An amended description of Micrococcus luteus (Schroeter 1872) Cohn 1872, at present a broad-based species characterized primarily on negative charact eristics, is proposed on the basis of a taxonomic analysis of 30 strains. CCM 169 (= ATCC 4698) is designated a' s the neotype strain of M . luteus.A large number of species of aerobic, catalase-positive, yellow-pigmented micrococci have been described, but their incomplete characterization has hindered their classification. Some of them are known as Micrococcus luteus, M. f l a w s , M. lysodeikticus, Sarcina lutea, and S. flava. At present only two of these are generally accepted: M. luteus and M. varians (13,21).Although M. luteus is the type species of the genus Micrococcus, it is not sufficiently defined. At present it is a broad-based species characterized almost solely on negative characters (3, 19). The purpose of this paper is t o give an amended characterization of M. luteus.
MATERIALS AND METHODSBacterial strains. Thirty-one strains of aerobic, yellow-pigmented micrococci were investigated, all from the Czechoslovak Collection of Microorganisms, Brno (Table 1). A number of strains originally identified as nonpigmented strains of M. luteus were initially included among the strains studied. However, a detailed examination of these organisms (including deoxyribonucleic acid [DNA] base composition and type of peptidoglycan in the cell wall) showed that they were coagulase-negative staphylococci. Nonpigmented strains of M. luteus are rarely encountered.Media and methods. The strains were maintained on nutrient agar at 4 C. For morphological, cultural, and biochemical studies, an incubation temperature of 30 C was used.The methods used were described previously (19,20,21).
RESULTS
Morphology.All of the strains studied were gram-positive cocci measuring 0.9 t o 1.8 pm in diameter and arranged in tetrads and in irregular clumps of tetrads. Strains CCM 248, 337, 1674, and 2494 formed packets and irregular clusters of packets. These strains also produced the largest cells (1.5 to 1.8 p m ) of all of those studied. None of the strains was motile or produced spores.Cultural characteristics. Colonies of all of the strains were circular, convex, and smooth, with either a glistening or a dull surface. Tetrad-and packet-forming strains produced matted colonies. All of the strains formed a yellow or greenish-yellow , water-insoluble pigment on most solid media tested. Five strains (CCM 247, 622, 851, 852, and 853) produced also a yellow, water-insoluble pigment and a violet, water-soluble pigment when grown on yeastglucose agar. Strain CCM 2506 produced a brown extracellular pigment on nutrient agar. In nutrient broth all strains produced a slight turbidity and sediment.Biochemical characteristics. The biochemical characteristics of the 30 strains regarded here as belonging to M. lutezis are given in Table 2. The 30 strains formed a homogeneous group with an average of 72.4% guanine plus cytosine (GC) in the DNA. All of the strains hydrolyzed gelatin, were sensitive t ...
