Regulation of the synthesis of M protein by sugars, Todd Hewitt broth, and horse serum, in growing cells of Streptococcus pyogenes.

The research article discusses the effects of different types of sugars on the synthesis of M protein during the growth of Streptococcus pyogenes, a bacterium causing strep throat and other illnesses. It has been discovered that M protein synthesis is preferably induced by glucose among other types of sugars and depends on the metabolic process by which glucose is used.

Testing the Effects of Different Sugars on M Protein Synthesis

• The researchers experimented with different sugars to see how they affect the rate of synthesis of M protein in the bacterial strain Streptococcus pyogenes 0055 M12T12.
• In a base of a semisynthetic medium, it was found that glucose promotes a high rate of M protein synthesis. Sucrose and trehalose, on the other hand, led to decreasing rates of synthesis. However, the growth rate of the bacteria remained relatively equal regardless of the type of sugar used.
• Interestingly, the researchers noted a period of increased M protein synthesis during the lag phase of growth and in the stationary period when the substrates were being exhausted.

The Role of Glucose in Sugar Utilization and M Protein Production

• Despite inhibiting the use of other sugars, glucose did not cause apparent diauxie, a phenomenon in which one sugar is consumed preferentially to another. However, the synthesis of M protein did exhibit strong diauxic curves, with a reduction in the synthesis rate seen while using the second sugar.
• It was also observed that 2-deoxyglucose caused a strong, permanent repression of M protein synthesis when glucose was the substrate, but only temporary repression when sucrose was the substrate.
• The addition of Todd Hewitt broth (a nutritional boost) allowed the bacteria to grow on phosphorylated sugars, though it did not promote the synthesis of M protein when a phosphorylated sugar was the sole substrate.

Impact of Horse Serum and Cyclic AMP

• Horse serum was found to increase the rate of M protein synthesis in a way that was very similar to cyclic AMP, a molecule used for intracellular signaling. However, the researchers suggested that cyclic AMP itself might not be the effector in horse serum based on quantitative analysis.
• Further, the researchers observed that the addition of phosphorylated sugars and glucose or sucrose as substrates strongly repressed M protein synthesis, with glucose-1-phosphate and fructose 1,6-diphosphate being the most repressive.

Conclusions

• Most importantly, the research concluded that the synthesis of M protein, while not necessary for the bacteria’s growth, was preferentially triggered by glucose compared to other sugars, and depended on how glucose was metabolically utilized.
• This finding could have further implications for understanding the metabolic behaviour and growth of Streptococcus pyogenes, thus offering potential implications for therapeutic targets against this bacterium.