Members of the genus Staphylococcus are gram positive cocci of size 0.5-1.5 um in diameter. They occur in singles, pairs, tetrads, short chains and irregular grape like cluster. They are nonmotile and nonspore- forming. Most species are catalase positive and are facultative anaerobes, grows better under aerobic than anaerobic conditions. The anaerobic species Staphylococcus saccharolyticus and Staphylococcus aureus subsp. anaerobius are exceptions.
They are susceptible to furazolidone (100ug furazolidone disk) and resistant to low levels of bacitracin (0.04 units bacitracin disk). They are susceptible to lysis by Lysostaphin and are relatively resistant to lysis by lysozyme. The cell wall contains peptidoglycan and teichoic acid. The diamino acid present in the peptidoglycan is L-lysine, except in ancient species S. succinus which is meso- diaminopimelic acid. The inter peptide bridge of the peptidoglycan consists of oligoglycine that are susceptible to the action of lysostaphin. Depending on the particular species, some glycine residues may be substituted by L- serine or L- alanine. The teichoic acids of Staphylococcus are either of the poly (polyolphosphate), poly (polyglycerolphosohate-glycosylphosphate) or poly (polyglycosylphosphate) class.
Glycerol or ribitol or both occur as atypical components of poly (polyolphosphate) teichoic acids. Species contains either a – and b- type cytochoromes or a-, b-, and c- type cytochromes. Staphylococci unsaturated polyisoprenoid side chains in their menaquinones. The majority isoprenologues are MK-6, MK-7 or MK-8.
G+C content of DNA is 30-40 mol%.
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