Effects of colistin on surface ultrastructure and nanomechanics of Pseudomonas aeruginosa cells.
Chronic lung infections in cystic fibrosis patients are primarily caused by Pseudomonas aeruginosa. Though difficult to counteract effectively, colistin, an antimicrobial peptide, is proving useful. However, the exact mechanism of action of colistin is not fully understood. In this study, atomic force microscopy (AFM) was used to evaluate, in a liquid environment, the changes in P. aeruginosa morphology and nanomechanical properties due to exposure to colistin. The results of this work revealed that after 1 h of colistin exposure the ratio of individual bacteria to those found to be arrested in the process of division changed from 1.9 to 0.4 and the length of the cells decreased significantly. Morphologically, it was observed that the bacterial surface changed from a smooth to a wrinkled phenotype after 3 h exposure to colistin. Nanomechanically, in untreated bacteria, the cantilever indented the bacterial surface significantly more than it did after 1 h of colistin treatment (P-value = 0.015). Concurrently, after 2 h of exposure to colistin, a significant increase in the bacterial spring constant was also observed. These results indicate that the antimicrobial peptide colistin prevents bacterial proliferation by repressing cell division. We also found that treatment with colistin caused an increase in the rigidity of the bacterial cell wall while morphologically the cell surface changed from smooth to wrinkled, perhaps due to loss of lipopolysaccharides (LPS) or surface proteins.
Mortensen
Ninell P
NP
Danish Polymer Centre, Risoe National Laboratory, Technical University of Denmark, DK-4000 Roskilde, Denmark.
Fowlkes
Jason D
JD
Sullivan
Claretta J
CJ
Allison
David P
DP
Larsen
Niels B
NB
Molin
Søren
S
Doktycz
Mitchel J
MJ
D023181:Antimicrobial Cationic Peptides / Q000737:chemistry; D018929:Cell Culture Techniques / Q000379:methods; D003091:Colistin / Q000737:chemistry*; D007700:Kinetics; D008070:Lipopolysaccharides / Q000737:chemistry; D018625:Microscopy, Atomic Force / Q000379:methods; D008858:Microscopy, Phase-Contrast / Q000379:methods; D049329:Nanostructures / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods; D010641:Phenotype; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D012984:Software; D013499:Surface Properties; D013997:Time Factors
D023181:Antimicrobial Cationic Peptides; D008070:Lipopolysaccharides; D003091:Colistin