<h3>Answer:<u><em>What organism is responsible for the cycling of nitrogen?</em></u></h3><h3><em><u /></em></h3><h3>Explanation:<u><em>Bacteria</em></u></h3><h3><u><em>Bacteria play a key role in the nitrogen cycle.</em></u></h3><h3><u><em>Some species of nitrogen-fixing bacteria are free-living in soil or water, while others are beneficial symbionts that live inside of plants.</em></u></h3><h3><em><u /></em></h3>