Query: NC_017256:30192 Buchnera aphidicola str. Ak (Acyrthosiphon kondoi) chromosome,
Lineage: Buchnera aphidicola; Buchnera; Enterobacteriaceae; Enterobacteriales; Proteobacteria; Bacteria
General Information: It is believed that the Buchnera provide the essential nutrients the host lacks. Besides a nutritional co-dependence, due to a co-existence of millions of years, Buchnera have lost the ability to produce cell surface components such as lipopolysaccharides. This makes for an obligate endosymbiont relationship between host and Buchnera. Buchnera are prokaryotic cells which belong to the gamma-Proteobacteria, closely related to the Enterobacteriaceae family. Phylogenetic studies using 16S rRNA indicate that the symbiotic relationship was established around 200-250 million years ago. Since Buchnera are closely related to Escherichia coli and Haemophilus influenzae, comparative genomic studies can shed light on the evolutionary mechanisms of intracellular endosymbiosis as well as the different underlying molecular basis between organisms with parasitic behavior and symbionts.
Subject: NC_019771:2945719 Anabaena cylindrica PCC 7122, complete genome
Lineage: Anabaena cylindrica; Anabaena; Nostocaceae; Nostocales; Cyanobacteria; Bacteria
General Information: Country: United Kingdom; Environment: Ponds; Isolation: Water, most likely pond, Cambridge, UK, 1939; Temp: Mesophile. They form long filaments and can be found worldwide in various aquatic environments as well as some terrestrial ones. These bacteria can form a variety of differentiated cell types, including spore-like cells (akinetes), small motile filaments (hormongia) and most importantly, heterocysts that are nitrogen-producing cells. The heterocyst produces multiple layers outside of its cell wall, shuts down photosystem II in order to inhibit oxygenic photosynthesis and ramps up metabolism in order to use up the oxygen present. Heterocysts donate fixed nitrogen compounds as amino acids to neighboring cells and in return receive a photosynthetically produced carbon source such as sucrose. These organisms produce toxic blooms in aquatic environments that are harmful or fatal to animals and humans due to the various cyanotoxins they produce.