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Transactivation of several genes of two native Serratia prophages after superinfection by phage kappa
Abstract:
Serratia marcescens HY bacteria must be lysogenic with either prophage y or psi to make it possible for phage kappa to form plaques unless they carry a so-called ink mutation. Genes in y and psi termed any and anp were identified that after infection of ink+ cells are necessary for an effective propagation of these phages as well as of coinfecting kappa phage. When kappa infects y and/or psi-lysogenic cells it transactivates the respective prophage genes by means of two early genes termed tay and tap. It appears that on infection of nonlysogenic ink+ cells kappa damps its own development, provided the regulatory region of the responsible gene is undermethylated. After kappa infection duly to achieve the special methylation of this region seems to be the function of any and anp. There are some more genes in y and psi prophage under the control of tay and tap, concerning in both cases a Dam methylation (recognition sequence GATC) of kappa DNA, a recombination proneness under restricting conditions of kappa DNA not modified by the modification enzyme of HY, and the kappa plaque size. By hybridization studies a region of homology common to y and psi was demonstrated which from its size might comprise all the transactivated genes. The view is supported by genetic data indicating an affinity among the any and anp genes. Investigation of various any mutants were indicative of DNA inversions in this region of the y genome. Surprisingly some of the any mutants had become sensitive in their plaque forming ability to an inhibitory activity exerted by prophage psi. Mutants of psi unable to interfere but still able to lysogenize were isolated. A model is presented accounting for the formation of pleiotropic and nonpleiotropic mutations with Any phenotype and their reversion types. Possible functions of the y genes and their counterparts in psi are discussed.
Insights
Bacteriophage kappa requires specific prophage genes (any and anp) in Serratia marcescens for plaque formation, involving DNA methylation and recombination control. These genes are activated by kappa
Area of Science:
- Bacteriology and Virology
- Molecular Genetics
- Microbial Ecology
Background:
- Serratia marcescens HY bacteria require lysogeny with prophage y or psi for bacteriophage kappa plaque formation, unless an ink mutation is present.
- Specific genes, any and anp, within prophages y and psi are crucial for effective phage propagation.
- Bacteriophage kappa infection triggers transactivation of these prophage genes via its own early genes, tay and tap.
Purpose of the Study:
- To identify and characterize genes in prophages y and psi essential for bacteriophage kappa propagation.
- To elucidate the mechanism of bacteriophage kappa's interaction with lysogenic and non-lysogenic Serratia marcescens.
- To investigate the roles of prophage genes in DNA methylation, recombination, and phage plaque size.
Main Methods:
- Bacterial genetics and phage infection experiments.
- Gene identification and characterization (any, anp, tay, tap).
- DNA hybridization studies to identify homologous regions between prophages.
- Analysis of various mutants (ink, any, psi) to understand gene function and interactions.
Main Results:
- Genes any (in y) and anp (in psi) are necessary for effective propagation of kappa and coinfecting phages in ink+ cells.
- Kappa transactivates y and psi prophage genes (tay, tap) in lysogenic cells; in non-lysogenic cells, kappa's development is damped unless specific DNA methylation occurs.
- Prophage genes under tay/tap control regulate Dam methylation of kappa DNA, recombination under restrictive conditions, and kappa plaque size.
- Homology between y and psi suggests a common region encompassing transactivated genes; genetic data support affinity between any and anp genes.
- Mutant analysis revealed DNA inversions in y, sensitivity to psi's inhibitory activity, and isolation of non-interfering psi mutants.
Conclusions:
- The any and anp genes play critical roles in bacteriophage kappa's life cycle, particularly in DNA methylation and host-phage interactions.
- A complex regulatory network involving kappa early genes and prophage genes controls phage development and propagation.
- The study provides a model for understanding pleiotropic and non-pleiotropic mutations and their reversion types in this phage-host system.