One of the most productive sources of antibiotics has been the genus Streptomyces, an actinomycete of which there are many species and from which over 500 antibiotics have been identified. More than 50 of these have found practical applications including streptomycin. chloramphenicol and the tetracyclines. Streptomycin was dis- covered soon after penicillin(which is produced by a fungus. see section 3.1.6). It proved almost as dramatically successful, increasing the range of pathogens that could be treated. For example, unlike penicillin, it is active against the tuberculosis bacillus. Bacillus species have also proved fruitful, such as Bacillus brevis which produces gramicidin