Mutants of Salmonella anatum that block bacteriophage epsilon infection at early stages.

A total of six mutants, to which phage epsilon could adsorb but failed to lyse, were isolated from Salmonella anatum and characterized. A significant portion of active phage particles could be recovered from the phage-bacterium complexes before they became irreversibly absorbed, and adsorbed phage did not kill these mutants at all. These reversibly adsorbed phage had become sensitive to chloroform, at least in some cases. The results indicate that the steps that may be blocked are deoxyribonucleic acid ejection or penetration. The mutants were tentatively classified into three groups by their susceptibility to phages c341 and Felix O. The inhibition of phage infection was overcome by host range mutants of phages epsilon and c341. The isolated lipopolysaccharide from the parent strain inactivated phages epsilon, c341, and a host range mutant of epsilon in vitro. However, neither phage epsilon nor c341, or the host range mutant of phage epsilon, was inactivated by incubation with the mutant lipopolysaccharides, even when they were derived from the mutants susceptible to c341 or the host range mutant of epsilon. These results may suggest that more than the receptor lipopolysaccharide of the bacterial surface is involved in the early stages of phage infection.