Question: bacterial cell walls are made rigid by the presence of
[{'answer': 'Peptidoglycan', 'provenance': [{'wikipedia_id': '24838', 'title': 'Peptidoglycan', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 13, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Peptidoglycan , also known as murein'}, {'provenance': [{'wikipedia_id': '24838', 'title': 'Peptidoglycan', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 742, 'bleu_score': 0.62470134638533, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12476422488726559119}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '24838', 'title': 'Peptidoglycan', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 0, 'bleu_score': 1.0, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12476422488726559119}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '4209093', 'title': 'Bacterial cell structure', 'section': 'Section::::Cell wall.\n', 'start_paragraph_id': 12, 'end_paragraph_id': 12, 'meta': {'evidence_span': ['Peptidoglycan is responsible for the rigidity of the bacterial cell wall and for the determination of cell shape. It is relatively porous and is not considered to be a permeability barrier for small substrates.', 'The bacterial cell wall differs from that of all other organisms by the presence of peptidoglycan which is located immediately outside of the cytoplasmic membrane. Peptidoglycan is made up of a polysaccharide backbone consisting of alternating N-Acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) residues in equal amounts. Peptidoglycan is responsible for the rigidity of the bacterial cell wall and for the determination of cell shape.', 'The bacterial cell wall differs from that of all other organisms by the presence of peptidoglycan']}}]}]