SUMMARY: Species of the genus have a guanine + cytosine (GC) content in DNA within the range 30·7-36·4 moles %. All the Gram-positive cocci so far designated as micrococci and sarcinas which produce acid from glucose when grown under anaerobic or aerobic conditions and have a GC content in DNA within this range should be also classified as . On the other hand species of the genus have a GC content in DNA within the range 66·3-73·3%. All the Gram-positive cocci hitherto designated as sarcinas and staphylococci which do not produce acid from glucose under aerobic or anaerobic conditions or only aerobically and which have a GC content in DNA within this range, should be also classified as . The range of GC content as outlined is approximate; it will be made more accurate (perhaps a little broader) when more data are available on the DNA base composition of the species belonging to the family Micrococcaceae.

On the basis of their DNA base composition the strains belonging to the genus are divided into three groups: group 1 (70·8-73·3 moles % GC); group 2 (67·5-69·5 moles % GC); group 3 (66·3-67·0 moles % GC). Similarly the strains belonging to the genus have been divided into three groups: group 5 (36·4 moles % GC); group 6 (33·3-34·2 moles % GC); group 7 (30·7-32·7 moles % GC). Strains within each group are believed to be phylogenetically related. When subjected to Adansonian analysis, the strains of the individual groups were clustered into subgroups. Each subgroup comprised the strains with approximately the same DNA base composition and a high % similarity of physiological and biochemical characters. Strains clustered into subgroups are believed to be genetically closely related, some may be identical. The following subgroups are suggested: micrococcus subgroups 1a, 1b, 2a, 2b, 2c, 3a, 3b; staphylococcus subgroups 5a, 6a, 7a. Arabic numerals refer to the designation of the group.

The classification of micrococci presented in this paper is substantially the same as that of Baird-Parker (1965). The authors are of the same opinion as Baird-Parker (1965) that should be reclassified with the Gram-negative genera.


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