Query: NC_011833:31192 Buchnera aphidicola str. 5A (Acyrthosiphon pisum) chromosome,
Lineage: Buchnera aphidicola; Buchnera; Enterobacteriaceae; Enterobacteriales; Proteobacteria; Bacteria
General Information: This strain is found in the pea aphid, Acyrthosiphon pisum. Buchnera of A. pisum are the prime model of an obligate symbiosis. Aphid endosymbiont. Almost all aphids contain maternally transmitted bacteriocyte cells, which themselves contain bacteria called Buchnera. The aphids live on a restricted diet (plant sap), rich in carbohydrates, but poor in nitrogenous or other essential compounds. 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_005364:1133962 Mycoplasma mycoides subsp. mycoides SC str. PG1, complete genome
Lineage: Mycoplasma mycoides; Mycoplasma; Mycoplasmataceae; Mycoplasmatales; Tenericutes; Bacteria
General Information: Causative agent of contagious pleuropneumonia in livestock. This genus belongs to the class Mollicutes (phylum Tenericutes), a taxonomic group of small (0.3-0.8 micron diameter) monoderm bacteria characterized by the lack of cell walls, reduced genome sizes, and obligate parasitic lifestyles (Krieg et al., 2010). Over 120 obligate parasitic species found in a wide spectrum of hosts, including humans, animals, insects and plants. Infection typically proceeds through the attachment of bacteria to host cells via assorted adhesins or, in some species, through highly specialized surface protein appendages. In some cases, subsequent invasion of host cells results in a prolonged intracellular persistence that may cause lethality. These adaptive strategies are involved in host cell attachment and invasion, as well as immune evasion. Although mycoplasmas are dependent on their association with eukaryotic host tissue in nature, most can be cultivated axenically if their fastidious growth requirements are met. Nearly all mycoplasmas derive energy only from glycolytic pathways, whereas some can hydrolyze arginine. Assigned to the genus Mycoplasma by historic taxonomic precedent, organism in the Mycoplasma mycoides phylogenetic cluster are in fact more closely related to other genera in the Mollicutes (Krieg et al., 2010).