Simplify the following text for a Grade 10 native English-speaking person.
Original: These bacteria have the nitrogenase enzyme that combines gaseous nitrogen with hydrogen to produce ammonia , which is then further converted by the bacteria to make their own organic compounds .
Simplified: Most nitrogen fixation is done by micro-organisms called bacteria . These bacteria have an enzyme that combines N2 with hydrogen gas ( H2 ) to make ammonia ( NH3 ) .