Lambdoid recombination modules. Genes are indicated by pointed boxes drawn approximately to scale as follows: SSB (green), nuclease (red), SAP (orange), and anti-RecBCD (blue). Different shades of the same color indicate different sequence types. Pointed ends on the gene boxes indicate the direction of transcription. Vertical red brackets on the right indicate the 13 module types that encode the same combination of functions regardless of their sequence relationships; the prototype phage for each group (see Supplemental Table S4) is indicated in red text.