CHARACTERIZATION OF LOOSELY ASSOCIATED MATERIAL FROM THE CELL-SURFACEOF LACTOCOCCUS-LACTIS SUBSP CREMORIS-E8 AND ITS PHAGE-RESISTANT VARIANT STRAIN-398

Loosely associated material (LAM) was isolated by gentle extraction pr ocedures from the cell surface of Lactococcus lactis subsp. cremoris E 8 and its phage-resistant variant strain 398. LAM from both strains wa s chemically characterized, and its role in the adsorption of three sm all isometric bacteriophages, PHI 618, PHI 833, and PHI 852, to the ce ll surface of the two strains was investigated. The phage-resistant st rain (strain 398) produced LAM which differed significantly from the m aterial produced by the parent strain. The total yield of LAM from str ain 398 was two- to threefold higher than that from strain E8, and the material contained fivefold more rhamnose and twofold more galactose. Polyacrylamide gel electrophoretic analysis showed that LAM from stra in 398 lacked a 21-kDa protein which was present in LAM from the paren t strain. Inhibition studies of phage binding by using isolated LAM fr om two strains showed that although LAM from strain E8 reduced the tit er of PHI 618 and PHI 852 by 53 and 82% respectively, LAM from strain 398 had no effect on the plaque-forming ability of any of the three ph ages tested. Treatment of LAM from strain E8 with sodium metaperiodate destroyed its ability to bind with PHI 618 and PHI 852. Phenotypicall y, strain 398 differed from its parent strain E8 in that it was more p rone to cell lysis and required an osmotically adjusted buffer system for the extraction of LAM.