Arthrobacter is a common genus of soil bacteria. All species in this genus are Gram-positive, obligate aerobes. Like many soil bacteria, this genus is metabolically versatile, producing many different enzymes allowing it to grow on a wide range of substrates. The cells can be quite tough and resist desiccation and starvation. Arthrobacter species have been isolated a few times from patients with immunodeficiencies but most strains do not appear to be pathogenic. A distinctive feature of this genus is that the shape of the cells changes during the growth cycle, typically forming rods during exponential growth and cocci in the stationary phase:

Type species: