Phage N15 Research Articles

Evidence for extrachromosomal location of prophage N15

With the aid of temperature shift experiments, the ts mutants of temperate bacteriophage N15 were divided into two groups, early and late ones. Phage DNA replication is normal in late mutants at elevated temperature both in the vegetative and prophage states, whereas such replication is disturbed under the same condition in both states in early mutants. This disturbance results in the intensive curing of early mutant lysogens under nonpermissive conditions. Prophage N15 DNA sediments in sucrose gradients separately from bacterial DNA. The conclusion is drawn that prophage N15 is not incorporated into the bacterial chromosome. Some other properties of phage N15 and its DNA are described.

Isolation and characterization of bacteriophages for Neisseria.

SUMMARY Sixteen bacteriophages for several strains of Neisseria perflava were isolated from throat washings and lysogenic organisms. The phages are placed into five groups based on serological and host-range characteristics. Group I, host strain c r, has phages n1, n2, mutant n2c, n5, n6, and n13. n1 is virulent, all others temperate for the host. Plaque size is about 1·5 mm., the largest for Neisseria phages. Group II, host strains s, t and u, has phage n4 and mutant n4c. The neutralizable antigens of these phages are modified when the host is changed. The group III phages, n3, n7, n8, n9 and n11, are temperate for host strain t. Group III A has a single member, n10, which is temperate for its host, strain u. The group IV phages, n12, n155, n159 and n208, were all isolated from strains of N.flavescens on host strain s. Plaque size is about o-i mm., the smallest for the phages. All phages within a group are apparently serologically identical. Groups II, III and III A are serologically related, the others are distinct. The most remarkable feature is the extremely limited host range of each phage. Since the original chance isolations of the hosts given above, no additional phage-sensitive Neisseria have been found in over 300 strains tested.