L14 - Chemolithotrophy Flashcards
What is chemolithotrophy?
the use of inorganic compounds as electron donors in metabolism
What are chemolithotrophs? What are pure chemolithotrophs and what are mixotrophs?
organisms that obtain energy from the oxidation of inorganic compounds. pure = energy purely from inorganic. mixotroph = chemolithotrophs that require organic carbon as a carbon source
How does different oxidation reactions exist in the environment
many sources of reduced molecules exist in the environment the oxidation of different reduce compounds yields varying amount of energy
How does hydrogen (H2) oxidation work? what carries it out? what catalyses it?
And aerobic hydrogen oxidizing bacteria and IKEA are known to carry out hydrogen oxidation. It is catalyzed by hydrogenized enzyme and coupling it with carbon cycle allows, chemo, trophic growth.
What is the role of hydrogenase in cellular metabolism?
Hydrogenase interacts with gaseous hydrogen (H₂), oxidizing it and passing electrons through cytochromes to generate energy.
How are electrons from hydrogen oxidation used in cellular processes?
Electrons from hydrogen oxidation are passed through cytochromes, using NAD to reduce CO₂ and generate a proton motive force.
How is energy generated during hydrogen oxidation?
The energy from hydrogen oxidation generates a proton motive force, which is used to synthesize ATP.
Describe the oxidation of reduced sulphur compounds. Why is sulphur good for this?
there is a large variety of reduced sulfur compounds that can be used as electron donors since they have lot of oxidation states.
What is the main product of this oxidation and what happens to its surroundings
One product of sulfur oxidation is proton H+, which lowers the pH of its surroundings.
What is sox system?
oxidizes reduced sulphur compounds directly to sulphate
Oxidation of reduced sulphur compounds is usually _____ (aerobic or anaerobic) but some organisms can use __ as e- acceptor
- aerobic
- nitrate
What are the oxidation states of sulphur
-2,-1,0,-2,+6,+4,+6
WHat is oxidized to what in Iron (Fe2+) oxidation?
ferrous iron (Fe2+) is oxidized to ferric iron (Fe3+)
WHat is ferric hydroxide?
rust, precipitates in water and forms rust
What is the pH at which many Fe oxidizers can grow? What is it associated with?
<1, acidic pollution from coal mining activities
some _____ ____ can oxidize Fe2+ ____ using Fe2+ as an electron donor for CO2 reduction
anoxygenic phototrophs
anaerobically
Fe3+ formed reacts with water to form _____ (what color is it)
rust (ferric hydroxide), orange
How is Iron oxidation carried out in bacteria?
- Fe2+ oxidation begins extracellularly
- c-type cytochrome oxidizes Fe2+ to Fe3+
- 3- passed to rusticyanin in periplasm
- rusticyanin reduces cytochrome c and reduces cytochrome a
- cytochrome a interacts with O2 to form H2O
- ATP synthesized
- autotrophy in acidithiobacillus ferrooxidans is driven by the calvin cycle
Examples of compounds that serve as electron donors in sulphate reduction
H2, organic compounds, phosphite
How do sulphur-reducing bacteria gain additional energy?
through disproportionation of sulphur compounds
Where is sulphur stored on earth? as what compounds?
the bulk of sulphur on earth occurs in sediments and rocks as sulphate and sulphide minerals (e.g. gypsum, pyrite). the ocean represent the most significant reservoir of sulphur (as sulphate) in the biosphere
What are the key processes in the sulphur cycle
sulphide/sulphur oxidation, sulphate reduction, sulphur reduction, sulphur disproportionation, organic sulphur compound oxidation or reduction, desulphurylation
What is the role of sulphur in proteins, and how is it assimilated?
Sulphur is an important element in proteins, and it is assimilated into proteins from sulphate through assimilation reactions, where sulphate is reduced to incorporate sulphur into organic compounds.
What are desulfurization and disproportionation reactions in sulphur metabolism?
Desulphurization reactions result in sulphur being lost back to organic sources, while disproportionation involves the oxidation of elemental sulphur to sulphate and reduction to sulphide.
How do bacteria manage oxidation and reduction of sulphur, and what is the significance of their cell structure?
Bacteria carry out both oxidation and reduction reactions simultaneously at the interface between oxic and anoxic environments. They elongate their cells, which facilitates electron transport for sulphur metabolism, including the reduction of pure sulphur to H₂S.
What is hydrogen sulphide and how is it produced? how is it removed?
hydrogen sulphide is a major volatile so for gas that is produced by bacteria via sulphate reduction or emitted from Geochemical sources. It is toxic to many plants and animals and reacts with numerous metals, sulphur chemolithotrophs can oxidise sulphide and elemental sulphur at oxic/anoxic interfaces.
How is hydrogen sulphide useful?
eact with metal compounds to remove metal contamniation (metal sulfides formed under redutive reactions → insoluble so its not leaked into oceans
Organic sulphur compounds can also be metabolized by ____
microorganisms
What is the most abundant organic sulphur compound in nature? where is it produced?
dimethyl sulphide (DMS), marine environments as a degradation product of dimethylsulphoniopropionate (algal osmolyte)
Why is iron one of the most abundant elements on earth’s crust
produced by fusion in stars, iron is accumulated
What else is present on earth’s surface, how many oxidation states does it exist in?
manganese can also be oxidized or reduced, exists in 2 oxidation states
How is Fe2+ and Fe3+ turned into Fe0
smelting of ores
How are oxidation and reduction reactions in the environment separated spatially?
Oxidation and reduction reactions are separated in the environment depending on the availability of oxygen, with oxic conditions at the top and anoxic conditions below.
What happens under oxic conditions in the environment?
A: In oxic conditions, iron and manganese are oxidized, forming insoluble compounds that sink through the water column.
What occurs in lower, anoxic conditions in the environment?
n anoxic conditions, reduced compounds lead to the consumption of acetate, which remains soluble and mixes with the water column, rising to the surface.
Describe the phosphorous cycle. why is it limiting and how do we use it?
In the bio of fear, there exists organic and inorganic phosphates which cycles through living organisms, modern soil phosphorus is in a DNA backbone. It is very important however it is limiting in terms of its availability, so humans tend to add additional phosphorus and fertilizers to boost agricultural productivity.
Describe the calcium cycle
reservoirs are rocks and oceans marina phototrophic microorganisms uses Ca2+ to form exoskeleton
