FIG 4 .
S. alvi wkB2 has three Rhs loci with architectures congruent with extensive toxin domain replacement. (A) Size and structure of S. alvi wkB2 Rhs genes and cognate immunity genes, shown as arrows outlined in dark and light blue, respectively. A dashed line indicates the location of the conserved DPXG(18)DPXG motif, which marks the start of the C-terminal toxin domain in each toxin. PAAR, RhsA, and toxin domains were predicted through the NCBI CDD search (E value, <10−5). (B) Arrangement of Rhs loci in the wkB2 genome. Arrows show the 5′-to-3′ orientation of the loci, while dark and light blue ribbons connect >500-bp regions with >95% and >90% nucleotide identity, respectively. Rhs and cognate immunity genes are highlighted in dark and light blue, respectively; putative mobile genetic elements are yellow; and hypothetical genes are gray. Major tick marks occur every 10,000 bp; minor tick marks occur every 1,000 bp.