Inhibition of Competence Development, Horizontal Gene Transfer and Virulence in Streptococcus pneumoniae by a Modified Competence Stimulating Peptide

Luchang Zhu,Gee W Lau,Debra E Bessen

doi:10.1371/journal.ppat.1002241

Luchang Zhu, Gee W Lau + Show 1 more

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https://doi.org/10.1371/journal.ppat.1002241

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Journal: PLoS Pathogens	Publication Date: Sep 1, 2011
Citations: 117	License type: CC BY 4.0

Affiliation: University of Illinois Urbana-Champaign

Abstract

Competence stimulating peptide (CSP) is a 17-amino acid peptide pheromone secreted by Streptococcus pneumoniae. Upon binding of CSP to its membrane-associated receptor kinase ComD, a cascade of signaling events is initiated, leading to activation of the competence regulon by the response regulator ComE. Genes encoding proteins that are involved in DNA uptake and transformation, as well as virulence, are upregulated. Previous studies have shown that disruption of key components in the competence regulon inhibits DNA transformation and attenuates virulence. Thus, synthetic analogues that competitively inhibit CSPs may serve as attractive drugs to control pneumococcal infection and to reduce horizontal gene transfer during infection. We performed amino acid substitutions on conserved amino acid residues of CSP1 in an effort to disable DNA transformation and to attenuate the virulence of S. pneumoniae. One of the mutated peptides, CSP1-E1A, inhibited development of competence in DNA transformation by outcompeting CSP1 in time and concentration-dependent manners. CSP1-E1A reduced the expression of pneumococcal virulence factors choline binding protein D (CbpD) and autolysin A (LytA) in vitro, and significantly reduced mouse mortality after lung infection. Furthermore, CSP1-E1A attenuated the acquisition of an antibiotic resistance gene and a capsule gene in vivo. Finally, we demonstrated that the strategy of using a peptide inhibitor is applicable to other CSP subtype, including CSP2. CSP1-E1A and CSP2-E1A were able to cross inhibit the induction of competence and DNA transformation in pneumococcal strains with incompatible ComD subtypes. These results demonstrate the applicability of generating competitive analogues of CSPs as drugs to control horizontal transfer of antibiotic resistance and virulence genes, and to attenuate virulence during infection by S. pneumoniae.

Highlights

Streptococcus pneumoniae is one of the most important pathogens that cause bacterial pneumonia, otitis media, meningitis and sepsis [1,2,3]
The acquisition of antibiotic resistance genes in S. pneumoniae is controlled by a peptide pheromone called competence-stimulating peptide (CSP)
competence stimulating peptide (CSP) binds to a receptor called ComD, which in turn activates its cognate transcription factor ComE to initiate DNA uptake and integration into the S. pneumoniae genome

Summary

Introduction

Streptococcus pneumoniae is one of the most important pathogens that cause bacterial pneumonia, otitis media, meningitis and sepsis [1,2,3]. The acquisition and spread of antibiotic resistance genes in S. pneumoniae is at least partly due to genetic transformation, which occurs when the bacteria enter the competent state [7,8,9]. Upon interacting with CSP, ComD phosphorylates the cognate transcriptional regulator ComE [11,12,13]. ComE initiates the transcription of a set of 24 genes (early genes), including comX. As an alternative sigma factor, ComX positively regulates the transcription of 81 genes (late genes) in the competence regulon [14,15]. Some of these late genes encode effectors for DNA uptake and recombination [14].

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