Abstract
Staphylococcus sciuri is considered to be one of the most ancestral species in the natura history of the Staphylococcus genus that consists of 48 validly described species. It belongs to the basal group of oxidase-positive and novobiocin-resistant staphylococci that diverged from macrococci approximately 250 million years ago. Contrary to other groups, the S. sciuri species group has not developed host-specific colonization strategies. In this current study, the genome analysis of S. sciuri ATCC 29059 provided the first genetic basis for atypical traits that would support the switch between the free-living style and the infective state in animals and humans. From among the most remarkable features, it was noticed in this extensive study that there were a number of phosphoenolpyruvate:carbohydrate phosphotransferase systems (PTS), almost twice as many as any other staphylococci, and the co-occurrence of mevalonate and non-mevalonate pathways for isoprenoid synthesis. The sequenced strain was devoid of the main virulence factors present in Staphylococcus aureus, although it exhibited numerous heme and iron acquisition systems, as well as crt and aldH genes necessary for gold pigment synthesis. The sensing and signaling networks, exemplified by a large and typical repertoire of two-component regulatory systems and a complete panel of master regulators, such as agr, rex, mgrA, rot, sarA and sarR genes, depicted the background in which S. aureus virulence genes were later acquired. An additional sigma factor, a distinct set of electron transducer elements and many gene operons similar to those found in Bacillus spp. would constitute the most visible remnant links with Bacillaceae organisms.