This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Staphylococci, Subject name: Microbiology
[{'content': 'Protein A of staph aureus is part of bacterial? \nSelect and explain. \nA. Genome, B. Cell wall, C. Limiting membrane, D. Plasmid', 'role': 'user'}, {'content': 'Answer: B \nExplanation: ANSWER: (B) Cell wallREF: Jawetz Microbiology, 24th Ed, Ch. 20Protein A is a cell wall component of many S aureus strains that binds to the Fc portion of IgG molecules except IgG3. The Fab portion of IgG bound to protein A is free to combine with a specific antigen. Protein A has become an important reagent in immunology and diagnostic laboratory technology; for example, protein A with attached IgG molecules directed against a specific bacterial antigen will agglutinate bacteria that have that antigen (\'\'coagglutination").Some S aureus strains have capsules, which inhibit phagocytosis by polymorphonuclear leukocytes unless specific antibodies are present. Most strains of S aureus have coagulase, or clumping factor, on the cell wall surface; coagulase binds nonenzymatically to fibrinogen, yielding aggregation of the bacteria.', 'role': 'assistant'}]