Antibiotics are commonly used drugs that can inhibit the growth of harmful bacteria. There are many kinds of antibiotics, except a few of which can be synthesized artificially, most of which are secreted by antibiotic bacteria through fermentation tanks. Antibacterial bacteria are mainly actinomycetes and some fungi and bacteria. The antibiotics they produce can inhibit the growth of some germs and kill some germs. For example, penicillin produced by Penicillium, streptomycin produced by Streptomyces, oxytetracycline produced by Geotrichum and polymyxin produced by Bacillus polymyxa can kill some harmful bacteria.