FIG 9.

CarolAnn genes 43 and 44 confer defense against Crossroads. (A) Genome comparison of mycobacteriophage Sbash and Gordonia phage CarolAnn. Shading between the genomes reflects nucleotide sequence similarities, although there are only two short regions of weak similarity at the extremities of Sbash 30 and CarolAnn 43. Sbash gp30/CarolAnn gp44 and Sbash gp31/CarolAnn gp43 homologous pairs share 50% and 43% amino acid identity, respectively. Sbash 30 and 31 are transcribed rightward and are displaced from the repressor gene (gene 43), whereas CarolAnn 43 and 44 are coexpressed with the repressor (gene 45). (B) Serial dilutions of Sbash, Crossroads, Pipsqueaks, and 12 Crossroads DEM mutants (labeled phggXXX) were plated onto lawns of M. smegmatis mc²155pMH94 (vector) and M. smegmatis mc²155pMM16, which carries CarolAnn genes 43 and 44.