<prompt> Antibiotic gramicidin S is derived from ?Bacillus brevisCl difficleS epidermidisStreptococcus bovis  <response>: Ans. isai.e., Bacillus brevisGramicidin-s is an antibiotic effective against some Gram positive and Gram negative bacteria as well as some fungi.It is a derivative of gramicidin, produced by the Gram positive bacterium Bacillus brevis. 