I am now doing the BAC(the larger alien DNA bank) position work, and i found that many pairs supported a larger possible block which looked not like chromosome DNA...
First Blast job i find that it is simllar to pOX1 in Ba...
My collegue did collecte those related contigs and found they assembled to a long one... it is really a good start...

i guess that largest plasmid in genome has a scalford most likily to pOX1 in Ba and gain the toxin gene because of IS231 family member insertion...