Gene organization of Type VI Secretion System (T6SS) gene clusters. (A) Large T6SS gene clusters. (B) Small T6SS gene clusters. Blocks of related genes are shaded grey. Putative core genes are colored green, putative effectors red, putative signal transducers black, conserved genes between clusters grey and genes without related or homologues in all other clusters white. The frameshift in EPYR_02110/EPYR_02111 is indicated by a red flash.