Editing Chloroplast (section)

=== Intermembrane space and peptidoglycan wall ===
[[File:Glaucocystis sp.jpg|thumb|Instead of an intermembrane space, [[glaucophyte algae]] have a [[peptidoglycan wall]] between their inner and outer chloroplast membranes.]]

Usually, a thin intermembrane space about 10–20 [[nanometers]] thick exists between the outer and inner chloroplast membranes.<ref name="Burgess-1989a">{{cite book|last=Burgess|first=Jeremy | name-list-style=vanc |title=An introduction to plant cell development|year=1989|publisher=Cambridge university press|location=Cambridge|isbn=0-521-31611-1|page=46|url=https://books.google.com/books?id=r808AAAAIAAJ&pg=PA46|edition=Pbk.}}</ref>

[[Glaucophyte algal]] chloroplasts have a [[peptidoglycan]] layer between the chloroplast membranes. It corresponds to the [[peptidoglycan cell wall]] of their [[cyanobacterial]] ancestors, which is located between their two cell membranes. These chloroplasts are called ''muroplasts'' (from Latin ''"mura"'', meaning "wall"). Other chloroplasts were assumed to have lost the cyanobacterial wall, leaving an intermembrane space between the two chloroplast envelope membranes,<ref name="Wise-2006b" /> but has since been found also in moss, lycophytes and ferns.<ref>[https://academic.oup.com/plphys/article/190/1/165/6574362 Plant peptidoglycan precursor biosynthesis: Conservation between moss chloroplasts and Gram-negative bacteria]</ref>