Immunobiological effects of Streptococcus cremoris from cultured milk ‘viili’; application of human lymphocyte culture techniques

Protein-protein interactions among the components of the biosynthetic machinery responsible for exopolysaccharide production in Streptococcus thermophilus MR-1C

AIM

This study identified protein-protein interactions among the biosynthetic machinery responsible for exopolysaccharide (EPS) production in Streptococcus thermophilus MR-1C.

METHODS AND RESULTS

Protein-protein interactions were investigated using the yeast two-hybrid system. A strong protein-protein interaction was detected between the transmembrane activation protein Wzd and the protein tyrosine kinase Wze. Weaker protein-protein interactions were detected between two duplicate Wze proteins and between Wze and the phosphotyrosine phosphatase Wzh. Protein-protein interactions involving a Wzd/Wze fusion protein and Wzd and Wze may indicate that these proteins form multi-protein complexes. All combinations of the Wzh, Wzd, Wze, Wzg (regulation), CpsE (glycosyl-1-phosphate transferase), CpsS (polymerization), CpsL (unknown), CpsW (regulation) and CpsU (membrane translocation) were analysed for protein-protein interactions but no additional interactions were discovered using the yeast two-hybrid system.

CONCLUSIONS

Interactions among the phosphotyrosine phosphatase, tyrosine kinase, and transmembrane activation protein are important in the regulation of capsule biosynthesis in Strep. thermophilus MR-1C.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides some valuable insight into the organization and interactions between the many proteins involved in EPS production. A better understanding of this process may facilitate the genetic manipulation of capsule production to impart desirable properties to dairy starter cultures.

Enhancement of antigen-specific antibody production by extracellular slime products from slime-forming Lactococcus lactis subspecies cremoris SBT 0495 in mice

The effect of extracellular slime products (ESP) produced by Lactococcus lactis subspecies cremoris SBT 0495 on antigen specific antibody production was studied in mice. ESP contained 48.5% protein, 15.4% neutral sugar, and 1.1% of phosphorus. The optimum dose of ESP was between 100 to 500 micrograms per mouse. ESP administered intraperitoneally (200 micrograms per mouse) enhanced the production of specific antibody in mice. These results indicate that ESP may act as an adjuvant.

B-cell mitogen produced by slime-forming, encapsulated Lactococcus lactis ssp. cremoris isolated from ropy sour milk, viili

A substance, active as a B-cell mitogen, was isolated from the slime products produced by Lactococcus lactis ssp. cremoris KVS20. The mitogenic substance was prepared by anion-exchange chromatography and gel filtration chromatography and then purified by proteinase digestion and HPLC. Chemical analysis determined that the mitogenic substance was a phosphopolysaccharide and consisted of rhamnose, glucose, galactose, and phosphorus. The activity of the mitogenic substance was higher than that of the slime products. The optimal concentration for the activity was approximately 120 micrograms/ml. The mitogenic substance also had substantial mitogenic activity to spleen cells from C3H/HeJ mice, which are resistant to lipopolysaccharide. The findings indicated that a B-cell mitogen different from lipopolysaccharide is produced from L. lactis ssp. cremoris KVS20.