Question

Some bacteria live in the roots of plants like soybeans and peas.

Bacteria growing on plant roots.
What is the role of these bacteria in the nitrogen cycle?

to absorb nitrogen-containing compounds from the soil
to release free nitrogen into the atmosphere
to break down nitrogen-containing compounds in dead organisms
to convert free nitrogen into usable nitrogen

Answer 1

Answer: The symbiotic nitrogen-fixing bacteria invade the root hairs of host plants, where they multiply and stimulate formation of root nodules, enlargements of plant cells and bacteria in intimate association. Within the nodules the bacteria convert free nitrogen to ammonia, which the host plant utilizes for its development.

Answer 2

to conert free nitrogen into unstable nitrogen