earliest years of antibiotic discovery the antibiotics being discovered were naturally produced antibiotics and were either produced by fungi, such as the antibiotic penicillin, or by soil bacteria, which can produce antibiotics including streptomycin and tetracycline. Microorganisms used in fermentation are rarely identical to the wild type. This is because species are often genetically modified to yield the maximum amounts of antibiotics. Mutation is often used, and is encouraged by introducing mutagens such as ultraviolet radiation, x-rays or certain chemicals. Selection and further reproduction of the higher yielding strains over many generations can raise yields by 20-fold or more. Another technique used to increase yields is gene amplification, where copies of genes coding for enzymes involved in the antibiotic production can be inserted back into a cell, via vectors such as plasmids. This process must be closely linked with retesting of antibiotic production. Some antibiotics are produced naturally by fungi. These include the cephalosporin producing Acremonium chrysogenum. Geldanamycin is produced by Streptomyces hygroscopicus. Erythromycin is produced by what was called Streptomyces erythreus and is now known as Saccharopolyspora erythraea. Streptomycin is produced by Streptomyces griseus. Tetracycline is produced by Streptomyces aureofaciens Vancomycin is produced by Streptomyces orientalis, now known as Amycolatopsis orientalis. Advancements Penicillin was the first of the antibiotics to be discovered. After the discovery there was the issue of taking the raw naturally produced penicillin and developing a method so that wide-scale production of a clinically significant antibiotic could occur. Over the course of many years a team led by Florey and Chain and based in Oxford was able to successfully purify, concentrate, and produce the antibiotic. Advances in scientific technology have not always led to better conditions for the production of antibiotics. Since 1987 there have been no new classes of antibiotics discovered for industrial production and widespread usage. However new developments in genomic sequencing and technology have led to improvements and discovery in the field of antibiotic production. Genomic engineering of antibiotic gene clusters has already been shown to lead to an increase in production of different antibiotics. Antibiotic production and delivery method Antibiotics do not render themselves fully functional and deliverable simply by being produced. Often modifications must be made to the antibiotics so that maximum efficiency is attained. Post-production modifications include making antibiotics aerosolized so as to bypass doing unnecessary damage to bacteria located in other parts of the body and instead going directly