MMG 301 - Module 29: Biogeochemical Cycles and Bioremediation

What is the major reservoir of stable nitrogen?

N2

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

True

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

True

Syntrophic organisms cannot grow fermentatively without a hydrogen-consuming partner organism. T/F

True

Why is U4+ a preferred form of uranium over U6+?

U4+ is insoluble, so it will not contaminate groundwater.

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.

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

CO2 in aerobic environments and CO2 plus CH4 in anoxic environments

________ is a term used to describe dead organic matter.

Humus

Which of the following processes does denitrification contribute to?

acid rain, ozone depletion, and global warming

Nitrogen fixation results in the

addition of biologically available N to an ecosystem.

While most of the oil spilled into the Gulf of Mexico from the Deepwater Horizon drilling rig in 2010 has disappeared, some of the oil spilled from the Exxon Valdez oil tanker into Prince William Sound, Alaska, in 1989 still remains in the coastal sand and sediments. What possible differences in these two spills could account for the different rates of petroleum degradation?

ambient temperatures and the types of hydrocarbons present

Denitrification contributes to global warming by __________.

destroying ozone

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

fermentation

The two major forms of carbon that remain following microbial degradation are

methane and carbon dioxide.

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 __________.

nitrate leaches out of soils easily due to its negative charge

Which organisms form the foundation of the carbon cycle?

phototrophs

Nitrous oxide (N2O) is a

potent greenhouse gas that is a product of denitrification.

The metabolic process of denitrification

reduces NO3-.

As a microbiologist, you have been asked to advise a town council on the possible ways to remove PCB contaminants from the local groundwater. Which microbial process is most likely to have bioremediation potential in this case?

reductive dechlorination

Ecologically, which transformation is most important in degrading chlorinated xenobiotics?

reductive dechlorination

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

syntrophy

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 __________.

the C and N cycles are closely coupled

Compounds that are NOT produced by organisms anywhere in nature are called __________.

xenobiotic