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Modulation of Lactobacillus casei bacteriophage A2 lytic/lysogenic cycles by binding of Gp25 to the early lytic mRNA
Author(s) -
Carrasco Begoña,
Escobedo Susana,
Alonso Juan C.,
Suárez Juan E.
Publication year - 2016
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.13234
Subject(s) - lytic cycle , lysogenic cycle , biology , lysogen , ribosomal binding site , bacteriophage , messenger rna , microbiology and biotechnology , lactobacillus casei , genetics , translation (biology) , virus , gene , escherichia coli , bacteria
Summary The genetic switch of L actobacillus casei bacteriophage A 2 is regulated by the CI protein, which represses the early lytic promoter P R and C ro that abolishes expression from the lysogenic promoter P L . Lysogens contain equivalent cI and cro‐gp25 m RNA concentrations, i.e., CI only partially represses P R , predicting a lytic cycle dominance. However, A 2 generates stable lysogens. This may be due to G p25 binding to the cro‐gp25 m RNA between the ribosomal binding site and the cro start codon, which abolishes its translation. Upon lytic cycle induction, CI is partially degraded, cro‐gp25 m RNA levels increase, and C ro accumulates, launching viral progeny production. The concomitant concentration increase of G p25 restricts cro m RNA translation, which, together with the low but detectable levels of CI late during the lytic cycle, promotes reentry of part of the cell population into the lysogenic cycle, thus explaining the low proportion of L . casei lysogens that become lysed (∼ 1%). A2 shares its genetic switch structure with many other Firmicutes phages. The data presented may constitute a model of how these phages make the decision for lysis versus lysogeny.