8: Microbial Metabolism Flashcards
Define metabolism, anabolism, and catabolism.
Metabolism: Biochemical processes of breaking down food and producing biomass required to maintain life
Anabolism: Process of making complex molecules out of smaller molecules
Catabolism: Process of breaking down complex molecules into smaller molecules
Compare autotrophs, heterotrophs, chemolithotrophs, and photolithotrophs.
Autotrophs: Organisms that use inorganic compounds as C source and energy sources (plants and algae)
Heterotrophs: Use organic matter as C and energy sources (animals)
Chemolithotrophs: Subset of autotrophs that use a specific chemical other than sunlight as an e- donor and CO2 as a C source
Photolithotrophs: Subset of autotrophs that use sunlight as an energy source
Compare obligate aerobes, facultative anaerobes, and obligate anaerobes. List possible electron acceptors each use. Describe why obligate anaerobes are unable to grow in the presence of oxygen.
Obligate aerobes: Use oxygen as the terminal electron accepter.
Facultative anaerobes: Use oxygen primarily as terminal electron acceptor, but can use other chemicals such as nitrate, iron, or sulfur if oxygen is depleted.
Obligate anaerobes: Use non-oxygen chemicals as TEA such as nitrate, Fe/Me, SO4, or organics
Define methanogenesis. Describe under what conditions it occurs and name the electron donor, electron acceptor, carbon source, and end products.
Methanogenesis occurs when a bacteria uses carbon dioxide as a terminal electron accepter, H2 as a e- donor, organics and CO2 as a C source, and CH4 (methane) is produced as an end product
For fermentation, sulfate reduction, iron reduction, and nitrate reduction, explain under what conditions they occur and name the electron donors, electron acceptors, carbon sources, and end products.
Nitrate Reduction: NO3 TEA, organics e donor and C Source, N2 End Product
Fe/Mn Reduction: Fe3+/Mn4+ TEA, organics e donor and C Source, Fe2+/Mn2+ End Product
Sulfate Reduction: SO42- TEA, organics e donor and C Source, H2S End Product
Fermentation: organics TEA, organics e donor and C Source, H2 End Product
For iron oxidation, hydrogen sulfide oxidation, and hydrogen oxidation, explain under what conditions they occur and name the electron donors, electron acceptors, carbon sources, and end products.
Iron Oxidation: O2 TEA, Fe2+ organics e donor, CO2 C Source, Fe3+ End Product
Hydrogen Sulfide Oxidation: O2 TEA, H2S e donor, CO2 C Source, Fe3+ End Product
Hydrogen oxidation: O2 TEA, H2 e donor, CO2 C Source, Fe3+ End Product
Define Ehand explain its reliability.
Eh is a measure of the tendency of a redox couple to accept an electron. It indicates an energy potential. Measuring Eh is done with a probe, but measurements are not reliable due to an environment not being in equilibrium and the probe not reacting with all redox couples
Describe typical redox zonation observed in contaminated groundwater, taking note of the sequence. Explain which zones yield the most energy and provide bacteria with the fastest growth rates.
Typical redox zonation: 1) BOD respiration, 2) nitrate reduction, 3) Fe reduction, 4) sulfate reduction, 5) fermentation/methanogenesis, 6) DNAPL source.
Oxidation Reduction Potential (ORP) is the measure of a molecule’s ability to exchange electrons with another molecule. The typical redox zonation ORP is ranked as listed above.
Explain why in a contaminated aquifer oxygen reduction doesn’t occur in the Fe3+reduction zone and why methanogenesis doesn’t occur in the Fe3+reducing zone.
Oxygen reduction doesn’t occur in a Fe reduction zone, because the oxygen has already been depleted. Therefore, Fe digesting bacteria dominate over oxygen reducting bacteria in this environment.
Methanogenesis doesn’t occur in a Fe reduction zone because the energy potential for Fe reduction is higher than a methanogenesis zone. Therefore. Fe digesting bacteria dominate over methanogenesis bacteria in this environment.
Definebiotransformation, biodegradation, mineralization, detoxification, cometabolism, and bioremediation.
Biotransformation: Biological conversion of one chemical into another
Biodegradation: Biological conversion of organic compounds to compounds of lower energy
Mineralization: Complete biodegradation of an organic compounds to inorganics
Detoxification: Rendering a contaminant no longer toxic
Cometabolism: Process of biotransformation where the primary substrate, not the polluting chemical, provides energy to bacteria.
Bioremediation: cleanup of pollution using living organisms
