The Role of luxS in the Middle Ear Streptococcus pneumoniae Isolate 947.

Alexandra Tikhomirova,Kimberley T Mclean,Claudia Trappetti,Erin B Brazel,James C Paton,Hannah N Agnew

doi:10.3390/pathogens11020216

Abstract

The LuxS protein, encoded by luxS, is required for the production of autoinducer 2 (AI-2) in Streptococcus pneumoniae. The AI-2 molecule serves as a quorum sensing signal, and thus regulates cellular processes such as carbohydrate utilisation and biofilm formation, as well as impacting virulence. The role of luxS in S. pneumoniae biology and lifestyle has been predominantly assessed in the laboratory strain D39. However, as biofilm formation, which is regulated by luxS, is critical for the ability of S. pneumoniae to cause otitis media, we investigated the role of luxS in a middle ear isolate, strain 947. Our results identified luxS to have a role in prevention of S. pneumoniae transition from colonisation of the nasopharynx to the ear, and in facilitating adherence to host epithelial cells.

Highlights

Agnew, H.N.; Paton, J.C.; Trappetti, C.Streptococcus pneumoniae colonizes the nasopharynx of up to 97% of infants [1], and frequently this colonization is asymptomatic [2]
We have previously shown that S. pneumoniae clinical isolates, which are closely related genomically and belong to the same serotype and multi locus sequence type (MLST), may display distinct virulence phenotypes in mice, in accordance with their original site of isolation in humans as well as different capacities to utilize carbon sources [14,15]
To distinguish between true quorum sensing (QS) effects mediated by autoinducer 2 (AI-2) from the indirect consequences of luxS disruption on the activated methyl cycle, we examined the capacity of various concentrations of exogenous AI-2 to complement the growth defect of luxS

Summary

Introduction

H.N.; Paton, J.C.; Trappetti, C.Streptococcus pneumoniae colonizes the nasopharynx of up to 97% of infants [1], and frequently this colonization is asymptomatic [2]. Pertinent to S. pneumoniae persistence on mucosal surfaces, such as in the nasopharynx and middle ear, is its ability to form a biofilm community [5,6]. Biofilms exhibit a highly sophisticated structure whereby bacteria can exchange metabolic signals and communicate via a series of small peptide and diffusible autoinducer (AI) molecules. These molecules induce changes in gene expression in target cells in a density-dependent fashion to help the establishment and maintenance of a biofilm. Such interactions are grouped under the general term quorum sensing (QS)

Objectives

Methods

Results

Conclusion