Bacteria that convert nitrogen gas into ammonia are:
a. Nitrifying bacteria
b. Nitrogenous
c. Nitrogen fixers
d. Nitrification bacteria

Verified step by step guidance

1. Understand the process described: converting nitrogen gas (N\_2) into ammonia (NH\_3) is a key step in the nitrogen cycle called nitrogen fixation.
2. Recall that nitrogen fixation is performed by specific bacteria that possess the enzyme nitrogenase, which allows them to break the strong triple bond in N\_2 and convert it into ammonia.
3. Identify the term used for bacteria that perform nitrogen fixation. These bacteria are commonly known as 'nitrogen fixers'.
4. Review the answer choices and match the correct term: 'nitrifying bacteria' are involved in converting ammonia to nitrites and nitrates, not nitrogen gas to ammonia; 'nitrogenous' is not a standard term for bacteria; 'nitrification bacteria' is another term for nitrifying bacteria.
5. Conclude that the bacteria converting nitrogen gas into ammonia are called 'nitrogen fixers', which corresponds to option c.

Key Concepts

Nitrogen Fixation

Nitrogen fixation is the biological process where certain bacteria convert atmospheric nitrogen gas (N2) into ammonia (NH3), making nitrogen available for plant use. This process is essential for incorporating inert nitrogen into the ecosystem.

Nitrogen-Fixing Bacteria

Nitrogen-fixing bacteria, such as Rhizobium and Azotobacter, possess the enzyme nitrogenase that enables them to reduce nitrogen gas to ammonia. These bacteria can live freely in soil or symbiotically within plant roots.

Nitrification

Nitrification is a separate microbial process where ammonia is oxidized to nitrites and then nitrates by nitrifying bacteria. This process does not convert nitrogen gas to ammonia but rather transforms ammonia into forms usable by plants.