Morphological and functional adaptations of Fusobacterium nucleatum exposed to human neutrophil Peptide-1

• Published in: Anaerobe Vol. 39; pp. 31 - 38
• Main Authors: Musrati, Ahmed Ali, Fteita, Dareen, Paranko, Jorma, Könönen, Eija, Gürsoy, Ulvi Kahraman
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-06-2016
• Subjects: Adaptation, Physiological; alpha-Defensins - biosynthesis; alpha-Defensins - pharmacology; Antimicrobial peptide; Bacterial Adhesion; Biofilm; Biofilms - drug effects; Biofilms - growth & development; Cell Membrane - drug effects; Cell Membrane - metabolism; Cell Membrane - ultrastructure; Cell Membrane Permeability - drug effects; Cytoplasmic Granules - drug effects; Cytoplasmic Granules - metabolism; Cytoplasmic Granules - ultrastructure; Dose-Response Relationship, Drug; Fusobacterium Infections - microbiology; Fusobacterium nucleatum; Fusobacterium nucleatum - drug effects; Fusobacterium nucleatum - isolation & purification; Fusobacterium nucleatum - metabolism; Fusobacterium nucleatum - ultrastructure; Humans; Microscopy, Electron, Transmission; Neutrophils - secretion; Plankton - drug effects; Plankton - metabolism; Plankton - ultrastructure; Planktonic; Recombinant Proteins - biosynthesis; Recombinant Proteins - pharmacology; TEM; Ultrastructural changes; Biofilm; Ultrastructural changes; Planktonic; TEM; Antimicrobial peptide
• ISSN: 1075-9964; 1095-8274
• DOI: 10.1016/j.anaerobe.2016.02.008

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).
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.
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.
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.
•Fusobacterium nucleatum is able to resist human neutrophil peptides (HNPs) in in vitro conditions.•TEM analyses regarding the morphological changes of F. nucleatum in response to HNP-1 are statistically significant.•The increase in the planktonic growth may explained as defense strategies of F. nucleatum against HNPs.•Scrambled HNP-1 has no effect on planktonic growth or biofilm formation of the tested strains.