Genetically modified bacteria can be made to produce large quantities of useful substances such as insulin or vaccines or can be used in medical or industrial processes. Gene libraries can also be built up by storing the DNA in the microorganism for use in the future. However, genetically engineered pathogens pose a danger to the public and are strictly regulated. There are fears that genetically engineered pathogens may be used in biological warfare so genetic modification of pathogens is restricted to specialised military research facilities.The ethics of placing human DNA in microorganisms were initially an issue but now there is little objection in the light of the benefits of using microorganisms to produce pure medicines, enzymes and antibiotics.