PCR detection and schematic diagram of partial SeseCisland_3 deletion. (A) PCR detection of genes located in SeseCisland_3 deleted region (markers are 2000 bp, 1000 bp, 750 bp, 500 bp, 250 bp and 100 bp), the number of genes corresponds to Additional file 8: Table S8. (B) Genomic organization of the partial SeseCisland_3 deletion locus and its flanking repeat sequences in Sz35246. The fragment from 1551608 to 1580213 was knocked out, including the zeta toxin (PezT) and epsilon antitoxin (PezA) genes. The deleted region started with a Tn5252 transposon protein gene and is flanked by two repeated regions. After the reciprocal recombination, only one repeat region remained.