Bacteria and yeast. Coloured scanning electron micrograph (SEM) of bacteria (purple) and yeast. In many environments, bacteria and fungi coexist and interact. Furthermore, these bacterial-fungal interactions often have important ramifications for the biology of the interacting partners. In humans this coexistence in the human microbiome in health and during disease is of major research interest. Magnification: x6000 when printed at 10 centimetres high.