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What is the significance of Cyanobacteria in ecosystems?
Which of the following bacteria is NOT a pathogenic species?
What is unique about the habitat of Extreme Halophiles?
What is the primary function of Chemoheterotrophic prokaryotes in ecosystems?
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Which of the following is an example of a symbiotic relationship?
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What is the characteristic of Proteobacteria that allows them to thrive in a variety of environments?
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What is the byproduct of Methanogens' metabolic activities?
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Which of the following extremophiles thrive in very hot environments?
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What is the primary function of fimbriae in prokaryotes?
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What is the term for the movement of bacteria towards or away from a chemical stimulus?
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What is the composition of bacterial flagella?
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What is the region of the prokaryotic cell where the genome is located?
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What is the term for the process by which bacteria reproduce?
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What is the primary factor contributing to genetic diversity in bacteria?
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What is the process called when a prokaryotic cell takes up and incorporates foreign DNA from the surrounding environment?
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What is the term for the metabolically inactive structures formed by some bacteria to survive harsh conditions?
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Which of the following is an example of a symbiotic relationship involving prokaryotes?
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What is the purpose of pili (or sex pili) in prokaryotes?
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Which of the following is a characteristic of obligate anaerobes?
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Which of the following prokaryotes is an example of an extremophile?
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What is the term for the process by which some prokaryotes convert atmospheric nitrogen to ammonia?
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Which of the following is a characteristic of facultative anaerobes?
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Which of the following prokaryotes is an example of a pathogenic bacterium?
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Which of the following is NOT a mode of nutrition in prokaryotes?
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What is the surprising feature of the phylogenetic tree regarding Eukarya and Archaea?
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Which group of Archaea is found in a broad range of environments?
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Which domain of life includes organisms that are widely diverse and found in many environments?
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Which type of Proteobacteria is associated with stomach ulcers?
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What is a common feature of extremophiles?
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What is a characteristic of Gram-positive bacteria?
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What is a characteristic of Chlamydia?
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Which group of Bacteria includes Rhizobium, which forms nodules in plant roots?
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Study Notes
Genetic Recombination
- A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment in a process called transformation.
- Transduction is the movement of genes between bacteria by bacteriophages (viruses that infect bacteria).
- Conjugation is the process where genetic material is transferred between prokaryotic cells.
- In bacteria, the DNA transfer is one way, from a donor cell to a recipient cell.
- A donor cell attaches to a recipient by a pilus, pulls it closer, and transfers DNA.
- A piece of DNA called the F factor is required for the production of pili.
Metabolism and Nutrition
- Prokaryotes can be categorized by how they obtain energy and carbon.
- Phototrophs obtain energy from light.
- Chemotrophs obtain energy from chemicals.
- Autotrophs require CO2 as a carbon source.
- Heterotrophs require an organic nutrient to make organic compounds.
- Nitrogen is essential for the production of amino acids and nucleic acids.
- In nitrogen fixation, some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3).
- In the cyanobacterium Anabaena, photosynthetic cells and nitrogen-fixing cells called heterocysts exchange metabolic products.
Prokaryotic Metabolism
- Prokaryotic metabolism varies with respect to O2.
- Obligate aerobes require O2 for cellular respiration.
- Obligate anaerobes are poisoned by O2 and use fermentation or anaerobic respiration.
- Facultative anaerobes can survive with or without O2.
Prokaryotic Diversity
- Domain Archaea shares certain traits with bacteria and other traits with eukaryotes.
- Some archaea live in extreme environments and are called extremophiles.
- Extreme halophiles (Clade Euryarchaeota) live in highly saline environments.
- Extreme thermophiles (Clade Crenarchaeota) thrive in very hot environments.
- Methanogens (Clade Euryarchaeota) live in swamps and marshes and produce methane as a waste product.
- Methanogens are strict anaerobes and are poisoned by O2.
Domain Bacteria
- Proteobacteria are gram-negative bacteria that include photoautotrophs, chemoautotrophs, and heterotrophs.
- Some are anaerobic, and others aerobic.
- Chlamydia are parasites that live only within animal cells.
- Cyanobacteria are photoautotrophs that generate O2.
- Gram-positive bacteria include Actinomycetes, which decompose organic matter, and Bacillus anthracis, the cause of anthrax.
Ecological Importance
- Prokaryotes play a major role in the recycling of chemical elements between the living and nonliving components of ecosystems.
- Chemoheterotrophic prokaryotes function as decomposers, breaking down dead organisms and waste products.
- Prokaryotes can increase the availability of nitrogen, phosphorus, and potassium for plant growth.
- Symbiosis is an ecological relationship in which two species live in close contact: a larger host and smaller symbiont.
- Some prokaryotes have fimbriae, which allow them to stick to their substrate or other individuals in a colony.
Locomotion
- Many bacteria exhibit taxis, the ability to move toward or away from a stimulus.
- Chemotaxis is the movement toward or away from a chemical stimulus.
- Most motile bacteria propel themselves by flagella scattered about the surface or concentrated at one or both ends.
- Bacterial flagella are composed of a motor, hook, and filament.
Internal Organization
- Prokaryotic cells usually lack complex compartmentalization.
- Some prokaryotes do have in-foldings of the plasma membrane that perform metabolic functions.
- Most of the genome consists of a circular chromosome located in the nucleoid region.
- Some species of bacteria also have smaller rings of DNA called plasmids.
Prokaryotic Reproduction
- Bacteria are small, reproduce by binary fission (1-3 hours), and have short generation times.
- Many prokaryotes form metabolically inactive endospores, which can remain viable in harsh conditions for centuries.
- Rapid reproduction, mutation, and genetic recombination contribute to genetic diversity in bacteria.
- Mutation rates during binary fission are low, but rapid reproduction allows for rapid evolution.
Domain Diversity
- The three main domains of life are Eukarya, Archaea, and Bacteria
- Eukarya and Archaea are sister taxa, despite being eukaryotic and prokaryotic respectively
Archaea
- Archaea are extremophiles, living in extreme environments
- Examples of extreme environments include salt-loving (halophiles) and heat-loving (thermophiles)
- There are five groups of Archaea:
- URI Archaea, found in a broad range of environments
- Thermophiles, found in hot springs
- Methanogens, generating methane as a byproduct of metabolism
- Others
Domain Bacteria
- Bacteria are a widely diverse group of organisms found in many environments
- While some bacteria perform beneficial functions, others are responsible for diseases
- Subdivisions of bacteria include:
- Proteobacteria, which are gram-negative
- Chlamydia, which are gram-negative and mostly parasitic
- Spirochetes, which are gram-negative and have a helical shape
- Cyanobacteria, which are gram-positive and photosynthetic
- Gram-positive bacteria, including Bacillus, Clostridium, and Staphylococcus
Proteobacteria
- Examples of Proteobacteria include:
- Alpha Proteobacteria, such as Rhizobium, which forms nodules in plant roots
- Gamma Proteobacteria, such as Pseudomonas fluorescens, which is a nitrogen-fixing bacteria
- Delta Proteobacteria, such as Myxobacteria, which attack other bacteria and take their resources
- Epsilon Proteobacteria, such as Helicobacter pylori, which is associated with stomach ulcers
Chlamydia
- Examples of Chlamydia include:
- Chlamydia trachomatis, which is responsible for non-gonococcal urethritis (a sexually transmitted disease)
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Description
This quiz covers the different ways genetic material is transferred between prokaryotic cells, including transformation, transduction, conjugation, and horizontal gene transfer.
