Lupicki
authors: Juergen
authors: J
authors: Scholze
authors: Herbert
authors: H
authors: Lochs
authors: Levinus A
authors: LA
authors: Dieleman
mesh_terms: D000818:Animals; D003106:Colon / Q000382:microbiology*; D016972:Enterobacter cloacae / Q000502:physiology; D005782:Gels; D017404:In Situ Hybridization, Fluorescence; D007413:Intestinal Mucosa / Q000502:physiology*; D051379:Mice; D014783:Viscosity
chemical_list: D005782:Gels