Please can someone help me make sense of this 
We were given 2 samples of bacteria and had to determine if either was a newly emerged strain by testing for an additional portion of DNA. So added EcoR1 then ran gel electrophoresis and I've attached the results.
Wells 1 and 2 were the two samples undigested and 3 & 4 the digested. What I don't understand is that the undigested forms of the plasmids haven't travelled further than the digested, I thought if they were supercoiled they moved more easily through the agarose than when linear.
I can understand that the plasmid in well 3 would move further as it is smaller after excision of the additional DNA but why has well 4 also moved further when nothing was removed.. Or has it been?
Also I would expect the undigested plasmid containing the additional DNA to travel more slowly than the undigested form without but they look to be exactly the same.
are the furthest lines in wells 1 & 2 actually linear DNA and not supercoiled? If so, why would this be?
I hope this makes sense and very grateful for any input.