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Published on: September 5, 2013
Variation of M protein with sequential transfer of group A streptococci in semisynthetic media
Abstract:
The growth and production of M protein by 18 strains of Streptococcus pyogenes of different M types were compared in semisynthetic media having either starch or Tween 80 as binders of oleic acid and either acid-hydrolysed casein or casitone as a source of amino acids. Most strains of M-type 12 showed substantial loss of M protein synthesis within several sequential transfers in the casein hydrolysate-Tween (CH-Tw) medium, but M protein synthesis was brough to its original concentration by a single transfer to semisynthetic medium to which 4% (v/v) horse serum or 50% (v/v) Todd Hewitt broth had been added. Six of eight strains of M-type 22 showed a complete loss of M antigen within one ortwo transfers in the CH-Tw medium. Re-initiation of M protein synthesis required the presence of both Todd Hewitt broth and horse serum. No evidence was found correlating loss of M protein to synthesis of proteinase since proteinase was not formed in the CH-Tw medium. Although the genetic loss of M protein synthesis did occur with one strain, the experimental results emphasized that variation in specific concentration of M protein or cessation of its synthesis resulted primarily from the absence of nutritional factors regulating its synthesis.
Insights
Nutritional factors, not genetic changes, primarily affect Streptococcus pyogenes M protein production. Supplementing media with horse serum or Todd Hewitt broth restored M protein synthesis in M-type 12 and M-type 22 strains.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Streptococcus pyogenes produces M protein, a key virulence factor.
- M protein expression is crucial for serotyping and understanding pathogenesis.
- Variations in M protein production can impact bacterial virulence and host immune response.
Purpose of the Study:
- To investigate the influence of nutritional factors on M protein production in Streptococcus pyogenes.
- To compare M protein synthesis in different semisynthetic media.
- To determine the conditions required for re-initiation of M protein synthesis.
Main Methods:
- Culturing 18 strains of Streptococcus pyogenes in various semisynthetic media.
- Comparing M protein production using different oleic acid binders (starch, Tween 80) and amino acid sources (acid-hydrolysed casein, casitone).
- Assessing M protein synthesis after sequential transfers and supplementation with horse serum or Todd Hewitt broth.
Main Results:
- Most M-type 12 strains lost M protein synthesis in casein hydrolysate-Tween (CH-Tw) medium, but recovered with serum or broth addition.
- Six of eight M-type 22 strains lost M antigen in CH-Tw medium; re-initiation required both serum and broth.
- No correlation between M protein loss and proteinase synthesis was observed.
Conclusions:
- Nutritional deficiencies in media, not genetic mutations, are the primary cause of M protein synthesis cessation.
- Specific nutritional factors regulate M protein concentration and synthesis in Streptococcus pyogenes.
- Horse serum and Todd Hewitt broth are essential for re-initiating M protein synthesis in certain strains.
