Used primarily as an antibiotic in microbiology and molecular biology, especially in cell culture and bacterial selection. Commonly added to growth media to select for bacteria that have been genetically modified with resistance genes, such as in plasmid transformations. Effective against a range of Gram-negative bacteria, including Pseudomonas aeruginosa. Often used in place of ampicillin when greater stability or broader spectrum activity is needed, particularly in sensitive strains. Also used in tissue culture to prevent bacterial contamination due to its reduced toxicity to mammalian cells at working concentrations. Suitable for plant cell culture.