Foil cap or Algae and cyanoba Purple nonsulfur bacteri supplemented Patches of purple sulfur or with organIc green sulfur bacteria nutrients and Anoxic decomposition and sulfate reduction H2s Figure 14.5 The Winogradsky column (a) Schematic view of a typical column. The column is placed so as to receive sub- dued sunlight. Chemoorganotrophic bacteria grow through out the column, aerobes and microaerophiles in the upper region ns, anaero obes in the zones containing H,S. Anoxic composition leading to sulfate reduction creates the gradi ent of H S Green and purple sulfur bacteria stratify according to their tolerance for H,S(b) Photo of Winogradsky columns that have remained anoxic up to the top where blooms of three different phototrophic bacteria have occurred in the lud and up into the water column. Left to right: Thiospirillum jenense, Chromatium oken, and Chlorobium limicola