Effects of cefotaxime and kanamycin on thallus proliferation and differentiation in Porphyra yezoensis and their inhibition on Agrobacterium tumefaciens

The effects of two antibiotics such as cefotaxime and kanamycin on growth and differentiation of Porphyra yezoensis thalli and their inhibition on Agrobacterium tumefaciens were evaluated in order to develop an efficient technique for Agrobacterium-mediated genetic transformation. Cefotaxime at more than 500 mg/l and 300 mg/l resulted in suppression of P. yezoensis thallus growth and the formation of conchocelis, respectively, but kanamycin had no affects on P. yezoensis thallus growth at concentrations of 100-600 mg/l. The inhibition of antibiotics on P. yezoensis thallus differentiation was observed at cefotaxime concentration of more than 300 mg/l and kanamycin concentration of more than 600 mg/l, respectively, and no conchocelis were formed at these concentrations. Both of antibiotics possessed strong inhibition on A. tumefaciens growth. Cefotaxime at 200 mg/l significantly inhibited A. tumefaciens strains LBA4404 and AGL growth. Almost complete kanamycin suppressions on A. tumefaciens were observed at a concentration of above 400 mg/l in the culture medium. The results suggested that kanamycin could be used as both counter-selection of Agrobacterium and selectable markers via Agrobacterium-mediated transformation in P. yezoensis, and that cefotaxime could be used as counter-selection of Agrobacterium only.