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The dual M protein systems have diverse biological characteristics, but both contribute to M18-type Group A

Xiaorui Zhou1, Haoshuai Song1, Fei Pan1

  • 1MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China; Ministry of Agriculture Key Laboratory of Animal Bacteriology, Nanjing 210095, China.

Microbes and Infection
|August 19, 2023
PubMed

Insights

Group A Streptococcus (GAS) M18 strains utilize dual M protein systems. These systems, involving both GAS and GCS M proteins, are crucial for virulence and skin pathogenicity in these bacteria.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Pathogenesis

Background:

  • M protein is a critical surface virulence factor in Group A Streptococcus (GAS) and Group C Streptococcus (GCS).
  • M18-type GAS strains possess a unique dual M protein system, utilizing both GAS (emm18) and GCS (spa18) M proteins.
  • The spa18 gene in M18-type GAS is homologous to the GCS szm gene.

Purpose of the Study:

  • To investigate the biological characteristics and virulence contributions of the dual M protein systems in M18-type GAS.
  • To analyze the transcriptional regulation of the emm18 and spa18 genes.
  • To understand the distinct roles of M18 and SPA18 proteins in bacterial surface structure and host cell interactions.

Main Methods:

  • Comparative gene analysis of emm18 and spa18.
  • Construction and characterization of M18-type GAS mutants (Δemm18Δspa18).
  • Assessment of bacterial surface morphology using electron microscopy.
  • Evaluation of M18 and SPA18 protein binding properties and cytotoxicity.
  • Transcriptome analysis to identify regulatory factors.

Main Results:

  • spa18 shows higher transcription levels than emm18 in M18-type GAS.
  • A mutant lacking both M protein genes (Δemm18Δspa18) exhibits a smooth surface, unlike the rough surface of wild-type and single-mutant strains.
  • M18 and SPA18 proteins display distinct binding characteristics and differential cytotoxicity towards macrophages and keratinocytes.
  • Both emm18 and spa18 genes are essential for the skin pathogenicity of M18-type GAS.
  • The mga gene may regulate spa18 transcription, with SpyM18_2047 potentially playing a specific regulatory role.

Conclusions:

  • The dual M protein system in M18-type GAS significantly contributes to bacterial virulence and surface characteristics.
  • spa18 is a highly transcribed gene in this system and plays a vital role in pathogenicity.
  • Distinct functional properties of M18 and SPA18 proteins mediate interactions with host cells.
  • Transcriptional regulation of spa18 involves factors like mga and SpyM18_2047, offering insights into virulence factor control.
Keywords:
Bacterial pathogenicityBiological characteristicsGroup A StreptococcusM protein

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