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Synthesis of M protein by group A hemolytic streptococci in completely synthetic media during steady-state growth
Abstract:
Strains of type 6 (S 43) and type 14 group A streptococci were grown with M-protein production in the presence of chemically defined synthetic media slightly modified from that previously employed for the growth of a nonproducer of M protein (type 4). The M protein, which is associated with virulence in group A streptococcus, was previously produced in growing cultures only with complex media. The bacterial growth with the biosynthesis of M protein in synthetic medium was obtained by successive adaptation in steady-state culture with decreasing amounts of Todd-Hewitt broth. The synthesis continued for at least 480 generations at pH 7.3 and with a generation time of 84 min. Glucose was the limiting nutrilite and the concentration of reducing agents in the medium was critical. The M protein was identified by gel diffusion against type-specific antisera from the Communicable Disease Center and from R. Lancefield. The yield of M protein obtained from organisms grown in the continuous-culture device was comparable to that from standard broth stationary cultures.
Insights
Researchers successfully grew M protein-producing group A streptococci in a synthetic medium, a significant advancement for studying bacterial virulence factors. This method enables sustained M protein biosynthesis for extended bacterial generations.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Biochemistry
Background:
- M protein is crucial for group A streptococcus virulence.
- Previously, M protein production required complex media, limiting research.
- This study aimed to enable M protein biosynthesis in a defined synthetic medium.
Purpose of the Study:
- To develop a chemically defined synthetic medium for M protein production in group A streptococci.
- To achieve sustained bacterial growth and M protein biosynthesis in vitro.
- To identify critical factors for M protein synthesis in a controlled environment.
Main Methods:
- Adaptation of Streptococcus strains (types 6 and 14) to a modified synthetic medium via successive steady-state cultures.
- Utilizing a continuous-culture device for bacterial growth and M protein production.
- Monitoring bacterial growth, generation time, pH, and M protein identification via gel diffusion.
Main Results:
- Successful M protein production in a chemically defined synthetic medium.
- Sustained M protein synthesis for at least 480 generations under specific conditions (pH 7.3, 84 min generation time).
- Identified glucose as the limiting nutrient and reducing agent concentration as critical for M protein biosynthesis.
Conclusions:
- Chemically defined synthetic media can support M protein production in group A streptococci.
- This advancement facilitates further research into M protein's role in virulence.
- The continuous-culture method yields M protein comparable to traditional broth cultures.