I'm trying, since 6 months or so, to transform my bacterial cells (commercially available: i.e DH5alpha, DH10B, XL1-Blue and/or SURE.I've check the ligation reaction (3 times more moles of insert than vector for a least 500ng total DNA!!!) and everything is OK: we can see an up-shift.Unfortunetly I get nothing or some contamination: i.e. a bacterial specie that is (depending on the strain used) ApR CmR KanR StrepR and/or TetR !!! thismonster should be a Pseudomonas sp. The media used or always freshly made and at correct antibio. final concentration. The cells used are viable and competent (I usually get a lawn after a transfo with less thant 0,5ug of the vector). This is it, so if there's someone on the globe that can give me some advise you're desesperately WELCOME.
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