Oral Presentation Lancefield International Symposium for Streptococci and Streptococcal Diseases 2025

Heterogeneous expression of the type VII secretion system in Streptococcus agalactiae (118071)

Victoria Gerber 1 , Camille Pétillon 1 , Anne-Sophie Renous 1 , Philippe Lanotte 1 2 , Laurent Mereghetti 1 2 , Eric Morello 1
  1. UMR1282-Infectiologie et Santé Publique-Université de Tours-INRAe-BRMF Team, Tours, France
  2. CHRU de Tours-Service de Bactériologie-Virologie-Hygiène, Tours, France

 

Background

Streptococcus agalactiae, or Group B Streptococcus (GBS), is one of the leading causes of neonatal infections. Type VII secretion system (T7SS) is a transmembrane multiprotein complex characterized in Gram-positive bacteria as an adaptation mechanism involved in interbacterial competition and/or virulence by secreting effectors (small α-helical proteins, toxins) in the environment [1-3]. Recent studies highlighted the heterogeneity of the T7SS locus, proposing the existence of four T7SS subtypes within the GBS strains [4,5].

Materials, methods

Promoter regions of the T7SS locus were identified in four different GBS strains using transcriptional fusion methods. RACE-PCR identified transcription initiation sites, and RT-PCR determined the co-transcription of the locus genes. The system's functionality was studied by Western blot detection of a predicted effector in different genetic backgrounds.

Results

Our work exhibits heterogeneity at the transcriptional and translational level of the T7SS locus between different GBS strains. The genes of the four T7SS subtypes are expressed under conventional laboratory culture conditions and have an operon-like organization where two active promoter regions have been identified, depending on the subtype. The aim is to identify the impact of this genetic variability on the overall functioning of the T7SS.

Conclusion

Taken together, these results should lead to the characterization of the T7SS in GBS to improve our understanding of the variability of colonization by different GBS strains of various resident microbiota. 

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