Unit 3 Review
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Microorganisms in the sulfur cycle can perform 2 types of metabolism. Give and define them
• Assimilative= oxidation of sulfur compounds; create organic sulfur compounds for organism • Dissimilative= reduction of sulfur compounds; getting energy from sulfur compounds (respiration)
The 5 groups of bacteria and Archaea that control the sulfur cycle are:
• Purple sulfur bacteria • green sulfur bacteria • sulfate reducers • sulfur reducers • sulfur oxidizers
Green sulfur bacteria and purple sulfur bacteria are ______ phototrophs, meaning
anoxygenic they can perform photosynthesis without oxygen
Sulfate Reducers Energy sources (2): Produce:
Sulfate Reducers Use H2 & organic compounds (lactate) as energy sources Produce H2S via sulfate respiration
Which bacteria (2) and archaea (1) are sulfate reducers?
Bacteria: proteobacteria (1 group) and firmicutes Archaea: Euryarchaeota
Sulfate reducers are ____ anaerobes, meaning they perform sulfate respiration in the absence of oxygen
obligatory
Give 2 alternative metabolisms that sulfate reducers can use
• nitrite reduction • fermentation (products= H2, CO2, acetate)
List the 7 famous sulfate reducers (6 bacteria, 1 archaea)
Bacteria: - Desulfomonas - Desulfotomaculum - Desulfobacter - Desulfovibrio - Thermodesulfobacterium - Thermodesulfovibrio Archaea: - Archaeoglobus
Sulfur reducers use what as an energy source? (2) these act as the electron ___
• H2 • Organic compounds these act as the electron donor
Which bacteria (1) and archaea (1) are sulfur reducers?
3 groups of proteobacteria and crenarchaeota (archaea)
Sulfur reducers are typically _____ anaerobes, but can use ____aerobic strategies as an alternative metabolism
anaerobes facultative
Sulfur oxidizers use ___ and ___ as their energy source (ie electron donor)
H2S S
Which bacteria and archaea are sulfur oxidizers?
3 subgroups of proteobacteria crenarchaeota
Is Acidithiobacillus ferrooxidans a sulfur oxidizer or a sulfur reducer?
oxidizer
Acidithiobacillus ferrooxidans uses ___ as its electron donor
FeS2
How can Acidithiobacillus ferrooxidans be beneficial for mining?
• it oxidizes FES2, releasing iron from sulfur • This is bioleaching= metal extraction from ores via microorganisms • helps humans with the mining process
How can Acidithiobacillus ferrooxidans be harmful for mining?
Bioleaching (caused by oxidation of FeS2) can cause unwanted acidification and can release toxic metals (eg cadmium, aluminum)
It’s possible for many oxidizers to use H2S and O2 together because of the evolution of ecological strategies. List these 3 potential strategies. Why are these strategies needed?
• O2 dependent positioning • Anaerobic vacuole • Symbiotic association Needed because H2S and O2 are VERY reactive together
Describe the hypothesis of O2 dependent positioning to explain how sulfur oxidizers can use both H2S and O2
• cyanobacteria produce O2 via photosynthesis in the daytime (on top of microbial mats) • Beggiatoa (a bacteria) stays on the bottom of the mats during the day, and comes up for O2 at night Both H2S= oxidized and O2= reduced –> produces energy
Describe the hypothesis of the anaerobic vacuole to explain how sulfur oxidizers can use both H2S and O2
• bacteria “thiomargarita” uses this • Bacteria uses H2S and NO3- (nitrate resp) –> makes S and NH4+ • this process occurs in a vacuole, where the S and NH4+ is stored • Bacteria uses S and O2 for energy generation instead of H2S and O2
Describe the hypothesis of symbiotic association to explain how sulfur oxidizers can use both H2S and O2
• eukaryotic host= yeti crab • this host regulates the levels of H2S and O2 (balances) • bacterium fixes CO2 for the host = symbiosis
_______ is the enzyme that completes nitrogen fixation (it’s O2 sensitive)
nitrogenase
T/F Many diazotrophs evolved the ability to protect nitrogenase from oxygen (cyanobacteria)
true
What are the 3 main groups of organisms that control the nitrogen cycle?
• diazotrophs • nitrifiers • denitrifiers