The conversion of nitrate to nitrogen gas is achieved by

A) denitrifying bacteria.
B) leguminous bacteria.
C) nitrogen-fixing bacteria.
D) nitrate-producing fungi.
E) nitrite-producing fungi.

Denitrifying bacteria are responsible for converting nitrate to nitrogen gas. They do so through the process of denitrification, in which they use nitrate as an electron acceptor and reduce it to nitrogen gas. This process occurs in both natural and engineered systems where there is a lack of oxygen, such as in wetlands or wastewater treatment plants. Nitrogen-fixing bacteria and leguminous bacteria are responsible for converting nitrogen gas into usable forms of nitrogen such as ammonia or nitrates. Nitrate-producing and nitrite-producing fungi are not involved in the conversion of nitrate to nitrogen gas.