Cationic bactericidal peptide 1018 does not specifically target the stringent response alarmone (p)ppGpp.

Liis Andresen,Vasili Hauryliuk,Tanel Tenson

doi:10.1038/srep36549

Liis Andresen, Vasili Hauryliuk + Show 1 more

Open Access

https://doi.org/10.1038/srep36549

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Journal: Scientific reports	Publication Date: Nov 7, 2016
Citations: 31	License type: CC BY 4.0

Affiliation: Umeå University, University of Tartu

Abstract

The bacterial stringent response is a key regulator of bacterial virulence, biofilm formation and antibiotic tolerance, and is a promising target for the development of new antibacterial compounds. The intracellular nucleotide (p)ppGpp acts as a messenger orchestrating the stringent response. A synthetic peptide 1018 was recently proposed to specifically disrupt biofilms by inhibiting the stringent response via direct interaction with (p)ppGpp (de la Fuente-Núñez et al. (2014) PLoS Pathogens). We have interrogated the specificity of the proposed molecular mechanism. When inhibition of Pseudomonas aeruginosa planktonic and biofilm growth is tested simultaneously in the same assay, peptides 1018 and the control peptide 8101 generated by an inversion of the amino acid sequence of 1018 are equally potent, and, importantly, do not display a preferential activity against biofilm. 1018 inhibits planktonic growth of Escherichia coli equally efficiently either when the alleged target, (p)ppGpp, is essential (MOPS media lacking amino acid L-valine), or dispensable for growth (MOPS media supplemented with L-valine). Genetic disruption of the genes relA and spoT responsible for (p)ppGpp synthesis moderately sensitizes – rather than protects – E. coli to 1018. We suggest that the antimicrobial activity of 1018 does not rely on specific recognition of the stringent response messenger (p)ppGpp.

Highlights

Peptide 1018 is efficient against biofilm and planktonic populations, as judged by crystal violet staining assay
In general, biofilms are much more resistant to antibacterial compounds than planktonic bacteria[20], the authors have concluded that an unusual molecular mechanism of action of 1018 is responsible for the peptide targeting biofilms
Effects on biofilms were studied on glass in flow cell chambers under conditions of constant medium flow[10]. This would allow for the sorption and accumulation of the peptides on the cell surface over time, and surface-specific sorption is a well-known property of cationic peptides[21]

Summary

Introduction

Results Peptide 1018 is efficient against biofilm and planktonic populations, as judged by crystal violet staining assay. In order to circumvent the above-mentioned issues we opted for a robust and widely adopted crystal violet (CV) staining assay that can measure both planktonic growth and biofilm formation in the same well of a 96-well plate[24,25].

Results

Conclusion