micro algae 2

What is the main structural difference between eukaryotic and prokaryotic cells?

Eukaryotic cells have membrane-bound organelles, including a nucleus; prokaryotic cells do not.

What is the typical structure of a bacterial genome?

One circular DNA chromosome, often several million base pairs long.

What distinguishes a draft genome from a complete genome?

A draft genome contains contigs or scaffolds and may have gaps; a complete genome has no sequence gaps.

What does ORF stand for?

Open reading frame, a stretch of DNA that may encode a protein.

How are genome size and number of ORFs generally related in bacteria?

Larger bacterial genomes generally contain more ORFs.

Can bacteria have linear chromosomes or multiple chromosomes?

Yes. Although a single circular chromosome is typical, exceptions include linear and multiple chromosomes.

What are pathogenicity islands?

Genome regions containing genes associated with virulence and disease-causing ability.

What is notable about Buchnera in aphids?

Buchnera is an obligate mutualistic endosymbiont associated with genome reduction.

What is notable about Candidatus Carsonella ruddii?

It is an obligate psyllid endosymbiont with an extremely small genome of about 160 kbp.

What does a food chain illustrate?

How energy and food pass among producers and consumers.

What is decomposition?

Physical and chemical breakdown of dead plant and animal biomass.

How do decomposers obtain nutrients?

They absorb breakdown products at the molecular scale; bacteria and fungi are examples.

What is detritus?

Dead organic material that supports detritivores and decomposers.

What is a biogeochemical cycle?

Movement of a chemical substance through living and nonliving Earth compartments.

Which Earth compartments are biotic and abiotic?

The biosphere is biotic; the atmosphere, hydrosphere, and lithosphere are abiotic.

Why is phosphorus essential to cells?

It is required for ATP, DNA, RNA, and cell membranes.

Does the phosphorus cycle have a major gaseous phase?

No, the phosphorus cycle lacks a major atmospheric gaseous phase.

How does decomposition affect atmospheric carbon?

It returns carbon to the atmosphere, including as carbon dioxide.

What is carbon fixation?

Conversion of inorganic carbon, such as CO2, into organic matter.

What is oxygenic photosynthesis?

Photosynthesis using water as an electron donor and releasing oxygen.

Write the overall oxygenic photosynthesis equation.

6 CO2 + 6 H2O + light → C6H12O6 + 6 O2.

What is anoxygenic photosynthesis?

Light-driven photosynthesis that does not produce oxygen; some bacteria use reduced sulfur compounds.

Which bacteria perform anoxygenic photosynthesis?

Examples include purple and green sulfur or nonsulfur bacteria.

What is a Winogradsky column?

A layered mud-and-water culture that develops microbial zones under different chemical and light conditions.

What is a meromictic lake?

A lake whose deep and surface waters do not completely mix.

Which domain contains methanogens?

Archaea.

What is methanogenesis?

Microbial production of methane under anaerobic conditions.

What is methylotrophy?

Growth using reduced one-carbon compounds as carbon and/or energy sources.

Why is sulfur biologically important?

Sulfur is a component of proteins and other essential cellular compounds.

What are three key sulfur oxidation states discussed in class?

−2 in sulfide, 0 in elemental sulfur, and +6 in sulfate.

What is sulfate reduction?

Anaerobic microbial reduction of sulfate to reduced sulfur, often sulfide.

What is sulfur oxidation?

Microbial conversion of reduced sulfur compounds into more oxidized sulfur forms.

What is Beggiatoa?

A filamentous sulfur bacterium common near boundaries between oxic and anoxic environments.

What is Thiomargarita namibiensis?

A large sulfur bacterium found in marine sediments off Namibia.

How does SO2 contribute to acid rain?

Atmospheric sulfur dioxide can form sulfuric acid that returns in precipitation.

Why is nitrogen essential for life?

It is a component of amino acids and nucleic acids.

What are the two steps of nitrification?

Ammonia oxidation to nitrite, followed by nitrite oxidation to nitrate.

What does ANAMMOX mean?

Anaerobic ammonium oxidation, a microbial process that converts ammonium and nitrite to nitrogen gas.

