Genes from the exo–xis region of λ and Shiga toxin-converting bacteriophages influence lysogenization and prophage induction

Abstract

The exo–xis region, present in genomes of lambdoid bacteriophages, contains highly conserved genes of largely unknown functions. In this report, using bacteriophage λ and Shiga toxin-converting bacteriophage ϕ24Β, we demonstrate that the presence of this region on a multicopy plasmid results in impaired lysogenization of Escherichia coli and delayed, while more effective, induction of prophages following stimulation by various agents (mitomycin C, hydrogen peroxide, UV irradiation). Spontaneous induction of λ and ϕ24Β prophages was also more efficient in bacteria carrying additional copies of the corresponding exo–xis region on plasmids. No significant effects of an increased copy number of genes located between exo and xis on both efficiency of adsorption on the host cells and lytic development inside the host cell of these bacteriophages were found. We conclude that genes from the exo–xis region of lambdoid bacteriophages participate in the regulation of lysogenization and prophage maintenance.

ArgO145, a Stx2a prophage of a bovine O145:H- STEC strain, is closely related to phages of virulent human strains

“…Similarly, other authors could not identify these two genes in Stx2a phages from an O104:H4 EAHEC strain of the 2011 German outbreak (Beutin et al, 2012, from an O111:H2 EAHEC strain , and two O157:H7 STEC strains (Yin et al, 2015). The exo-xis region, that was proposed to participate in the regulation of lysogenization and the promotion of phage induction, also differs from those described in 933W and Φ24 b prophages (Bloch et al, 2013;Licznerska et al, 2016). Interestingly, despite the particular characteristics of early regulatory genes in ArgO145, phage titers were similar for strains EDL933 and FB5, both in basal and induced conditions.…”

Role of orf73 in the development of lambdoid bacteriophages during infection of the Escherichia coli host

“…Monitoring of phage lytic development during one round of infection of the E. coli host cells. Lytic cycle of the tested bacteriophages was studied in one-step growth experiments, according to the procedure described by Bloch and others (Bloch et al, 2013). Host bacteria were grown in the LB medium at 30 o C to A 600 =0.2.…”

“…These data indicated that overexpression of the exo-xis region impairs the lysogenization process and contributes to a decreased transcription from the cII-stimulated promoters p I , pa Q and p E , which are responsible for promotion of the lysogenic cycle (Łoś et al, 2008a). Moreover, a few years later it was demonstrated that more efficient induction of λ and Φ24 B prophages, induced by mitomycin C and hydrogen peroxide, occurred in cultures of host cells bearing a plasmid with the exo-xis region (Bloch et al, 2013). Following prophage induction, an increase in the phage DNA amount was significantly higher in lysogenic E. coli cells containing plasmid-borne exo-xis region, while survival rate of such bacteria was lower (Bloch et al, 2013 andBloch et al, 2014).…”

“…Moreover, a few years later it was demonstrated that more efficient induction of λ and Φ24 B prophages, induced by mitomycin C and hydrogen peroxide, occurred in cultures of host cells bearing a plasmid with the exo-xis region (Bloch et al, 2013). Following prophage induction, an increase in the phage DNA amount was significantly higher in lysogenic E. coli cells containing plasmid-borne exo-xis region, while survival rate of such bacteria was lower (Bloch et al, 2013 andBloch et al, 2014). These observations were supported by a finding that deletion of the phage exoxis region resulted in a dramatic decrease in the level of phage gene expression that are crucial for the lytic development of lambdoid viruses (Licznerska et al, 2016b).…”

Personality and genes: remarks from a biological perspective

“…Regulatory processes are indicated as thin arrows and thin blunt-ended lines (positive regulations are represented by arrows and negative regulations are represented by blunt-ended lines). This figure is an updated version of the scheme published by Węgrzyn, Licznerska, and Węgrzyn (2012), with included data reported by Bloch et al (2013), Kwan et al (2013), and Olszewski et al (2014).…”