Finnish Fermented Milk “Viili”: Involvement of Two Cell Surface Proteins in Production of Slime by Streptococcus lactis ssp. cremoris

Abstract

The cell surface protein profile of the slime-forming, encapsulated (mucoid) Streptococcus lactis ssp. cremoris T5 from “viili” is compared with two variants of the same strain that do not produce slime: strain T5/30 was obtained by using an elevated growth temperature of 30°C and the nonmucoid strain T5/NS spontaneously at the growth temperature of 17°C. The profiles of cell surface proteins extractable by Triton X-100 were studied by the immunoblotting method. The spontaneous change of T5 phenotype to T5/NS brought about appreciable diminution in four and a loss in two cell surface polypeptides. Four of these, with molecular weights of 70,000, 54,000, 47,000, and 40,000, have previously been found to be located in the cell wall of two slime-forming, encapsulated strains. The polypeptides with molecular weights of 42,000 and 26,000 are present in the slime-forming mucoid variant T5 and also in T5/30 cells but absent from the nonmucoid T5/NS-cells. These two polypeptides may have some role in slime production and mucoidness and remain to be studied further. These analyses provide useful information for the purification and further characterization of surface antigens connected with slime production or excretion by the mucoid phenotype S. lactis ssp. cremoris and facilitate the selection of slime-forming variants for dairy starters. © 1988, American Dairy Science Association. All rights reserved.