Scanning electron micrograph (SEM) of Micrococcus luteus, a Gram-positive to Gram-variable, nonmotile, Coccus, saprotrophic bacterium that belongs to the family Micrococcaceae. It is urease- and catalase-positive. An obligate aerobe, M. luteus is found in soil, dust, water and air, and as part of the normal flora of the mammalian skin. The bacterium also colonizes the human mouth, mucosae, oropharynx and upper respiratory tract. It was discovered by Sir Alexander Fleming before he discovered Penicillin in 1928. M. luteus forms bright yellow colonies on nutrient agar. It was sequenced in 2010 and has one of the smallest genomes of free-living actinobacteria sequenced to date.