The prokaryotic host cell outer membrane is the selectively permeable membrane which separates the prokaryotic periplasm from its surroundings in prokaryotes with 2 membranes. Traditionally only Gram-negative bacteria were thought of as having an outer membrane, but recent work has shown some Actinobacteria, including Mycobacterium tuberculosis, as well as at least 1 archaea (Ignicoccus hospitalis) have a cell outer membrane.

› Cellular component

› Host cell outer membrane

› host cell plasma membrane [ GO:0020002 ]