Host specificity of DNA produced by Escherichia coli III. Effects on transduction mediated by λ dg
1964; Elsevier BV; Volume: 23; Issue: 2 Linguagem: Inglês
10.1016/0042-6822(64)90280-6
ISSN1096-0341
Autores Tópico(s)Bacterial Genetics and Biotechnology
ResumoTransducing phage λ dg carrying bacterial gal markers shows the same effects of host-controlled modification as does normal λ. Phage grown on Escherichia coli K12 is restricted (not accepted) on E. coli B and K12(P1), and phage grown on B is restricted on K12 and K12(P1) independently of whether the gal markers of λ dg originated from the K12 or B chromosome. Transduction to a restricting host yields a very low proportion of gal+ transductants, which are mostly heterogenotes. Superinfecting restricted λ phage does not exert helper functions for lysogenization or reproduction of nonrestricted λ dg particles. In cells infected with restricted λ dg and superinfected with nonrestricted λ a greatly increased transduction frequency is observed, probably due to marker rescue. A small helper effect is observed in cells infected with restricted λ dg and restricted λ, presumably caused by help in lysogenization in those few cells which accept the infecting λ dg. For nonrestricting hosts it is known that ultraviolet irradiated λ dg no longer transduces by lysogenization but by stable integration of the gal markers into the bacterial chromosome. The same behavior is found for restricting recipients. Here, the maximum number of stable transductants is not notably higher than the number of heterogenotic transductants obtained on the same bacteria infected with nonirradiated λ dg. This is in agreement with the notion that most of the restricted genomes are degraded after their injection. Particles giving rise to stable transduction show a very low UV sensitivity. The ease with which stable transduction occurs probably reflects the degree of homology between endo- and exogenotic gal regions.
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