This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Protein A of staph aureus is pa of bacterial ? \nSelect and explain. \nA. Genome, B. Cell wall, C. Limiting membrane, D. Plasmid', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. is \'b\' i.e., Cell wall Protein A is a cell wall component of many S aureus strains that binds to the Fc poion of IgG molecules except IgG3.The Fab poion of IgG bound to protein A is free to combine with a specific anigen. Protein a has become an impoant reagent in immunology and diagnostic laboratory technology; for example, protein A with attached lgG moleculaes directed against a specific bacterial antigen will agglutinate bacteria that have that antigen ("coagglutination").', 'role': 'assistant'}]