Membrane invaginations in bacteria and mitochondria: common features and evolutionary scenarios.

Nonphotosynthetic bacteria generally lack intracellular membranes (ICMs). However, large scale overproduction of membrane proteins in Escherichia coli can be accompanied by a massive proliferation of new ICMs in the cytoplasm. In some cases, like in the overexpression of the ATP synthase b subunit in E. coli, the morphology of these internal invaginations resembles that of the inner mitochondrial cristae. Moreover, the new ICMs have a higher content in cardiolipin than the bacterial inner and outer membranes. This review covers the features that seem to apply to membrane proliferation in bacteria and highlights the similarities with those behind the formation of the mitochondrial inner cristae.