title: Morphological and functional adaptations of Fusobacterium nucleatum exposed to human neutrophil Peptide-1.
abstract: OBJECTIVE
  We recently demonstrated that Fusobacterium nucleatum can resist to human neutrophil peptide (HNP)-1 by decreasing its membrane permeability and increasing its proliferation and biofilm formation. In this continuation study, we aimed to further evaluate and explain these resistance properties by determining the morphological and functional adaptations of F. nucleatum, using transmission electron microscopy (TEM).
  
  
  METHODS
  Cultures of the type strain of F. nucleatum (ssp. nucleatum ATCC 25586) and two clinical strains (ssp. polymorphum AHN 9910 and ssp. nucleatum AHN 9508) were incubated without (0 μg/ml) or with four different test concentrations of recombinant HNP-1 (1, 5, 10 and 20 μg/ml). Membrane morphology and thickness, and cell (visualized by TEM), planktonic growth (measured in colony forming units), and biofilm formation (measured as total mass) were analyzed. Scrambled HNP-1 was used in planktonic growth and biofilm formation studies as a negative control.
  
  
  RESULTS
  TEM analyses revealed a decrease in the outer membrane surface corrugations and roughness of the strain AHN 9508 with increasing HNP-1 concentrations. In higher concentrations of HNP-1, the strain AHN 9910 showed thicker outer membranes with a number of associated rough vesicles attached to the outer surface. Intracellular granules became increasingly visible in the strain ATCC 25586 with increasing peptide concentrations. With increased concentrations of HNP-1, planktonic growth of the two clinical strains was significantly enhanced (P < 0.001) and of the type strain significantly suppressed (P < 0.01). HNP-1 decreased the biofilm formation of the two clinical strains, AHN 9910 (P < 0.01) and 9508 (P < 0.001) significantly. Scrambled HNP-1 showed no effect on planktonic growth or biofilm formation of the tested strains.
  
  
  CONCLUSIONS
  F. nucleatum has the ability to withstand the lethal effects of HNP-1, and the ultrastructural changes on bacterial membrane and cytoplasm may play role in this adaptive process.
authors.affiliation: Department of Periodontology, Institute of Dentistry, University of Turku, Turku, Finland. Electronic address: ahsamu@utu.fi.
authors.forename: Ahmed Ali
authors.initials: AA
authors.lastname: Musrati
authors.affiliation: Department of Periodontology, Institute of Dentistry, University of Turku, Turku, Finland.
authors.forename: Dareen
authors.initials: D
authors.lastname: Fteita
authors.affiliation: Department of Biomedicine, Laboratory of Anatomy, University of Turku, Turku, Finland.
authors.forename: Jorma
authors.initials: J
authors.lastname: Paranko
authors.affiliation: Department of Periodontology, Institute of Dentistry, University of Turku, Turku, Finland.
authors.forename: Eija
authors.initials: E
authors.lastname: Könönen
authors.affiliation: Department of Periodontology, Institute of Dentistry, University of Turku, Turku, Finland.
authors.forename: Ulvi Kahraman
authors.initials: UK
authors.lastname: Gürsoy
mesh_terms: D000222:Adaptation, Physiological; D001422:Bacterial Adhesion; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D002463:Cell Membrane Permeability / Q000187:drug effects; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D005674:Fusobacterium Infections / Q000382:microbiology; D016967:Fusobacterium nucleatum / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D046529:Microscopy, Electron, Transmission; D009504:Neutrophils / Q000378:metabolism; D010933:Plankton / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000494:pharmacology; D023084:alpha-Defensins / Q000096:biosynthesis / Q000494:pharmacology*
chemical_list: D011994:Recombinant Proteins; D023084:alpha-Defensins
keywords: Antimicrobial peptide; Biofilm; Planktonic; TEM; Ultrastructural changes