Arthrobacter

Arthrobacter is a genus of bacteria that is commonly found in soil. All species in this genus are Gram positive obligate aerobes that are rods during exponential growth and cocci in their stationary phase.

Colonies of Arthrobacter have a greenish metalic center on mineral salts pyridone broth incubated at 20&degree; C. This genus is distinctive because of its unusual habit of "snapping division" in which the outer cell wall ruptures at a joint (hence it's name). Microbiologists refer to the type of cell division in which rods break into cocci as reversion. Under the microscope, these dividing cells appear as chevrons ("V" shapes). Other notable characteristics are that it can use pyridone as its sole carbon source, and that it's cocci are resistant to desication & starvation.

Life cycle

Induction phase (rods and cocci are mixed), Bacillary phase (motile rods predominate during exponential growth), Reversion phase (rods break into cocci) -> Induction...