Mechanisms Mediating Bactericidal Properties and Conditions That Enhance the Potency of a Broad-Spectrum Oligo-Acyl-Lysyl

Abstract

Previous studies have established the potential of the oligo-acyl-lysyl (OAK) concept in generating simple chemical mimics of host defense peptides (HDPs) with improved antimicrobial properties. We investigated the antibacterial properties of such an OAK, C 16(7) -KK-C 12 -K amide , to obtain a better understanding of the complex mode(s) of action of cationic antibacterial peptides. The average MIC, determined against a multispecies panel of 50 strains, was 6 ؎ 5 g/ml. However, although the OAK exerted an essentially dose-dependent bactericidal effect (time-kill curves typically exhibited 99% death within 2 h), marked differences in the killing rates occurred among inter-and intraspecies strains. Mechanistic comparison between equally sensitive and related strains revealed death of one strain to stem from the OAK's capacity to breach the cell membrane permeability barrier, whereas the death of the related strain resulted from the OAK's direct interference with DNA functions in vivo, without detectable membrane damage. These findings therefore support the notion that the antibacterial mechanism of action of a single HDP can vary among inter-and intraspecies strains. In addition, we present data illustrating the differential effects of environmental conditions (pH, ionic strength and temperature), on the OAK's antibacterial properties, and ultimately demonstrate potency enhancement (by orders of magnitude) through selection of optimal incubation conditions. Such attributes might be useful in a variety of antibacterial applications.

Amphibian antimicrobial peptide fallaxin analogue FL9 affects virulence gene expression and DNA replication in Staphylococcus aureus

“…At acidic pH, however, the susceptibility of FL9 was hampered. This has also been observed for the membrane-active AMP dermaseptin and the two OAKs (Yaron et al, 2003;Rydlo et al, 2006;Goldfeder et al, 2010;Sarig et al, 2011). Environmental conditions can hamper the effect of AMPs; however, FL9 maintained its activity under several conditions relevant for food production, pointing to a potential use of FL9 as lead compound for the future development of antimicrobial compounds used in the food industry.…”

“…Some AMPs that inhibit DNA synthesis bind nonspecifically to DNA. For example, the amphibian AMP, the a-helical AMP buforin II, can penetrate the cell membrane without causing its disruption, and inhibits cellular functions by binding to nucleic acids (Park et al, 1998;Kobayashi et al, 2000;Rotem et al, 2008;Sarig et al, 2011;Gottschalk et al, 2013). Therefore, to investigate whether the inhibition of DNA synthesis could be due to the binding of FL9 to bacterial DNA, a gel retardation assay was performed.…”

“…In addition to membrane disruption, several studies have shown that some AMPs also have the ability to traverse the cytoplasmic membrane and target intracellular molecules such as DNA and RNA (Brogden, 2005;Jenssen et al, 2006;Peschel & Sahl, 2006;Makobongo et al, 2012 interaction of AMPs with DNA may damage DNA and induce the SOS response (Gunderson & Segall, 2006;Rotem et al, 2008;Sarig et al, 2011). The SOS regulon comprises genes essential for DNA repair and restart of stalled or collapsed replication forks.…”

Antibacterial Properties of an Oligo-Acyl-Lysyl Hexamer Targeting Gram-Negative Species

“…Such a design allows systematic and gradual variations of charge and hydrophobicity and the dissection of their individual importance. Available data on the structure-activity relationships (SARs) of OAKs suggest their usefulness in improving understanding of the molecular basis for potency and selectivity (13,17,18). Recent designs have, moreover, shown potential for systemic efficacy (4,19,27), including upon coencapsulation with antibiotics in lipid vesicles (7,20).…”

Design, synthesis and evaluation of peptides and peptidomimetics inhibiting the bacterial DsbA-DsbB interaction

“…In fact, a single broad-spectrum OAK might present several distinct antibacterial mechanisms, depending on the pathogen species and strain. Against two different strains of E. coli, C16(ω7)K-β12 (similar to C12(ω7)K-β12 but with 4 extra carbons on the N-terminal acyl chain) acted differently by triggering cell death through membrane depolarization or by impeding biosynthesis through directly binding DNA (Sarig et al, 2011). Different modes of action for different OAKs also imply that different bacterial resistance mechanisms were triggered.…”