Microbio Quiz 6

Which of the following applies to methylotrophs?

- They use methane and other C1 molecules as electron donors - some use methane as the sole source of carbon and energy - they use methane monooxygenase to split water molecules - they can be used intimately to turn greenhouse gas into vitamins, proteins, or other products useful for human consumptions and industry - they can be used to clean up chlorinated solvents and synthetic chemical spills in the environment

Check all of the following statements that apply to interspecies hydrogen transfer.

- interspecies hydrogen transfer is part of the rumen ecosystem - fermentation with the production of H2 and acetate in the rumen would be thermodynamically unfavorable without methanogens to quickly consume the H2 - interspecies hydrogen transfer involves a fermentative bacterium and a methanogenic archaeon

Based on your analysis of this figure, which of the following best describes the metabolic strategy used by all the anaerobic microbes represented?

Anaerobic respiration

T/F: The nitrogenase enzyme is sensitive to oxygen therefore nitrogen fixation can only be carried out under oxic conditions.

False

nitrogen gas

N2

Place the words describing metabolic strategies and fate of these compounds with the corresponding process within the sulfur cycle.

N2 - Converted to organic form such as amino acids - Nitrogen fixing bacteria and archaea NO3-, SO42-, Fe3+ - Serve as terminal electron acceptors - chemoorganotrophs performing anaerobic respiration NH4+, H2S, Fe3+ - Chemolithoautotrophs, O2 often used as terminal electron acceptor - serve as electron donors

nitrous oxide

N2O

ammonia

NH3

ammonium

NH4+

nitric oxide

NO

nitrite

NO2-

nitrate

NO3-

Match the statements with the reaction that it most accurately describes to test your understanding of nitrogen cycling in microbial ecology.

Nitrification: The oxidation of NH4+ to NO2− and NO3− Nitrogen Fixation: removes N2 from the air with the primary product of NH4+ Denitrification: reduces nitrate through a series of steps to nitrogen gas Ammonification: deamination of organic compounds yielding NH4+

Drag the biogeochemical processes to the proper condition(s) under which they occur in order to compare aerobic and anaerobic biogeochemical processes.

Occurs in aerobic conditions: - carbon monoxide oxidation - nitrification Occurs in both aerobic and anaerobic conditions: - respiration - carbon fixation - methane oxidation - fermentation - sulfur oxidation Occurs in anaerobic conditions: - methanogenesis - denitrification - anammox - nitrogen fixation - sulfate reduction

Drag the biogeochemical processes to the proper group(s) in which they are found in order to review characteristics of microbes important to biogeochemistry.

Only found in prokaryotes: - methanogenesis - methane oxidation - nitrification - denitrification - sulfur oxidation - sulfate reduction - anammox - nitrogen fixation Found in eukaryotes and prokaryotes: - respiration - carbon fixation - fermentation

organic nitrogen

R-NH3

Based on your analysis of this figure, which of the following best explains why sulfate reducing bacteria and methanogens are not typically found in the same sediment ecosystem?

Sulfate reduction has a more negative standard free energy change (ΔG'0) than methanogenesis

These bacteria can oxidize metal compounds exposed during strip mining of coal, dramatically lowering pH and leading to damaging acid run-off into the surrounding ecosystem.

Sulfur-oxidizing bacteria

The global carbon budget involves both sources and sinks. Which statement most accurately explains the current state CO2 flux?

The rate of CO2 entering the atmosphere is occurring much faster than its removal by autotrophic organisms.

The cyanobacteria can be separated from other groups of Gram-negative photosynthetic bacteria because they

are oxygenic phototrophs.