MICROBIOLOGY CHAPTER 21

Both ammonium (NH4+) and nitrate (NO3-) are assimilated by primary producers, but ammonium is the preferred form of nitrogen for fertilizers used in agriculture because __________.

Negatively charged nitrate seeps through too easily

Many nutrient cycles are coupled and changes in one cycle will affect another. This means that a change in the amount of carbon dioxide fixed is intimately affected by the amount of __________.

Nitrogen available in an ecosystem

A farmer wants to acidify his alkaline soils by adding elemental sulfur (S0), which will, under the right conditions, be oxidized to H2SO4 by chemolithotrophs. However, the weather report predicts heavy rains and possible localized flooding starting within in a few days and lasting for the next couple of weeks. Why should the farmer wait to apply the S0 to his fields until the soils are well-drained?

Potent greenhouse gas that is a product of denitrification.

What would the result be when a soil is supplemented with S0?

Soil acidification due to chemolithotrophs

Abiotic oxidation of Fe2+ requires oxygen and occurs rapidly when the pH is near 7.

True

In the natural carbon cycle, carbon dioxide is returned to the atmosphere by the respiration of animals and chemoorganotrophic microorganisms. True or false?

True

Most chemolithotrophic bacteria that oxidize sulfur are aerobes.

True

Why would using nitrogenous fertilizer near a body of water affect the organisms in the body of water?

When runoff enters the body of water, the nitrogen level significantly increases, which increases the activity of the microorganism there and upsets the balance of the ecosystem.

Denitrification contributes to global warming by __________.

Destroying ozone

Geobacter sulfurreducens uses its pili to form direct connections with insoluble ferric iron particles. As the organism carries out respiration, the Fe3+ is acting as a(n) __________.

Electron acceptor

Sulfate reduction (SO42- → H2S) occurs only where organic material is abundant because __________.

Electrons from organic compounds are necessary for this reaction

Denitrification of fertilizer can result in harmful algal blooms.

False

In anoxic environments, organic compounds are cycled back to carbon dioxide and methane by __________.

Fermentation

Agricultural application of nitrogen fertilizer

Increases global warming by increasing the production of nitrous oxide (N2O) by denitrification in agricultural soils.

A process where different microbial taxa work in cooperation to degrade a compound that neither can perform entirely on their own is called...

Synthrophy

Nitrification and anammox both...

oxidize ammonia, but nitrification uses O2 as an electron acceptor and anammox uses NO2-.