The name 'antibiotic' was first given to the drugs that exhibit 'antibiosis' (meaning 'against life'), by Selman Waksman in 1942. After Vincenzo Tiberio discovered a mold (penicillium) in a well that displayed antibacterial, it led others to find the reasoning behind this. However, it was Alexander Fleming's (above) observations of fungus working against bacteria and concluded that it was due to the antibacterial compound, Penicillin.
The ionophores were first recognized as being a separate class with the publication of the structure for monensin in 1967. Several members of the group have found commercial application as anticoccidials in poultry farming and as growth promoters for cattle, pigs and chickens.