CELL-SURFACE DIFFERENCES OF LACTOCOCCAL STRAINS

A number of cell surface properties were compared in 15 pairs of lacto coccal strains in order to gain an understanding of cell surface diver sity and the relationship between tire acquisition of the phage-resist ance phenotype and alteration of cell surface properties. Each pair co mprised a parent strain and a derivative resistant to a phage (O-R) or a number of phages. Three cell surface hydrophobicity patterns were f ound: (1) three parent strains were more hydrophobic than their O-R de rivatives; (2) five O-R derivatives were more hydrophobic than their p arent strains; (3) there were no differences for seven strain pairs. L oosely associated cell surface material was removed without cell lysis , find concentration differences between 28 strains of 40-, 23- and 11 -fold were found for the extracted protein, hexose and rhamnose, respe ctively. These three surface components were extracted in higher conce ntrations fr om tire O-R derivative for seven strain pairs and from th e parent strain for three strain pairs, and no differences were observ ed for four sri ain pairs. Intracellular and extracellular lipoteichoi c acid concentrations varied in four of six strain pairs studied. The extracted protein profiles determined on polyacrylamide gels and by Su perose 12 chromatography and the compositions of the extracted polysac charide were different between most of the strain pairs. In addition, the surface properties, particularly cell hydrophobicity, varied accor ding to growth conditions for some strains. The cell-surface component s showed considerable diversity within the 30 lactococcal strains stud ied, with multiple differences between many of the strain pairs. For e xample, differences in hydrophobicity, the extracellular lipoteichoic acid concentration, molecular weight profile of proteins and the amoun t of protein, hexose and rhamnose extracted as loosely associated cell surface material were observed between the strains of pair E8/398. No unifying theme was evident to describe the basis of changes to the ce ll surface in the phage-resistant derivative strains.