F in selenite F broth is faeces,because it is mostly used for the isolation of salmonelle shigella from faecal specimens.Selenite F broth inhibit the growth of coliforms for 8 to 12 hrs.So subculture...
Simple. When you say 'F', I hope you mean the one that you get from a teacher for bad work. If you want an F to become F-, do one of the following: 1) Go to another school with stricter teachers OR2)...