title: Atomic Force Microscopy Reveals the Mechanobiology of Lytic Peptide Action on Bacteria.
abstract: Increasing rates of antimicrobial-resistant medically important bacteria require the development of new, effective therapeutics, of which antimicrobial peptides (AMPs) are among the promising candidates. Many AMPs are membrane-active, but their mode of action in killing bacteria or in inhibiting their growth remains elusive. This study used atomic force microscopy (AFM) to probe the mechanobiology of a model AMP (a derivative of melittin) on living Klebsiella pneumoniae bacterial cells. We performed in situ biophysical measurements to understand how the melittin peptide modulates various biophysical behaviors of individual bacteria, including the turgor pressure, cell wall elasticity, and bacterial capsule thickness and organization. Exposure of K. pneumoniae to the peptide had a significant effect on the turgor pressure and Young's modulus of the cell wall. The turgor pressure increased upon peptide addition followed by a later decrease, suggesting that cell lysis occurred and pressure was lost through destruction of the cell envelope. The Young's modulus also increased, indicating that interaction with the peptide increased the rigidity of the cell wall. The bacterial capsule did not prevent cell lysis by the peptide, and surprisingly, the capsule appeared unaffected by exposure to the peptide, as capsule thickness and inferred organization were within the control limits, determined by mechanical measurements. These data show that AFM measurements may provide valuable insights into the physical events that precede bacterial lysis by AMPs.
authors.affiliation: †School of Chemistry, ‡Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, and §Florey Institute for Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC 3010, Australia.
authors.forename: Anna
authors.initials: A
authors.lastname: Mularski
authors.affiliation: †School of Chemistry, ‡Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, and §Florey Institute for Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC 3010, Australia.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Wilksch
authors.affiliation: †School of Chemistry, ‡Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, and §Florey Institute for Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC 3010, Australia.
authors.forename: Huabin
authors.initials: H
authors.lastname: Wang
authors.affiliation: †School of Chemistry, ‡Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, and §Florey Institute for Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC 3010, Australia.
authors.forename: Mohammed Akhter
authors.initials: MA
authors.lastname: Hossain
authors.affiliation: †School of Chemistry, ‡Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, and §Florey Institute for Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC 3010, Australia.
authors.forename: John D
authors.initials: JD
authors.lastname: Wade
authors.affiliation: †School of Chemistry, ‡Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, and §Florey Institute for Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC 3010, Australia.
authors.forename: Frances
authors.initials: F
authors.lastname: Separovic
authors.affiliation: †School of Chemistry, ‡Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, and §Florey Institute for Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC 3010, Australia.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Strugnell
authors.affiliation: †School of Chemistry, ‡Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, and §Florey Institute for Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC 3010, Australia.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Gee
mesh_terms: D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000378:metabolism*; D001703:Biophysics; D007711:Klebsiella pneumoniae / Q000166:cytology / Q000378:metabolism*; D018625:Microscopy, Atomic Force
chemical_list: D023181:Antimicrobial Cationic Peptides