Cell surface characteristics of some phage‐resistant strains of Lactobacillus casei

The cell surface characteristics of two types of PL‐1 phage‐resistant strains of Lactobacillus casei: K‐12, which does not permit adsorption of the phage; and YIT 9021, which permits phage adsorption but not genome injection, were compared with those of the parent strain. There were no differences in the electron microscopic features of the cell surface. However, both the phage‐resistant strains were more hydrophobic than the parent strain as judged by hydrocarbon affinity test. A colloid titration test showed that these mutant strains were less negatively charged than the parent one. They differed in the composition of the polysaccharide of their cell walls, which were all free from teichoic acids.