Blasticidin S hydrochloride is widely used as a selective agent in cell culture systems, particularly for the selection of mammalian, bacterial, and fungal cells that have been genetically engineered to express resistance to the compound. It inhibits protein synthesis by interfering with the peptidyl transferase activity of the ribosome, making it highly effective in eliminating non-resistant cells during stable transfection experiments. It is commonly used in research involving gene expression, CRISPR/Cas9 editing, and RNA interference, where a blasticidin resistance gene (such as bsr or BSD) is co-introduced with the gene of interest. This allows for rapid and efficient selection of successfully transfected or transduced cells. Due to its fast action and high potency, blasticidin S hydrochloride is preferred when quick selection is needed, typically within 2–10 days. It is also used in the generation of stable cell lines and in studies requiring long-term maintenance of transfected genetic elements. Careful titration is required as it can be toxic to certain cell types even at low concentrations.