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The in vitro interaction of Streptococcus pyogenes with human pharyngeal cells induces a phage-encoded extracellular
Thomas B Broudy1, Vijaykumar Pancholi, Vincent A Fischetti
1Department of Bacterial Pathogenesis and Immunology, Rockefeller University, New York, New York 10021, USA. broudyt@rockefeller.edu
Abstract:
The role lysogenic bacteriophage play in the pathogenesis of the host bacterium is poorly understood. In a previous study, we found that streptococcal coculture with human pharyngeal cells resulted in the induction of lysogenic bacteriophage as well as the phage-associated streptococcal pyrogenic exotoxin C (SpeC). In this study, we have determined that in addition to SpeC induction, a number of other streptococcal proteins are also released by the bacteria during coculture with pharyngeal cells. Among these, we identified and characterized a novel 27-kDa secreted protein. Sequence analysis of this novel protein demonstrated it to be encoded by the same lysogenic bacteriophage which harbors speC. Protein sequence analysis revealed varied homologies with several streptococcal DNases. Further biochemical characterization of the recombinantly expressed protein verified it to be a divalent cation-dependent streptococcal phage-encoded DNase (Spd1). Although functionally distinct, SpeC and Spd1 are associated by a number of parameters, including genetic proximity and transcriptional regulation. Finally, we speculate on the induction of phage-encoded DNase (Spd1) enhancing the fitness of both bacteria and phage.
Insights
Lysogenic bacteriophages induce streptococcal pyrogenic exotoxin C (SpeC) and a novel DNase (Spd1) when grown with human cells. This phage-encoded DNase may enhance bacterial and phage fitness.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The role of lysogenic bacteriophages in bacterial pathogenesis is not well understood.
- Previous research indicated bacteriophage induction and SpeC release during Streptococcus coculture with human pharyngeal cells.
Purpose of the Study:
- To investigate other streptococcal proteins released during coculture with human pharyngeal cells.
- To identify and characterize a novel protein encoded by the lysogenic bacteriophage.
Main Methods:
- Coculture of Streptococcus with human pharyngeal cells.
- Protein identification and characterization using sequence analysis.
- Biochemical characterization of recombinant protein.
Main Results:
- A novel 27-kDa secreted protein, a streptococcal phage-encoded DNase (Spd1), was identified and characterized.
- Spd1 is a divalent cation-dependent DNase, genetically linked to SpeC.
- Both SpeC and Spd1 share transcriptional regulation.
Conclusions:
- Lysogenic bacteriophages can induce the release of multiple proteins, including DNases, during host cell interaction.
- The phage-encoded DNase (Spd1) may contribute to the fitness of both the bacterium and the bacteriophage.