Structural analysis of bacterial (Buchnera) and symbiosomal membranes in the pea aphid.

A: low magnification view of a bacteriocyte cell showing Buchnera cells, numerous mitochondria and the vesicular system within host-cell cytoplasm; B: enlarged view of Buchnera and mitochondria, showing the three membranes of the Buchnera symbiosome; C: higher magnification view of membrane organization, with the inner/outer double membrane of a mitochondrion (with matrix and cristae), and the triple membrane surrounding Buchnera; D: another view of Buchnera and adjacent mitochondrion multiple membranes; E: highest magnification view of membrane organization, showing the m1/m2/m3 triple membranes delineating Buchnera. All intermembrane distances (see Results) were measured at the scales indicated with Olympus Analysis® software; F: lower magnification view of older maternal bacteriocytes. In all figures, the following abbreviations are used: bcy: Buchnera cytoplasm, acy: aphid bacteriocyte cytoplasm, mt: mitochondria, mtmx: mitochondrial matrix, mtim: mitochondrial inner membrane, mtom: mitochondrial outer membrane, m1: Buchnera inner membrane, m2: Buchnera outer membrane, m3: symbiosomal membrane surrounding the Buchnera cells, Nu: nucleus, ssm: symbiosome (symbiosomal vesicle), iss: intrasymbiosomal space (extracellular to Buchnera), isvs: intrasymbiosomal vesicle, icvs: intracytoplasmic vesicle.