| Description: |
Arthrobacter species are found in extreme environments, such as deep subsurface soils, arctic sea and radioactive waste tanks. Members of the Arthrobacter genus show a life cycle characterized by cell morphological changes, converting from rod to V-shaped and coccus forms, and back to rod shapes. The rod to coccus Arthrobacter morphogenesis has been involved in the ability to survive stresses of the bacterium. Arthrobacter aurescens (strain TC1) is an aerobic Gram-positive originally isolated from soil at a South Dakota spill site containing the herbicide atrazine. The genome of this bacterium comprises a single circular chromosome and two plasmids (pTC1 and pTC2) that encode for a large number of proteins involved in stress responses due to starvation, desiccation, ionizing radiation, oxygen radicals, and toxic chemicals. Its ability to survive is directly related to its genomic versatility, especially with respect to nitrogen metabolism and the ability to grow on polymeric sublayers that are not often used by many soil microbes. It has the ability to grow on a wide variety of carbon compounds and to catabolize a variety of xenobiotic compounds, such as glyphosate, methyl tert-butyl ether, 2,4-dichlorophenoxyacetate (2,4-D), nicotine, 4-nitrophenol, dimethylsilanediol, fluorene, phthalate, nitroglycerine and various s-triazine compounds. Due to their metabolic diversity, Arthrobacter species have been used in industrial applications and they are currently being used in the bioremediation of contaminated groundwater. Arthrobacter has the ability to survive continuously generated reactive oxygen radicals produced by its intense aerobic metabolism. This derives, in part, from 14 genes encoding oxidases that use molecular oxygen to metabolize amino groups. This is more than any other bacterium for which a genome sequence has been published. Arthrobacter aurescens TC1 is likely to sequester significant levels of manganese, which might be important for its resistance to oxidative stress (manganese-dependent dioxygenase). The genes for both the biosynthesis and catabolism of trehalose and glycogen are present in A. aurescens TC1, which is expected for an osmoprotectant that would be formed transiently and degraded when not needed. It also contains 14 cupin domain-containing proteins which are thought to be involved in stress responses, cell morphogenesis and development, cell wall structure, and desiccation tolerance. The high degree of genome duplication (genes involved in transcription, metabolism and other defense mechanism) may allow TC1 strain to rapidly adapt to changing environments. TC1 may have the ability to degrade plant-derived opines or other novel amino acid-derived compounds produced in the plant rhizosphere. It lacks the genes for flagella synthesis and chemotaxis. About 17% of TC1 genome (833 ORFs) is devoted to energy production. All three triazine hydrolase genes, trzN, atzB, and atzC, are located on pTC1 plasmid and nowhere else in the A. aurescens TC1 genome. A complete cluster of genes involved in the biodegradation of isopropylamine (ipu) was found on each of the two TC1 plasmids. They most likely allow A. aurescens TC1 to metabolize several s-triazines as a sole growth carbon and nitrogen source. ORFs involved in resistance to copper, arsenate, and cobalt-zinc-cadmium were found on pTC2 plasmid. |
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