Mastering Micro Chapter 21

destroying ozone

Denitrification contributes to global warming by __________.

False

Denitrification of fertilizer can result in harmful algal blooms.

Methylmercury accumulates in animal muscle and is biomagnified in the food chain.

Some microbial transformations of mercury yield more toxic forms of mercury, including the most toxic form, methylmercury (CH3Hg+). Which of the following properties of methylmercury in an aquatic ecosystem would be most problematic for humans?

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.

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

electron acceptor

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) __________.

sulfate-reducing bacteria

H2S that these newly described organisms use is at the highest concentration in anoxic marine habitats because ___________ produce it as an end product of anaerobic respiration, oxidizing H2 or small organic compounds with sulfate as the terminal electron acceptor

nitrogen available in the ecosystem

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 __________.

ammonification

Many organisms release ammonium (NH4+) from degradation of nitrogen-containing organic materials. This process is referred to as

True

Most chemolithotrophic bacteria that oxidize sulfur are aerobes.

photolithotrophs; chemolithotrophs

New organic compounds are produced from inorganic substrates by ___________ (such as plants) and ___________

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

Nitrification and anammox both

potent greenhouse gas that is a product of denitrification.

Nitrous oxide (N2O) is a _________

nitrifiers

Rates of NH3 oxidation in nature are probably controlled by archaeal

soil acidification due to chemolithotrophs

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

to avoid production of hydrogen sulfide (H2S) due to anoxia

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? View Available Hint(s)

annamox

A process that results in anaerobic ammonia (NH3) oxidation, uses nitrite (NO2-) as the electron acceptor, and produces N2 as the product is the _________ reaction

syntrophy

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

True

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

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

Agricultural application of nitrogen fertilizer

nitrogen fixation

An assimilatory process in which N2 is converted to ammonia (NH3) for incorporation into organic nitrogen-containing molecules is

nitrate leaches out of soils easily due to its negative charge

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 __________.

diffusion from anoxic to oxic region --> oxidation of soluble forms --> metal oxides and hydroxides precipitate --> oxidized metals return to sediments --> bacteria use oxidized metals as electron acceptors

Cycle of use and regeneration of iron and manganese

CO2 in aerobic environments and CO2 plus CH4 in anoxic environments

Decomposition of organic carbon ultimately results in the formation of __________.

anoxic

Environment in which methanogenesis, iron reduction, and sulfide reduction take place

oxic

Environment in which nitrification and sulfide oxidation take place

True

In a global sense, all nutrient cycles are coupled together.

fermentation

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

True

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

the C and N cycles are closely coupled

Industrial production of nitrogenous fertilizers from N2 now equals or exceeds the amount of nitrogen fixation carried out by microbes in the biosphere. The resulting increase in primary production is an example of the fact that __________.

electrons from organic compounds are necessary for this reaction

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

nitrification

The aerobic process that uses ammonium (NH4+) as an energy source is referred to as

True

The disposal of garbage or sewage in the ocean is known to cause the sudden growth of sulfate reducers.

heterotrophs; autotrophs

The general term for organisms that have to use preformed organic molecules is __________ whereas the general term for those that can use CO2 to synthesize organic molecules are ___________

Methanogens are probably present as they produce CH4 and CO2 in anoxic environments.

The introductory passage describes the way that microbes can produce CH4 and CO2 in melting permafrost, especially in saturated, anoxic depressions. Although other types may also be present, what microbes are most likely present to make these products in these conditions?

chemoorganotrophs

The microbes that decompose permafrost carbon to release CH4 and CO2 are most specifically examples of

absorbing 500 billion tons of atmospheric carbon dioxide and over 80% of the trapped heat energy.

The ocean has mitigated the impact of anthropogenic carbon dioxide production by

denitrification

The use of nitrate (NO3-) as an electron acceptor with formation of multiple gaseous end products (N2, N2O, or NO) is