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Microbial Ecosystems - Pelagic bacteria and archaea

7 important questions on Microbial Ecosystems - Pelagic bacteria and archaea

What is the distribution pattern of prokaryotic cells in pelagic waters concerning depth, and how is this distribution tracked?

The abundance of prokaryotic cells in pelagic waters decreases with depth. In the photic zone, extending to around 200 m, cell numbers are highest, averaging about 10^6 cells/ml in surface waters. Below 1000 m, total cell numbers fall to between 10^3 and 10^5 cells/ml. The distribution is tracked using fluorescence in situ hybridization (FISH) technology.

What is the ecological significance of Pelagic Bacteria and Archaea in marine environments, particularly regarding their role in nutrient cycling and organic matter consumption?

Pelagic Bacteria and Archaea in marine environments play a crucial ecological role by consuming dissolved organic carbon. They contribute to nutrient cycling and are responsible for about half of all marine respiration and nutrient regeneration. These planktonic microbes, despite low nutrient levels, consume about half of the total oceanic organic carbon produced from photosynthesis. This "secondary production" helps return organic matter to the marine food web, benefiting larger organisms, including fish.

Why is Pelagibacter considered the most successful microbial group in terms of abundance, and what are some of its adaptive features?

Pelagibacter is considered the most successful microbial group in terms of abundance, constituting about three-quarters of all Bacteria in the oceans. Its success is attributed, in part, to its small size, with cells being difficult to resolve with a light microscope but having a high surface-to-volume ratio. Pelagibacter is an oligotroph, thriving at very low nutrient concentrations, and its genome is fairly small (1.3 Mbp) with a high number of ABC-type transport systems, enabling efficient nutrient uptake. Additionally, Pelagibacter's streamlined genome reduces replication costs.

Explain the role of rhodopsins, specifically proteorhodopsin, in Pelagibacter, and how does it contribute to the survival of energy-starved cells in the light?

The Pelagibacter genome contains genes encoding proteorhodopsin, a form of the visual pigment rhodopsin. Proteorhodopsin converts light energy into ATP, functioning as a light-driven proton pump. Energy-starved cells containing proteorhodopsin survive starvation better in the light than in the dark. This suggests that light-mediated ATP production compensates for the energy unavailable from carbon respiration when organic carbon levels are low. Proteorhodopsins are widespread in marine bacteria and contribute to supplementing energy metabolism in nutrient-limited conditions.

What are the major bacterial groups recognized as abundant in the ocean, and how do they contribute to marine ecosystems, including their impact on Earth's climate?

Major bacterial groups recognized as abundant in the ocean include Alpha- and Gammaproteobacteria, Cyanobacteria, Bacteroidetes, and to a lesser extent Marinimicrobia and Actinobacteria. Proteobacteria, particularly the alpha and gamma classes, dominate marine microbial diversity. Many marine Alpha- and Gammaproteobacteria metabolize dimethylsulfoniopropionate (DMSP), producing dimethyl sulfide (DMS), which influences Earth's climate. DMS released to the atmosphere contributes to water condensation, cloud formation, and sunlight reflection, ultimately cooling the planet.

What is the composition of Archaea in pelagic waters, and why are ammonia-oxidizing chemolithotrophic Archaea considered important in marine ecosystems?

Archaea in pelagic waters consist mainly of Euryarchaeota, Crenarchaeota, and Thaumarchaeota. Thaumarchaeota, particularly ammonia-oxidizing chemolithotrophic Archaea, are crucial in marine ecosystems. These Archaea play a significant role in coupling the marine carbon and nitrogen cycles by oxidizing ammonia. Nitrosopumilus maritimus, affiliated with Thaumarchaeota, is among the most abundant marine microbes, comprising 20–40% of all marine prokaryotic cells beneath the photic zone.

What are some major bacterial groups present in seawater, and how does the diversity of these groups vary in different marine environments?

Major bacterial groups present in seawater include Alpha- and Gammaproteobacteria, Cyanobacteria, Bacteroidetes, and to a lesser extent Marinimicrobia and Actinobacteria. Proteobacteria, especially the alpha and gamma classes, dominate marine microbial diversity. The diversity of bacterial groups varies in different marine environments; for example, Cyanobacteria, including Prochlorococcus, dominates the nutrient-limited open ocean, while other groups like Alpha- and Gammaproteobacteria are more abundant in higher-nutrient coastal waters.

The question on the page originate from the summary of the following study material:

Brock Biology of Microorganisms, Global Edition | 9781292235103 | Michael T Madigan, et al

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Microbial Ecosystems - Pelagic bacteria and archaea

7 important questions on Microbial Ecosystems - Pelagic bacteria and archaea

What is the distribution pattern of prokaryotic cells in pelagic waters concerning depth, and how is this distribution tracked?

What is the ecological significance of Pelagic Bacteria and Archaea in marine environments, particularly regarding their role in nutrient cycling and organic matter consumption?

Why is Pelagibacter considered the most successful microbial group in terms of abundance, and what are some of its adaptive features?

Explain the role of rhodopsins, specifically proteorhodopsin, in Pelagibacter, and how does it contribute to the survival of energy-starved cells in the light?

What are the major bacterial groups recognized as abundant in the ocean, and how do they contribute to marine ecosystems, including their impact on Earth's climate?

What is the composition of Archaea in pelagic waters, and why are ammonia-oxidizing chemolithotrophic Archaea considered important in marine ecosystems?

What are some major bacterial groups present in seawater, and how does the diversity of these groups vary in different marine environments?

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