Question: which bacteria helps nitrogen fixation in the soil
[{'answer': 'Azotobacter', 'provenance': [{'wikipedia_id': '21989', 'title': 'Nitrogen fixation', 'start_paragraph_id': 3, 'start_character': 139, 'end_paragraph_id': 3, 'end_character': 150, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]