Figure 9. Amino acid relations of the pea aphidAcyrthosiphon pisumand its symbiotic bacteriumBuchnera aphidicola. The schematic
shows hypothetical relations based on the annotation of amino acid biosynthesis genes in the two organisms.Buchneracells are located in the
cytoplasm of specialized aphid cells, known as bacteriocytes. EachBuchneracell is bound by three membranes, interpreted as the inner bacterial
membrane (brown), outer bacterial membrane (green), and a membrane of insect origin known as the symbiosomal membrane (purple). The
predicted biosynthesis (dark arrows) of essential amino acids (purple) and nonessential amino acids (green) and transport (light arrows) o