A broad-spectrum tetracycline antibiotic; inhibits growth of both Gram-positive and Gram-negative bacteria at a range of 0.1-100 μg/ml against A. aerogenes, D. pneumoniae, E. coli, K. pneumoniae, P. morganii, and several species of Hemophilus, Neisseria, Salmonella, and Staphylococcus; protects mice from infection by S. aureus (PD50s = 0.2-7.5 mg/kg for various strains), E. coli (PD50 = 3 mg/kg), and K. pneumoniae (PD50 = 75 mg/kg); an ionophore that is selective for calcium over sodium, potassium, magnesium, strontium, and barium