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

Department of Biochemistry, University of Oulu, Linnanmaa, SF-90570 Oulu, Finland

Raili Forsén¹

National Public Heath Institute, Oulu, PO Box 310, SF-90101 Oulu, Finland

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 T₅/3O 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 T₅/3O cells but absent from the nonmucoid T₅/NS-cells. These two polypeptides 5have 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.

¹ Address for correspondence.