Micrococcaceae

Micrococcaceae is a family of Gram-positive, non-spore-forming bacteria within the order Micrococcales and the class Actinobacteria. Members are typically aerobic or facultatively anaerobic cocci or coccobacilli that occur singly, in pairs, in tetrads, or in irregular clusters. They are catalase-positive and nonmotile, and they generally have a relatively high G+C content in their DNA. The family includes several clinically and ecologically important genera.

Ecology and significance: Micrococcaceae are widespread in nature, found in soil, water, dust, and on human and animal skin and mucous membranes. Many species are ordinary environmental inhabitants or commensals, but several are opportunistic pathogens, especially in immunocompromised individuals. The genus Micrococcus (for example Micrococcus luteus) is often environmental or harmless on the skin, while other genera such as Kocuria, Rothia, and Arthrobacter include species that have been isolated from clinical infections, including bacteremia, endocarditis, or pneumonia, though these infections are relatively uncommon.

Laboratory and taxonomy: Laboratory identification typically notes catalase-positivity and a tendency toward pigmented colonies in some species (notably Micrococcus luteus). Differentiation from other Gram-positive cocci relies on biochemical testing and molecular methods. Taxonomy within Micrococcaceae has undergone revisions with advances in 16S rRNA sequencing and whole-genome analyses, leading to reclassification of some species into related genera such as Kocuria or Arthrobacter. The composition and boundaries of the family remain subject to update as new data emerge.

See also: Micrococcales, Micrococcus, Kocuria, Rothia, Arthrobacter.