Figure 1

Genetic organization of the putative corticoviral prophages, bacteriophage PM2 [19], and the maintenance region of the pAS28 plasmid [26]. Circular PM2 genome map is linearized at a unique EcoRII site [19]. Genes encoding structural and nonstructural proteins (Roman numerals) and ORFs (lower case letters) are visualized as arrows indicating the direction of transcription. The origin of replication (ORI) and the known promoters (kinked arrows) are indicated. All the elements are aligned to the major coat protein-coding gene II of phage PM2, except for the pAS28 maintenance region, which is aligned to the PM2 gene XVI. Genes in the corticoviral elements sharing sequence similarity with those of PM2 are named according to the previously established phage PM2 nomenclature [19] and are coloured blue. Genes in the PM2 genome, as well as in corticoviral elements related to those of the pAS28 plasmid, are coloured red. The viral "self" core, containing genes IX, VII, and II is shaded grey. The late promoter region of phage PM2 and the noncoding region matching its position in all putative prophages is coloured yellow. Recombinase-coding genes and genes encoding replication-associated proteins (other than XII- and ORF1-type) are shown in green and black, respectively. Putative CI repressor- and endolysin-coding genes, as well as the position of the DnaA protein-binding site, are indicated. As a reference point, accession numbers of putative coat proteins of the identified corticoviral prophages are indicated in parenthesis under the corresponding bacterial species name. While exact nucleotide positions of the depicted corticoviral elements can be found in the supplemental material table (see Additional file 1).