Quorum Sensing

Chapter 7

Detection ofAgr-TypeAutoinducing Peptides

Produced byStaphylococcusaureus

Ewan J. Murray and Paul Williams

Abstract

Strains of the Gram-positive pathogenStaphylococcusaureuscan be divided into four quorum sensing (QS)
groups. Membership of each group is defined by the amino acid sequence of the autoinducing peptide
(AIP) QS signal molecule that is encoded within theagrBDCAgenetic locus and specifically withinagrD.
This chapter describes the use of simple, in-cell,lux-based, bio-reporters that can be used to identify/
confirm the specificagrgroup to which a particularS.aureusisolate belongs, as well as to assess the timing
and quantity of AIP produced.

Key wordsStaphylococcusaureus,Agr, Bio-reporter, Autoinducing peptide, Quorum sensing

1 Introduction

S.aureusis a human pathogen of major clinical concern [1]. The

emergence of multi-antibiotic-resistantS.aureusand other clini-

cally relevant bacteria has led to calls for the development of new

antibacterial strategies that target nonessential cellular processes

that would reduce the selective pressures that drive the emergence

of antibiotic-resistant isolates [2]. Bacterial cell-to-cell communi-

cation or quorum sensing (QS) is one such nonessential process

that has been targeted in an attempt to generate novel antibacterial

agents. This is because QS regulates virulence factor production in

many different pathogens. Ideally, any new therapy that targets QS

should silence bacterial communication, thus blocking the produc-

tion of virulence factors and reducing disease, and so offer the host

immune system extra time to clear an infection [3].

S.aureus and related Gram-positive bacteria including the

coagulase-negative staphylococci, enterococci, clostridia, and lis-

teria all use an autoinducing peptide (AIP)-based QS system to

“sense” their local population density [4–6]. InS.aureus, AIP-

dependent QS incorporates a typical auto-activation circuit that is

encoded by theagrBDCAgeneticlocus. The timing of activation of

Livia Leoni and Giordano Rampioni (eds.),Quorum Sensing: Methods and Protocols, Methods in Molecular Biology,
vol. 1673,https://doi.org/10.1007/978-1-4939-7309-5_7,©Springer Science+Business Media LLC 2018

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