Carbenicillin Disodium Salt is a semi-synthetic penicillin antibiotic with a carboxyl and benzyl group. Its mechanism of action is the same as ampicillin. It interferes with cell wall synthesis of gram-negative bacteria while displaying low toxicity to plant tissues. Gibco Carbenicillin is used as a selective antibiotic for resistant agrobacterium and E. coli, generally at a concentration of 50–100 μg/mL. The β-lactamase (bla) gene, which confers resistance to ampicillin, also confers resistance to carbenicillin. It is broken down more slowly by beta-lactamase compared to ampicillin, thus is more stable. It can reduce the growth of satellite colonies during long-term incubations. This product is provided as a powder and should be made into a stock solution of 50–100 mg/mL in water.