Peptide Ligands of AmiA, AliA, and AliB Proteins Determine Pneumococcal Phenotype.

Fauzy Nasher,Manfred Heller,Fernando Aguilar,Suzanne Aebi,Lucy J Hathaway,Peter W M Hermans

doi:10.3389/fmicb.2018.03013

Abstract

The Ami-AliA/AliB oligopeptide permease of Streptococcus pneumoniae has been suggested to play a role in environmental sensing and colonisation of the nasopharynx by this human bacterial pathogen by binding peptides derived from bacterial neighbours of other species in the microbiota. Here, we investigated the effects of the peptide ligands of the permease’s substrate binding proteins AmiA, AliA, and AliB on pneumococcal phenotype. AmiA and AliA ligands reduced pneumococcal growth, increased biofilm production and reduced capsule size. In contrast, AliB ligand increased growth and greatly increased bacterial chain length. A decrease in transformation rate was observed in response to all three peptides. Changes in protein expression were also observed, particularly those associated with metabolism and cell wall synthesis. Understanding interspecies bacterial communication and its effect on development of colonising versus invasive phenotypes has the potential to reveal new targets to tackle and prevent pneumococcal infections.

Highlights

Streptococcus pneumoniae is one of the most extensively studied microorganisms, but this opportunistic pathogen remains a major causative agent of several human diseases including otitis media, pneumonia, sepsis and bacterial meningitis
The pneumococcus is more often a harmless inhabitant of the human nasopharynx, a niche it shares with many other microorganisms. Sensing of these microbial neighbours has been proposed to occur by binding of short peptides of these other bacterial species by S. pneumoniae via oligopeptide binding proteins of ATP-binding cassette (ABC) transporters (Hathaway et al, 2014)
Strain D39 and its mutants were cultured overnight in BHI+foetal calf serum (FCS) medium until OD600nm = 0.5 100 μL sub-cultured into 10 mL of chemically defined medium (CDM) and grown to an OD600nm = 0.2, the culture was split into two 5 mL aliquots and 0.5 mg/mL of peptides were added to one sample and incubated for 15 min at 37◦C

Summary

INTRODUCTION

Streptococcus pneumoniae (pneumococcus) is one of the most extensively studied microorganisms, but this opportunistic pathogen remains a major causative agent of several human diseases including otitis media, pneumonia, sepsis and bacterial meningitis. One ABC transporter, the Ami-AliA/AliB permease, has been suggested to play a role in uptake of environmental signals and in competence for genetic transformation (Claverys et al, 2000) One of these permease’s oligopeptide binding proteins, AliB, has been shown to aid in colonisation of the nasopharynx in a mouse model (Kerr et al, 2004). For the three substrate binding proteins of the AmiAliA/AliB permease, we have shown recently that AmiA binds peptide AKTIKITQTR, matching an amino acid sequence found in 50S ribosomal subunit protein L30; AliA binds peptide FNEMQPIVDRQ, matching an amino acid sequence found in 30S ribosomal protein S20 and AliB binds peptide AIQSEKARKHN, matching an amino acid sequence found in 30S ribosomal protein S20 (Nasher et al, 2018b) These AmiAliA/AliB peptide ligands are found in multiple bacterial species in the class of Gammaproteobacteria which includes common colonisers of the nostrils and nasopharynx (Pettigrew et al, 2012; Biesbroek et al, 2014; Mika et al, 2015; Teo et al, 2015). Effects were found on growth, capsule size, chaining, transformation rate, and biofilm as well as on the pneumococcal proteome

Ethics Statement

RESULTS

DISCUSSION