MicrobeWorld

Biosphere in a Bottle - What causes the red, orange, green, white and black colors?

Red and orange patches are purple photosynthetic bacteria. Green patches at or near the surface of the mud are cyanobacteria /sigh-an-o-back-tear-e-ah/ and algae. Olive-green patches in the middle or lower part of the jar are green sulfer bacteria. The black patches are iron sulfide, a chemical formed by certain bacteria.