Antimicrobial activities of LL-37 and its truncated variants against Burkholderia thailandensis

Antimicrobial peptides (AMPs) are essential host defence molecules found in a wide variety of species
and are promising antibacterial therapeutic candidates. Focusing on the human cathelicidin peptide LL-
37, the aim of the present study was to explore the mechanisms of action and antimicrobial activities
of a library of LL-37 fragments using Burkholderia thailandensis E264 as a model. The results revealed
that IG-19 was the shortest fragment within LL-37 that exhibited antibacterial activity. LL-31, missing
six residues at the C-terminus of LL-37, exhibited the strongest killing effect. Freeze-fracture electron
microscopy of bacterial cells treated with either LL-37 or LL-31 revealed irregular bacterial surfaces with
bleb projections, indicating that these peptides disrupted the integrity of the membrane. In addition,
these peptides induced leakage of cell components, including nucleotides and even proteins. Altogether,
the results obtained indicate the potential of using LL-31 as a new AMP to combat Burkholderia spp.