Microbiology and Nitrogen Cycle

These bacteria are found in the alimentary canal of human beings. They keep a check on the growth of harmful putrefying bacteria in the gut of the human beings. They also release vitamins K and B₁₂ which are necessary for blood components. In return human host provides shelter and food for these bacteria. So, they are symbiotic bacteria.

Yes, it is the correct answer as the microbes reside in the root nodules of leguminous plants. They can fix nitrogen from the air into soil and increase the soil fertility.

This is the correct option. The root nodules of millet do not have nitrogen-fixing bacteria called rhizobium bacteria. It is a non-leguminous plant.

Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization.

The enormous energy of lightning breaks nitrogen molecules and enables their atoms to combine with oxygen in the air, forming nitrogen oxides. These dissolve in rain, forming nitrates, that are carried to the earth.

Rhizobium is a soil bacterium that fixes nitrogen (diazotrophs) after becoming established inside the root nodules of legumes (Fabaceae).

Denitrifying bacteria convert nitrates and other complex nitrogen compounds back into nitrogen gas (N2), completing the nitrogen cycle. This process returns nitrogen to the atmosphere in its elemental form. Fungi, viruses, and algae do not play this specific role in nitrogen cycling.

Plants that contribute to nitrogen fixation include the legume family – Fabaceae – with taxa such as kudzu, clovers, soybeans, alfalfa, lupines, peanuts, and rooibos. They contain symbiotic bacteria called rhizobia within nodules in their root systems, producing nitrogen compounds that help the plant to grow and compete with other plants.

Each bacterial cell contains a single chromosome, which is not enclosed in a nuclear membrane.

Endospore formation takes place in bacteria.

Digitaria belongs to the family Poaceae. Digitaria is a species of grass known by the common name hairy crabgrass or large crabgrass which has root nodules with nitrogen fixing bacteria.

The main driving factor of the oxygen cycle is Photosynthesis, which is responsible for the modern Earth's atmosphere and life on earth.

Ammonia-oxidising bacteria are chemolithotrophic bacteria that get carbon for biosynthesis from carbon dioxide.

Green non-sulphur bacteria are photoheterotrophs. They use light for energy and use organic compounds to satisfy their carbon needs.

The above mentioned medium would act as a defined enrichment medium for the growth of Thiobacillus thiooxidans. It is chemically defined and it contains elemental sulphur as carbon source, enriching it for the growth of Thiobacillus thiooxidans.