Bacteriophage adenine methyltransferase: a life cycle regulator? Modelled usingVibrio harveyimyovirus like

Abstract

Summary The adenine methyltransferase (DAM) gene methylates GATC sequences that have been demonstrated in various bacteria to be a powerful gene regulator functioning as an epigenetic switch, particularly with virulence gene regulation. However, overproduction of DAM can lead to mutations, giving rise to variability that may be important for adaptation to environmental change. While most bacterial hosts carry a DAM gene, not all bacteriophage carry this gene. Currently, there is no literature regarding the role DAM plays in life cycle regulation of bacteriophage. Vibrio campbellii strain 642 carries the bacteriophage Vibrio harveyi myovirus like (VHML) that has been proven to increase virulence. The complete genome sequence of VHML bacteriophage revealed a putative adenine methyltransferase gene. Using VHML, a new model of phage life cycle regulation, where DAM plays a central role between the lysogenic and lytic states, will be hypothesized. In short, DAM methylates the rha antirepressor gene and once methylation is removed, homologous CI repressor protein becomes repressed and non‐functional leading to the switching to the lytic cycle. Greater understanding of life cycle regulation at the genetic level can, in the future, lead to the genesis of chimeric bacteriophage with greater control over their life cycle for their safe use as probiotics within the aquaculture industry.

Molecular Characterization of a Novel Temperate Sinorhizobium Bacteriophage, ФLM21, Encoding DNA Methyltransferase with CcrM-Like Specificity

“…Bochow and colleagues proposed that Dam-like methylation plays an important role in the switching between lytic and lysogenic life cycles in VHML and the other phages of Vibrio spp., since most of the vibriophages contain the dam gene. However, this relationship has not yet been demonstrated experimentally (64). Despite many examples of the presence of genes encoding Dam-specific enzymes in the genomes of Gammaproteobacteria bacteriophages, the function of these MTases is still not well understood.…”

DNA Methylation

“…When the host dam gene is eliminated from the chromosome of E. coli O157:H7, there is no detectable chromosomal GATC methylation indicating repression of the prophage dam genes [53]. The role of phage-encoded Dam in the life cycle remains obscure as is also the case for Vibrio phages [54]. …”

The diverse genetic switch of enterobacterial and marine telomere phages

“…For V. campbellii phage VHML, a new hypothetical model of phage life cycle regulation has been proposed. 11 According to this sequence-based model, a VHML-encoded adenine methyltransferase (DAM) methylates a rha antirepressor gene located on the phage genome. The VHML Rha antirepressor has homology with the Rha antirepressor of phage phi80.…”

“…[11][12][13][14][15] Particularly notable is the fact that unlike the siphoviridal phages N15, PY54 and fKO2, marine telomere phages are members of the family Myoviridae. However, even though there are only partial protein similarities between enterobacterial and marine telomere phages, all these phages share a similar genome organization (Fig.…”