WorksheetsMicrobial Iron Cycle Quiz
Total questions: 30
Worksheet time: 15mins
Which oxidation state of iron is predominantly used as an electron donor in microbial iron oxidation?
Fe³⁺
Fe²⁺
Fe⁰
Fe⁴⁺
Which group of bacteria is primarily responsible for the oxidation of Fe²⁺ under acidic conditions?
Geobacter
Acidithiobacillus
Shewanella
Nitrosomonas
What is the main product of microbial iron oxidation in neutral pH environments?
Ferrihydrite
Magnetite
Goethite
Pyrite
Which type of bacteria can reduce Fe³⁺ to Fe²⁺ under anaerobic conditions?
Nitrifying bacteria
Sulfate-reducing bacteria
Iron-reducing bacteria
Methanogenic bacteria
In the microbial iron cycle, which process is typically coupled with the oxidation of Fe²⁺?
Nitrate reduction
Sulfate reduction
Methane oxidation
Oxygen reduction
What is the primary electron acceptor used by iron-reducing bacteria in anoxic environments?
Sulfate (SO₄²⁻)
Ferric iron (Fe³⁺)
Oxygen (O₂)
Nitrate (NO₃⁻)
Which of the following is a key intermediate in dissimilatory iron reduction?
Ferrihydrite
Magnetite
Goethite
Siderite
What is the ecological significance of microbial iron reduction in sediments?
Produces methane as a byproduct
Detoxifies heavy metals
Facilitates the cycling of organic carbon
Converts ferric iron into hematite
Which metabolic pathway is used by Shewanella species for iron reduction?
Methanogenesis
Dissimilatory metal reduction
Oxidative phosphorylation
Fermentation
What type of environmental conditions favor microbial iron oxidation by phototrophic bacteria?
Acidic and aerobic
Alkaline and anaerobic
Neutral and anoxic with light
Acidic and anoxic
What is a key feature of extracellular electron transfer in iron-reducing bacteria?
Involves the reduction of oxygen
Requires direct contact with iron minerals
Uses photosystem proteins
Involves methane production
Which mineral is commonly associated with the deposition of oxidized iron in marine environments?
Pyrite
Hematite
Ferrihydrite
Magnetite
What is the role of siderophores in the microbial iron cycle?
Oxidize Fe²⁺ to Fe³⁺
Reduce Fe³⁺ to Fe²⁺
Solubilize Fe³⁺ for microbial uptake
Precipitate iron as iron sulfide
Which process in the microbial iron cycle contributes to acid mine drainage?
Iron reduction
Iron oxidation
Ammonification
Methanogenesis
Which of the following microbes is a known phototrophic iron oxidizer?
Chlorobium ferrooxidans
Geobacter sulfurreducens
Acidithiobacillus ferrooxidans
Shewanella oneidensis
What is the energy yield of microbial Fe²⁺ oxidation compared to other electron donors like H₂ or CH₄?
Higher energy yield
Lower energy yield
Equal energy yield
Variable depending on pH
Which bacterial genera is associated with magnetite biomineralization during iron reduction?
Nitrosomonas
Geobacter
Acidithiobacillus
Rhizobium
What is a common consequence of microbial iron oxidation in freshwater systems?
Formation of iron sulfide precipitates
Depletion of dissolved oxygen
Release of methane gas
Increase in sulfate concentration
Which environmental factor most strongly influences microbial iron reduction rates?
Light availability
Temperature
pH
Oxygen concentration
In the context of the microbial iron cycle, what is the significance of 'microbial nanowires'?
Aid in oxygen uptake for iron reduction
Facilitate extracellular electron transfer to Fe³⁺
Enhance the solubilization of Fe³⁺
Catalyze the precipitation of iron minerals
Which process in the microbial iron cycle involves the oxidation of ferrous iron (Fe²⁺) to ferric iron (Fe³⁺)?
Iron reduction
Iron oxidation
Dissimilatory iron reduction
Anammox
Which microorganism is a well-known iron-reducing bacterium?
Geobacter sulfurreducens
Acidithiobacillus ferrooxidans
Nitrosomonas europaea
Rhizobium leguminosarum
What is the primary electron acceptor in microbial iron reduction?
Oxygen
Nitrate
Ferric iron (Fe³⁺)
Ammonium
In which type of environment is microbial iron oxidation most commonly observed?
Oxygen-rich, acidic conditions
Anoxic, alkaline conditions
High-salinity, low-temperature conditions
Methane-rich environments
What is the primary ecological role of microbial iron oxidation in natural systems?
Removal of heavy metals
Cycling of sulfur
Formation of iron oxides
Fixation of atmospheric nitrogen
Which form of iron is most soluble in water and readily available to microbes?
Ferric iron (Fe³⁺)
Ferrous iron (Fe²⁺)
Metallic iron (Fe⁰)
Iron sulfide (FeS)
Which of the following is a common product of microbial iron reduction?
Hematite (Fe₂O₃)
Goethite (FeOOH)
Magnetite (Fe₃O₄)
Pyrite (FeS₂)
What is the role of siderophores in the microbial iron cycle?
Oxidation of Fe²⁺ to Fe³⁺
Solubilization and chelation of Fe³⁺
Reduction of Fe³⁺ to Fe²⁺
Precipitation of iron as iron sulfide
Which type of bacteria oxidize Fe²⁺ under anaerobic conditions using nitrate as an electron acceptor?
Phototrophic bacteria
Lithotrophic iron-oxidizing bacteria
Denitrifying iron-oxidizing bacteria
Methanogenic bacteria
What is a significant consequence of microbial iron oxidation in mining environments?
Increased methane production
Generation of acid mine drainage
Depletion of nitrate levels
Reduction in sulfate concentration
