Antibacterial Properties of Dermaseptin S4 Derivatives under Extreme Incubation Conditions

Abstract

Antibacterial properties of the frog-derived peptide dermaseptin S4 and a series of synthetic derivatives against the food pathogen Escherichia coli O157:H7 were investigated under extreme incubation conditions. The 28-mer analog K 4 K 20 S4 (P 28 ) displayed an MIC of 8 M and rapid bactericidal kinetics under standard culture conditions. Potent bactericidal properties were maintained at high salt concentrations, under acidic or basic conditions, and at extreme temperatures. The N-terminal 14-mer sequence (P 14 ) displayed higher potency (MIC, 4 M) but only within a narrow range of incubation conditions, pointing to the importance of the C-terminal domain of P 28 . The potency range was reextended upon conjugation of aminododecanoic acid to P 14 . The resulting lipopeptide was even more potent (MIC, 2 M) and affected bacterial viability under most of the conditions tested, including in commercial apple juice. The mechanistic implications of peptides' hydrophobicity, charge, structure, and binding to an idealized membrane were probed and are discussed here. Collectively, the data indicate interest in simple peptide-based compounds for design of antimicrobials that affect pathogens under a variable range of incubation conditions. Antimicrobial peptides (AMPs) are important components of innate immunity (23, 39, 52). Many are active towards a wide range of microorganisms by a mode of action which is still not fully understood but is assumed to involve interaction with the bacterial membrane and its disruption. AMPs do not require interaction with a chiral center for activity, supporting a lower probability for microorganisms to develop efficient resistance mechanisms compared with conventional antibiotics (22,38).AMPs from the dermaseptin family were recently proposed as model peptides for investigating the effects of acyl conjugation (13,17,44). These amphibian-derived AMPs (35, 36) have been amply investigated during the past decade and shown to exert rapid cytolytic activity against a wide range of microorganisms, including gram-negative and gram-positive bacteria, protozoa, filamentous fungi (14,26,35,36), spores of pathogenic bacteria (29), yeasts (11), and intracellular parasites (13,17,30), as well as antiviral activity (5).Due to its distinctive primary structure, dermaseptin S4 was used to identify structure-function relationships, which eventually led to potent derivatives (19,21,31,37,38). In recent work, we defined the activity of a single-amino-acid-substituted derivative, K 4 -S4, against Escherichia coli O157:H7 in terms of milieu dependencies (51). Extending that study, the present work is aimed at understanding the molecular elements in native dermaseptin S4 that are necessary for maintaining antimicrobial potency under extreme incubation conditions. We produced a set of derivatives that varied in length, composition, hydrophobicity, and net charge and investigated the effect of incubation conditions on the peptides' activity and bacterial susceptibility. In addition, we investigated the peptides' ...

Synthesis and antimicrobial activity of dermaseptin S1 analogues

“…Recent findings indicated that acylation of dermaseptin S4 fragments with long chain fatty acids, with or without an amino function in their structures, is well tolerated in terms of antimicrobial activity and is instrumental in modulating the potency and spectrum of activity in different assay conditions. 16,22 Compound 14 showed a small increase in MIC against S. aureus and maintained the same activity as DS1(1-15)-NH 2 against E. coli. Interestingly, the LD 50 against E. coli decreased about twofold with respect to that of DS1(1-15)-NH 2 indicating faster bactericidal kinetics.…”

“…15,16 In contrast to other S dermaseptin peptides, the 28-residue dermaseptin S4 is highly toxic to erythrocytes but, as noted by Feder et al 15 and Rydlo et al 16 , reducing hydrophobicity or by increasing the net positive charge improved peptide bioactivity. Shorter derivatives still displayed high antibacterial activity in vitro and in vivo along with a more acceptable toxicity profile against human erythrocytes, albeit still rather high.…”

“…Microorganisms were grown in static culture at 37°C in Mueller Hinton Broth (Oxoid) and diluted to 5 Â 10 5 CFU/mL. The MIC was determined using the microdilution serial twofold assay (from 100 lg/mL of each preparation) and performed in sterilized 96-well plates (Nunc) in a final volume of 200 lL 16,37 ; control wells without peptides were included. The MIC was considered the lowest peptide concentration that showed no increase in turbidity after overnight incubation at 37°C.…”

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.…”

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

“…However, this prediction about microbial resistance has since been criticized (Bell & Gouyon, 2003, Tzeng et al, 2005, Kraus & Peschel, 2006. A very large number of AMPs have been identified but apart from a few exceptions presently on the market (Leader et al, 2008) natural peptides offer little prospect as drug candidates for the following properties: 1) poor stability due to the sensitivity to proteases (with a lifetime of a few minutes in serum and tissues (Pollaro & Heinis, 2010)), 2) high sensitivity to pH and salts (Goldman et al, 1997, Bals et al, 1998, Rydlo et al, 2006, Lee et al, 1997, 3) their large size limiting large-scale manufacturing and 4) poor pharmacokinetics combined with high immunogenicity (Latham, 1999). These drawbacks have led to the generation of peptide analogues that can mimic AMP properties, so-called peptidomimetics.…”