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A Microbial Biorealm page on the genus Azoarcus

The phylogenic tree demonstrating the relationship of the beta-proteobacteria species Azoarcus evansii and Thauera aromatica, both of which share similar metabolic characteristics.


Higher order taxa:

Bacteria; Proteobacteria; Betaproteobacteria; Rhodocyclales; Rhodocyclaceae; Azoarcus

NCBI: Taxonomy Genome

Description and Significance

Azoarcus evansii is a species of proteobacteria; rod-shaped cells with polar flagella, which is associated with plants. This species is notable because of its interesting system of metabolic pathways. Because it is an aerobic aromatic bacterium, it is useful to scientists working to learn more about the enzymes utilized in the metabolism process.

Cell Structure and Metabolism

Azoarcus evansii 's mode of metabolism has been closely scrutinized by scientists who discovered that many of the normal bacterial pathways were not in evidence in this organism. Two independent catabolic pathways function to convert benzoate to benzoyl-CoA. This process is followed by an attack by an oxygenase, and concludes with a non-oxygenolytic fission of the ring. Proteins involved in metabolism number more than 150. Studies have been done on a number of the enzymes and proteins associated with the metabolic processes, in order to better understand and even put to use Azoarcus evansii's mode of generating energy. The morphology of the cells are rod-shaped with rounded ends, which are 1.5 - 3 microns long and 0.6 - 0.8 microns wide. Each cell is motile by way of a single flagellum, located subpolarly.


Data gathered from cultured Azoarcus evansii shows that this species grows optimally at 37ºC with a pH of 7.8.


Anders, Hans-Joachim et al. Taxonomic position of aromatic-degrading denitrifying pseudomonad strains K 172 and KB 740 and Their Description as New Members of the Genera Thauera, as Thauera aromatica sp. nov., and Azoarcus, Azoarcus evansii sp. nov., Respectively, Members of the Beta-Subclass of Proteobacteria. International Journal of Systematic Bacteriology April 1995. 327-333.

Mohamed, Mel-S. et al. Aerobic metabolism of phenylacetic acids in Azoarcus evansii. Arch Microbiology vol 178(3) September 2002. 180-192.

Mohamed, Magdy El-Said et al. Reinvestigation of a New Type of Aerobic Benzoate Metabolism in the Proteobacterium Azoarcus evansii. Journal of Bacteriology vol 183(6) March 2001. 1899-1908.