Complete Genome Sequence ofMacrococcus caseolyticusStrain JSCS5402, Reflecting the Ancestral Genome of the Human-Pathogenic Staphylococci

We isolated the methicillin-resistantMacrococcus caseolyticusstrain JCSC5402 from animal meat in a supermarket and determined its whole-genome nucleotide sequence. This is the first report on the genome analysis of a macrococcal species that is evolutionarily closely related to the human pathogensStaphylococcus aureusandBacillus anthracis. The essential biological pathways ofM. caseolyticusare similar to those of staphylococci. However, the species has a small chromosome (2.1 MB) and lacks many sugar and amino acid metabolism pathways and a plethora of virulence genes that are present inS. aureus. On the other hand,M. caseolyticuspossesses a series of oxidative phosphorylation machineries that are closely related to those in the familyBacillaceae. We also discovered a probable primordial form of aMacrococcusmethicillin resistance gene complex,mecIRAm, on one of the eight plasmids harbored by theM. caseolyticusstrain. This is the first finding of a plasmid-encoding methicillin resistance gene.Macrococcusis considered to reflect the genome of ancestral bacteria before the speciation of staphylococcal species and may be closely associated with the origin of the methicillin resistance gene complex of the notorious human pathogen methicillin-resistantS. aureus.