Description
๐งฌ Cefotaxime Sodium โ a third-generation cephalosporin used to eliminate Agrobacterium after co-cultivation in plant transformation protocols. The antibiotic of choice because it has minimal phytotoxicity compared to carbenicillin.
| ๐งช CAS | 64485-93-4 | โ๏ธ MW | 477.44 g/mol |
| ๐ฌ Grade | TC / Microbiological | ๐ก๏ธ Storage | โ20 ยฐC; use within 2 weeks once dissolved |
๐งฌ Why cefotaxime after Agrobacterium co-cultivation?
After co-cultivation, living Agrobacterium cells continue to infect plant tissue, causing bacterial overgrowth that kills the culture. Cefotaxime kills Agrobacterium by inhibiting cell wall synthesis (ฮฒ-lactam mechanism) โ importantly, it does NOT select for transformed plants (kanamycin does that) but eliminates the bacteria. Uniquely, cefotaxime has minimal phytotoxicity even at high concentrations and โ unlike carbenicillin โ does not promote adventitious shoot growth.
๐งซ Working concentrations
| Use | Concentration | Notes |
|---|---|---|
| Standard Agrobacterium elimination | 100โ250 mg/L cefotaxime | Add to selection medium for 2โ4 weeks |
| Stringent elimination (recalcitrant spp) | 250โ500 mg/L | For persistent Agrobacterium |
| Combined with kanamycin (selection) | 200 mg/L cef + 50 mg/L kan | Dual purpose |
| Tobacco transformation (classic) | 100โ250 mg/L | Regeneration medium |
๐งช Stock prep
Dissolve in sterile distilled water. Prepare 200 mg/mL stock, filter-sterilise, aliquot (1 mL) and store at โ20 ยฐC. Thawed aliquots are stable at 4 ยฐC for 2 weeks. Do not autoclave.
โ ๏ธ Never autoclave cefotaxime โ heat degrades the ฮฒ-lactam ring. Always add by filter-sterilised stock to cooled medium. Cefotaxime degrades at RT within 24โ48 hours in solution โ always use fresh stocks.
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