Cell surface proteins of encapsulated Streptococcus cremoris: identification and immunochemical characterization

Area of Science:

• Microbiology
• Biochemistry
• Food Science

Background:

• Slime-forming encapsulated Streptococcus cremoris strains are key in fermented dairy products like viili.
• Understanding the cell surface proteins of these strains is crucial for characterizing their properties and functions.

Purpose of the Study:

• To extract and characterize cell surface proteins from two slime-forming Streptococcus cremoris strains (MLS96 and T5).
• To identify common protein antigens and investigate their association with cell wall components and slime formation.

Main Methods:

• Non-ionic detergent Triton X-100 was used for cell surface protein extraction.
• Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting were employed for protein characterization.
• Antisera against whole Streptococcus cremoris cells were used for antigen recognition.

Main Results:

• Seven prominent polypeptides were common to both Streptococcus cremoris strains and recognized by antisera.
• Five of these polypeptides (70,000, 54,000, 50,000, 47,000, and 40,000 Da) were identified as cell wall components.
• Two additional polypeptides (42,000 and 26,000 Da) were identified and are under further study for their role in slime formation.

Conclusions:

• Modified Triton X-100 extraction is a suitable method for isolating surface-associated antigens from lactic streptococci.
• The study identified key cell wall proteins and potential slime-associated proteins in Streptococcus cremoris.
• Further research on the 42,000 and 26,000 Da polypeptides is warranted to elucidate their role in slime formation.