Delimiting the genus Staphylococcus through description of Macrococcus caseolyticus gen. nov., comb. nov. and Macrococcus equipercicus sp. nov., Macrococcus bovicus sp. nov. and Macrococcus carouselicus sp. nov.

Four species of the newly proposed genus Macrococcus, namely Macrococcus caseolyticus gen. nov., comb, nov. (formerly Staphylococcus caseolyticus Schleifer, Kilpper-Balz, Fischer, Faller and Endl 1982, 19(VP)), Macrococcus equipercicus sp. nov., Macrococcus bovicus sp. nov. and Macrococcus carouselicus sp. nov., are described on the basis of a phylogenetic analysis comparing 16S rRNA sequences, DNA-DNA liquid hybridization, DNA base composition, normalized ribotype patterns, macrorestriction pattern analysis and estimation of genome size using PFGE, cell wall composition, phenotypic characteristics and plasmid profiles. Compared with their closest relatives, members of the genus Staphylococcus, these organisms demonstrated significantly lower 16S rRNA sequence similarities (93.4-95.3 %), higher DNA G+C content (38-45 mol%), absence of cell wall teichoic acids (with the possible exception of M. caseolyticus), unique ribotype pattern types and macrorestriction patterns, smaller genome size (approx. 1500-1800 kb) and generally larger Gram-stained cell size (1.1-2.5 mu m in diameter). Macrococci can be distinguished from most species of staphylococci (except Staphylococcus sciuri, Staphylococcus vitulus and Staphylococcus lentus) by their oxidase activity. The four Macrococcus species can be distinguished from one another on the basis of DNA-DNA hybridization, ribotype pattern types, macrorestriction patterns and their phenotypic properties, including colony morphology, cell morphology, haemolysins, Staph Latex agglutination, acid production from a variety of carbohydrates, acetoin production, nitrate reduction, aesculin hydrolysis, and DNase and urease activities. The type species is M. equipercicus. The type strains of M. equipercicus, M. caseolyticus, M. bovicus and M. carouselicus are ATCC 51831(T) (= DD 9350(T)), ATCC 13548(T) (= TDD 4508(T)) (Schleifer et al. 1982), ATCC 51825(T) (= DD 4516(T)) and ATCC 51828(T) (= DD 9348(T)), respectively.