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Lysogenic conversion in Klebsiella pneumoniae: system which requires active immunity regulation for expression of the
Abstract:
We have previously described Klebsiella pneumoniae MirM7b, which, although stably lysogenic for the inducible and nondefective phages FR2 and AP3, is not immune to superinfection by these same viruses. MirA12b, a strain which is lysogenic for FR2 and AP3 and immune to superinfection, has been derived from MirM7b. The sensitivity of this strain and that of the nonimmune parent to several bacteriophages have been compared in this work. It has been found that, whereas MirM7b is sensitive to coliphages P1, T3, T7, and phiI, MirA12b is fully resistant to all of them. It is shown that phages FR2 and AP3 convert Klebsiella strains to resistance to coliphage P1 and coliphages T3, T7, and phiI, respectively, and cause loss of surface antigens in lysogenic cells. To determine such a conversion, both FR2 and AP3 require expression of immunity to superinfection. This explains the differences that exist between MirM7b and MirA12b in both phage sensitivity and surface antigens. Hypotheses are presented to explain the peculiar need for an active superinfection repressor to express lysogenic conversion.
Insights
Lysogenic Klebsiella pneumoniae strains demonstrate altered phage resistance. Immunity to superinfection, conferred by phages FR2 and AP3, leads to resistance against coliphages P1, T3, T7, and phiI.
Area of Science:
- Microbiology
- Bacteriology
- Virology
Background:
- Klebsiella pneumoniae strains can be lysogenic, harboring bacteriophages.
- Lysogenic strains are typically immune to superinfection by the same phage.
- A previously described strain, MirM7b, is lysogenic but not immune to superinfection.
Purpose of the Study:
- To derive and characterize a Klebsiella pneumoniae strain immune to superinfection.
- To compare the bacteriophage sensitivity profiles of immune and non-immune lysogenic strains.
- To elucidate the role of superinfection immunity in lysogenic conversion.
Main Methods:
- Derivation of a superinfection-immune lysogenic strain (MirA12b) from a non-immune parent (MirM7b).
- Comparative sensitivity testing of MirM7b and MirA12b against various coliphages (P1, T3, T7, phiI).
- Analysis of surface antigen expression in lysogenic strains.
Main Results:
- MirA12b, the immune strain, exhibited full resistance to coliphages P1, T3, T7, and phiI, unlike the sensitive parent MirM7b.
- Bacteriophages FR2 and AP3 confer resistance to specific coliphages upon Klebsiella strains.
- Lysogenic conversion by FR2 and AP3 also results in the loss of surface antigens in lysogenic cells.
Conclusions:
- Superinfection immunity is essential for bacteriophages FR2 and AP3 to induce resistance to other coliphages and alter surface antigens.
- The observed differences in phage sensitivity and antigen profiles between MirM7b and MirA12b are explained by the presence or absence of superinfection immunity.
- The study suggests a requirement for an active superinfection repressor in expressing lysogenic conversion.