Abstract:
:Natural antimicrobial peptides (AMPs) provide prototypes for the design of unconventional antimicrobial agents. Existing bulk assays measure AMP activity but do not provide details of the growth-halting mechanism. We use fluorescence microscopy to directly observe the attack of the human antimicrobial peptide LL-37 on single Escherichia coli cells in real time. Our findings strongly suggest that disruption of the cytoplasmic membrane is not the growth-halting mechanism. At 8 μM, LL-37 binding saturates the outer membrane (OM) within 1 min. Translocation across the OM and access to the periplasmic space (5-25 min later) correlates in time with the halting of growth. Septating cells are attacked more readily than nonseptating cells. The halting of growth may occur because of LL-37 interference with cell wall biogenesis. Only well after growth halts does the peptide permeabilize the cytoplasmic membrane to GFP and the small dye Sytox Green. The assay enables dissection of antimicrobial design criteria into two parts: translocation across the OM and the subsequent halting of growth.
journal_name
Proc Natl Acad Sci U S Aauthors
Sochacki KA,Barns KJ,Bucki R,Weisshaar JCdoi
10.1073/pnas.1101130108subject
Has Abstractpub_date
2011-04-19 00:00:00pages
E77-81issue
16eissn
0027-8424issn
1091-6490pii
1101130108journal_volume
108pub_type
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