Concept explainers
Bacteria play major roles in both the oxidative and reductive sides of the sulfur cycle. Sulfur- and sulfide-oxidizing bacteria produce
Q If sulfur chemolithotrophs had never evolved, would there be a problem in the microbial cycling of sulfur compounds? What impact would coastal marine eutrophication have on microbial sulfur transformations?
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Brock Biology of Microorganisms (15th Edition)
- Which organisms below take part in the carbon and sulfur cycle? Explain their function in the carbon and sulfur cycle Cellulose degraders Sulfate reducers Sulfur oxidizers Photosynthetic oxygenic organisms Photosynthetic non-oxygenic organismsarrow_forward. The anaerobic, chemoautotrophic archaeobacterium Methanococcus jannaschii uses which of the following carbon-fixation pathways to obtain organic carbon from CO2? the Hill reaction the Wood-Ljungdahl pathway the Calvin cycle oxygenic photosynthesis the Krebs cyclearrow_forwardCompare photolithoautotrophy with chemolithoautotrophy. Do you think it is possible for an ecosystem to exist solely on the organic carbon generated by chemolithotrophy (i.e., without any contribution by photosynthetic organisms)? Explain your reasoning.arrow_forward
- The carbon cycle is one of the nature's processes that exhibits energy flow, via the transfer of chemical energy in carbohydrates, through ecosystems. True False For many organisms, including humans, the terminal electron acceptor is oxygen, the reduced form of this terminal electron acceptor is water, and the overall process is called anaerobic cellular respiration. True Falsearrow_forwardPhotosynthetic organisms are normally considered the most important primary producers; which organisms are primary producers in hydrothermal vent communities?arrow_forwardThe anaerobic, chemoautotrophic archaeobacterium Methanococcus jannaschii uses which of the following carbon-fixation pathways to obtain organic carbon from CO2? the Hill reaction the reductive acetyl-CoA pathway the Calvin cycle oxygenic photosynthesis the Krebs cyclearrow_forward
- Regarding nitrogen fixation, are the following statements True or False? a) Atmospheric nitrogen is reduced to the biologically useful form NH3 (or NH4 ). b) Nitrogen fixation in nature and in the lab requires a metal cofactor or catalyst. c) The availability of fixed nitrogen limits biological productivity. d) Ammonium from the atmosphere is fixed to more usable forms of nitrogen, such as nitrite (NO2–). e) Nitrogen fixation is energetically neutral, using a negligible amount of ATP. f) The enzyme nitrogenase, which takes part in nitrogen fixation, is inactivated by oxygen.arrow_forwardFigure 22.19 Which of the following statements about the nitrogen cycle is false? Nitrogen fixing bacteria exist on the root nodules of legumes and in the soil. Denitrifying bacteria convert nitrates (NO3 ) into nitrogen gas (N2). Ammonification is the process by which ammonium ion (NH4+) is released from decomposing organic compounds. Nitrification is the process by which nitrites (NO2-) are converted to ammonium ion (NH4+).arrow_forwardWhich one of the following reactions is an example of nitrogen fixation? A)N2O5(g) NO3(g) + NO2(g) B)N2(g) + O2(g) 2NO(g) C)3NO2(g) + H2O(l) 2HNO3(aq) + NO(g) D)2NO(g) + O2(g) 2NO2(g) E)2NH3(g) 3H2(aq) + N2(g)arrow_forward
- “The mechanistic complexity of nitrogenase is necessary because nitrogen fixation is a thermodynamically unfavorable process.” True or false? Explainarrow_forwardWhich of the following pathways is used to fix inorganic carbon into organic form (like methane), by the anaerobic, chemoautotrophic archaeobacterium Methanococcus jannaschii? the reductive acetyl-CoA pathway the Hill reaction the Krebs cycle the Calvin cycle oxygenic photosynthesisarrow_forwardAll of the following carbon sources can be used for nutrition, by at least some exclusively heterotrophic organisms, with the exception of: CH3CH2OH CO2 HCOOH CH4 CH3COOHarrow_forward
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