|Abstract or Summary
- The bacteriophage receptor of lactococci was found on the cell
walls. A carbohydrate analysis of the cell walls from phage-resistant
mutants of L. lactis subsp. cremoris KR with reductions in phage binding
indicated that a loss of galactose correlated with a loss in binding
and infection of all phage tested: kh, 643, 1, c2 and m13. In addition,
a loss of rhamnose correlated with a reduction in binding of phages kh
and m13. Inhibition studies of phage binding by lectins specific to
galactose suggested that phage kh does not bind directly to galactose.
Incubation of any of the five phages with 0.5M rhamnose, but not
galactose, completely inactivated the phage. Addition of rhamnose to
a growing liquid culture infected with all five phages or with phage kh
inhibited the infection. This suggested that the receptor of phage for
L. lactis subsp. cremoris KR is the rhamnose of the extracellular
In a similar analysis, phage skl was found to require rhamnose and
glucose of the extracellular polysaccharide of L. lactis subsp. lactis C2 for binding. The lectin studies suggests that phage ski does not
bind directly to glucose. The partial inhibition of phage ski infection
when rhamnOse, but not glucose, was added to a liquid culture suggests
that phage ski binds directly to the rhamnose.
The phage-resistant mutants isolated from superinfections of L.
lactis subsp. lactis C2 with phage c2 did not form plaques, but bound
normally to phage c2. The sensitivity of these mutants to phage ski was
also reduced significantly. In another analysis of mutants isolated
from superinfections with phage skl, none formed plaques with either
phage c2 or skl, but bound normally to both phages. The mutations
affected the cell membrane, as the membrane from wild type, but not from
phage-resistant cells, inactivated phage c2. The phage-inactivation
activity was eliminated by treatment with a protease, but not a
glycosidase. The partially purified phage-inactivating protein was
found to have an apparent molecular weight of 350,000 under nondenaturing
conditions and an apparent subunit size of 32 kDa. It is
proposed that a multimeric complex of the 32 kDa protein is required for
phage c2 and skl infection of strain C2.