Hi all

I was wondering if anyone ever came across a scenario where S aureus ΔRM Systems were working for electroporation and all of a sudden stopped. I had a batch stop working, so I threw it out streaked a new plate from the glycerol stock and redid the competent cells multiple times including the 1 I primarily used for the cells I used for a full year. All conditions were met the cells were stored in a -80, removed as needed and thawed on ice, DNA ranging 0.1 - 1.5 ug was used but no colonies, the Abx was tested on non plasmid carrying bacteria and its working when the cells themselves are grown with no selection pressure they grow, can anyone give any opinions as to what could be wrong?.

Ps the electroporator was tested on E coli and it works,