Physiological and Genetic Aspects of Abortive Infection of a Shigella sonnei Strain by Coliphage T7

AUTOR(ES)

Hausmann, R.

RESUMO

Phage T7 adsorbed to and lysed cells of Shigella sonnei D2 371-48, although the average burst size was only 0.1 phage per cell (abortive infection). No mechanism of host-controlled modification was involved. Upon infection, T7 rapidly degraded host deoxyribonucleic acid (DNA) to acid-soluble material. Phage-directed DNA synthesis was initiated normally, but after a few minutes the pool of phage DNA, including the parental DNA, was degraded. Addition of chloramphenicol, at the time of phage infection, prevented both the initiation of phage-directed DNA synthesis and the degradation of parental phage DNA. Addition of chloramphenicol 4.5 min after phage was added permitted the onset of phage-directed DNA synthesis but prevented breakdown of phage DNA. Mutants of T7 (ss− mutants) have been isolated which show normal growth in strain D2 371-48. Upon mixed infection of this strain with T7 wild type and an ss− mutant, infection was abortive; no complementation occurred. The DNA of the ss− mutants was degraded in mixed infection like that of the wild type. Revertant mutants which have lost their ability to grow on D2 371-48 were isolated from ss− mutants; they are, in essence, phenotypically like T7 wild type. Independently isolated revertants of ss− mutants did not produce ss− recombinants when they were crossed among themselves. When independently isolated ss− mutants were crossed with each other, wild-type recombinants were found; ss− mutants could then be mapped in a cluster compatible with the length of one cistron. We concluded that T7 codes for an active, chloramphenicol-sensitive function [ss+ function (for suicide in Shigella)] which leads to the breakdown of phage DNA in the Shigella host.

Documentos Relacionados

• ABORTIVE INFECTION OF A STRAIN OF ESCHERICHIA COLI BY COLIPHAGE T21
• Rescue of abortive T7 gene 2 mutant phage infection by rifampin.
• A single-base change in gene 10 of bacteriophage T7 permits growth on Shigella sonnei.
• Abortive Infection of F-Plasmid-Containing Escherichia coli Cells by Bacterial Virus T7 Is Determined by the Right End of T7 Gene 1
• Expression of the unassembled capsid protein during infection of Shigella sonnei by bacteriophage T7 results in DNA damage that is repairable by bacteriophage T3, but not T7, DNA ligase.