These are Gram-positive, non-sporing non-acid fast cocci. They generally occur in tetrads (groups of four) or clusters and are not motile. They are generally aerobes and produce catalase. Carotenoid pigments are produced by most species. Most will grow on bacteriological media such as nutrient agar at 37°C except some psychrotropic and halophyllic species which require cooler temperatures or 5%NaCl. There are only two genera in this family; Arthrobacter and Micrococcus. The genera Staphylococcus and Planococcus which were once considered part of this family are now excluded, due to marked differences in DNA base composition, cell wall, fatty acids and other compositions.

Genera

Arthrobacter: This includes two 'groups of species', known as the A. globiformis / A.citreus group and the A. nicotianae group, based on differences in cell wall structure. They are important soil organisms, often being the numerically largest numbers of isolates on aerobic primary isolation media.

Micrococcus: This genus consists of nine species, of which M.luteus (previously known as M. lysodeikticus), M. lylae, M. roseus are most studied. M. agilis differs from other species in being motile, psychrophilic and producing beta-galactosidase. M. kristinae can ferment glucose anaerobically and M. halobius requires at least 5% NaCl for growth.

Species Profiles

M. luteus

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