Selecting a Fly fishing rod free of charge post thanks to ArticleCity. com Fishing tipsHowever, it is diagnosed that sure micro organism are the maincause of spoilage see phase 5. 3. Different peptone richsubstrates containing ferric citrate have been used for detectionof H2S producing bacteria such as Shewanellaputrefaciens, which might be seen as black colonies due toprecipitation of FeS Levin, 1968; Gram et al. , 1987. Ambient spoilage is always brought on by members of Vibrionaceae thatalso will form black colonies on an iron agar to which an organicsulphur source is added e. g.