Which ammonia oxidizers are especially abundant in open oceans?

Ammonia-oxidizing archaea (AOA), compared with ammonia-oxidizing bacteria (AOB).

What are phytoplankton?

Small, drifting photosynthetic organisms that act as primary producers in marine food webs.

What factors influence phytoplankton blooms?

Nutrients, light, temperature, salinity, currents, grazing, and ecological interactions.

What are diatom frustules made of?

Silica.

What are coccolithophores covered with?

Calcium carbonate plates called coccoliths.

What distinguishes dinoflagellate movement?

They have two different flagella, one associated with spinning and one with forward motion.

Which cyanobacteria are prominent in nutrient-poor subtropical gyres?

Prochlorococcus and Synechococcus.

What are the epipelagic and mesopelagic zones?

The sunlit surface zone (roughly 0–200 m) and twilight zone (roughly 200–1,000 m).

What is the ecological significance of marine viruses?

They are extremely abundant and influence microbial mortality and nutrient cycling.

Why is nitrification important in aquaculture?

It helps remove ammonia and nitrite, which can be toxic to aquatic organisms.

Are all archaea extremophiles?

No. Many archaea live in ordinary marine environments.

What is dissolved organic carbon (DOC)?

Organic carbon in material small enough to pass through the filter used to separate dissolved from particulate matter.

Where is much marine DOC produced?

In the euphotic zone, including through phytoplankton activity.

What is the microbial loop?

Transfer of dissolved organic matter through heterotrophic bacteria and microbial consumers into the food web.

What is an oxygen minimum zone (OMZ)?

An ocean layer with much lower dissolved oxygen than waters above and below.

Which nitrogen processes occur near oxygen minimum zones?

Processes include nitrification near upper boundaries and anaerobic nitrogen transformations in low-oxygen waters.

What is the average depth of the global ocean given in the lecture?

Approximately 3,700 meters.

What is a psychrophile?

An organism adapted to grow in cold conditions.

What is a piezophile?

An organism adapted to high hydrostatic pressure.

What is bioluminescence?

Production and emission of light by living organisms.

What are milky seas?

Large areas of ocean that glow continuously at night, associated with microbial bioluminescence.

What are marine sediments composed of?

Mineral particles, organic matter, biological remains, and associated porewater.

What is porewater?

Water occupying spaces between sediment grains and carrying dissolved substances.

Name four sources of marine sediment.

Lithogenous, biogenous, hydrogenous, and cosmogenous.

How does oxygen availability change with sediment depth?

It generally decreases, creating different microbial metabolic zones.

What metabolism is characteristic of oxic surface sediments?

Aerobic respiration and nitrification.

What processes are associated with suboxic sediment?

Denitrification and manganese or iron reduction.

Why is sulfate reduction prominent in marine sediments?

Seawater contains abundant sulfate, approximately 28 mM.

What processes are associated with deeper methanogenic sediment?

Methane production and fermentation.

What is a metagenome-assembled genome (MAG)?

A genome reconstructed from metagenomic sequence data by assembly and binning.

What role do seagrass sediments play in biogeochemical cycling?

They trap organic particles and support microbial carbon, sulfur, and nutrient transformations.

What is a lotic freshwater system?

Flowing water, such as rivers, streams, and creeks.

What is a lentic freshwater system?

Standing water, such as lakes, ponds, and reservoirs.

What are typical freshwater wetland habitats?

Marshes, swamps, bogs, and fens.

What is the hyporheic zone?

The mixing region between stream water and groundwater beneath and alongside a streambed.

What is a biofilm?

A community of microorganisms attached to a surface.

What is bacterioplankton?

Bacteria suspended in the water column.

What does oligotrophic mean?

Low in nutrients and typically low in biological productivity.

What does eutrophic mean?

Nutrient-rich and often highly productive, with potential for algal blooms.

Why can freshwater sediments favor methanogenesis at shallower depths than marine sediments?

Freshwater sediments often contain less sulfate, reducing competition from sulfate reducers.

What challenges do temporary freshwater habitats pose for microbes?

Drying and rewetting require dormancy, dispersal, or rapid regrowth.