evaluation of spirulina platensis resistance to different antibiotics to find a selectable marker for genetic transformation

background spirulina is one of the most profitable known microalgae in the world, which is used as food and superfood. in the other hand, spirulina is a useful source of healthy components. it seems that the spirulina is transformable so that the introduction of a selectable marker is needed. objectives the purpose of this study was to determine a suitable selection marker for spirulina platensis. thus, this experiment was designed to survey the response of spirulina to different concentrations of candidate antibiotics including kanamycin, hygromycin, phosphinothricin, chloramphenicol and streptomycin in standard zarrouk medium. materials and methods s. platensis culture matched to 1 mcfarland standard and its resistance to different antibiotics was studied by serial dilution of kanamycin, hygromycin, phosphinothricin, chloramphenicol and streptomycin. biomass was detected after 7days using spectrophotometer and related growth graphs were illustrated. results fresh culture of s. platensis reached to exponential phase on day 4 of experiment. while this phase was presented on day 5 for cultures containing kanamycin or hygromycin. the spirulina cultured in medium supplied with basta, did not reach to growth phase however, chloramphenicol can stop the growth of spirulina cells. spirulina showed resistance to streptomycin with the concentration of 40 mg/l and higher. therefore, streptomycin can use as selectable marker to detect gm (genetic modified) spirulina spp. conclusions the streptomycin can be used as suitable selection marker in comparison with other introduced markers. for using this selectable marker, integration of a streptomycin resistant gene is needed. the gene aada is a potential candidate. the aada gene can be expressed under the control of upstream and downstream elements of s. platensis.