Title: Prokaryotes
Course: Question Banks

Q: The earliest forms of life on Earth were ________.
- individual phototrophs (Incorrect. The earliest forms of life were not phototrophs; these appeared about 1 billion years after the formation of Earth.)
- aerobic cyanobacteria (Incorrect. Cyanobacteria appeared about 1 billion years after phototrophs.)
- microbial mats (Correct. The earliest forms of life were most likely microbial mats, a multi-layered sheet of prokaryotes.)
A: microbial mats

Q: Microbial mats obtained their energy from ________.
- solar radiation (Incorrect. On early Earth, solar radiation was not reduced by an ozone layer so it would actually have damaged any biological organisms exposed directly to its rays.)
- eating each other (Incorrect. Producers had to appear in the tree of life before consumers did.)
- hydrothermal vents (Correct. The first microbial mats likely obtained chemical energy from the expulsions from hydrothermal vents on the ocean floor.)
A: hydrothermal vents

Q: The earliest records of life on Earth are ________.
- stalactites (Incorrect. These are crystallized calcium deposits from the roofs of caves.)
- fossilized cells (Incorrect. Early cells would have had no “hard parts” to fossilize.)
- stromatolites (Correct. These structures are formed from minerals precipitated out of water by prokaryotes.)
A: stromatolites

Q: ________ are able to grow and thrive under conditions that would kill most other organisms.
- Prokaryotes (Incorrect. Many prokaryotes require the same living conditions as other organisms like plants and animals.)
- Superbugs (Incorrect. Superbugs is a term applied to bacteria that are resistant to the antibiotics generally used to kill that type of bacteria.)
- Extremophiles (Correct. Extremophiles thrive under conditions that would generally kill other life forms, such as high heat, high salt, or extremes of pH.)
A: Extremophiles

Q: ________ live and thrive in extremely low temperatures.
- Hypothermophiles (Incorrect. There are no “hypothermophiles.”)
- Thermophiles (Incorrect. Thermophiles live at high temperatures, between 60–80oC.)
- Psychrophiles (Correct. Psychrophiles live at temperatures of −15–10 oC.)
A: Psychrophiles

Q: Organisms such as ________ are adapted to survive extreme environments but do not prefer this type of environment.
- extremophilic prokaryotes (Incorrect. Most extremophiles actually prefer, or require, the extreme environments in which they live.)
- osmophiles (Incorrect. Osmophiles require high sugar concentrations for optimal growth.)
- radioresistant prokaryotes (Correct. Some extremophiles, like radioresistant ones, have developed mechanisms to cope with extreme environments but do not prefer these environments.)
A: radioresistant prokaryotes

Q: ________ postulated that an organism that is present in all infected samples but is not present in healthy samples is, in fact, the cause of the infection or disease.
- Petri (Incorrect. Julius Petri developed the petri dish that is still used in most laboratories around the world today.)
- Woese (Incorrect. Carl Woese pioneered the use of small-subunit ribosomal RNA to study the three domains of life.)
- Koch (Correct. Robert Koch was a German physician who developed methods for culturing pure strains of bacteria and using these strains to identify disease causing organisms.)
A: Koch

Q: About ________ percent of bacteria and archaea cannot be cultured.
- 23 (Incorrect. This percentage is not high enough.)
- 82 (Incorrect. This is not the percentage of prokaryote that cannot be cultured.)
- 99 (Correct. Over 99 percent of prokaryotic organisms cannot be cultured in a laboratory setting.)
A: 99

Q: Prokaryotes in a ________ state have experienced stress and respond by “shutting down” but not dying.
- dormant (Incorrect. While these cells are dormant, this is not the term scientists use to describe these prokaryotes.)
- static-but-viable (Incorrect. While this does describe these cells, this is not the term scientists use.)
- viable-but-non-culturable (Correct. VBNC prokaryotes enter a dormant state under environmental stress but do not actually die.)
A: viable-but-non-culturable

Q: Free-living prokaryotes are known as ________.
- biomolecules (Incorrect. Biomolecules are basically the macromolecules that make up biological life.)
- biofilms (Incorrect. Biofilms are actually the opposite of free-living prokaryotes: they are communities of prokaryotes (and occasionally fungi) living together.)
- planktonic (Correct. Planktonic prokaryotes are free-living, individual cells. It is now known that few prokaryotes are actually planktonic.)
A: planktonic

Q: Why do biofilms form?
- Biofilms enable prokaryotes to share resources. (Incorrect. While some sharing of resources occurs, this is not the main reason for biofilm formation.)
- Bacteria require the physical mass to survive. (Incorrect. There is no set or minimum mass to a biofilm.)
- Biofilms create a protective network that makes it harder to kill the bacteria in them. (Correct. The biofilm excludes most antibiotics and disinfectants, protecting the bacterial members.)
A: Biofilms create a protective network that makes it harder to kill the bacteria in them.

Q: ________ are held together by polysaccharide matrix.
- Biological macromolecules (Incorrect. Biological macromolecules are usually held together by covalent bonds.)
- Biomasses (Incorrect. Biomass is held together by a host of chemical interactions.)
- Biofilms (Correct. Biofilms secrete a gummy-textured matrix composed mainly of polysaccharides that holds the film together.)
A: Biofilms

Q: The nucleoid is ________.
- the site of protein synthesis in prokaryotes (Incorrect. Proteins are synthesized throughout the cytoplasm of prokaryotes.)
- a newly formed bacterial cell (Incorrect. The nucleoid is not a cell of any type.)
- an accumulation of prokaryotic DNA (Correct. The nucleoid can be thought of as analogous to the eukaryotic nucleus, though it is not protected in a separate membrane.)
A: an accumulation of prokaryotic DNA

Q: ________ in prokaryotes enables the direct exchange of genetic information between two cells.
- Transduction (Incorrect. While transduction does introduce new genetic material into a prokaryotic cell, it occurs through a viral carrier.)
- Transformation (Incorrect. Transformation involves a cell absorbing DNA found in its environment.)
- Conjugation (Correct. During conjugation, a sex pilus transfers DNA from one cell to another.)
A: Conjugation

Q: In binary fission ________.
- one cell splits in half, halving its DNA as well (Incorrect. This is the process of meiosis in forming gametes.)
- a growth appears on a cell, and the growth is severed off to become a new organism (Incorrect. This sort of, but not quite, describes budding.)
- one cell duplicates its DNA and then pinches in half (Correct. Most prokaryotes reproduce by binary fission in which one cell duplicates its DNA and then pinches in half.)
A: one cell duplicates its DNA and then pinches in half

Q: The cell walls of ________ are composed mainly of peptidoglycan.
- archaea (Incorrect. Archaean cell walls do not contain peptidoglycan; there are actually four different types of cell walls in archaea.)
- fungi (Incorrect. Fungal cell walls contain chitin.)
- bacteria (Correct. Bacterial cell walls are based on peptidoglycan.)
A: bacteria

Q: The ________ in Archaea is different from that of all other domains of life.
- genetic material (Incorrect. Archaea use DNA as their genetic material, as do Bacteria and Eukarya.)
- ribosomes (Incorrect. The basic structure and function of ribosomes is the same in all organisms; that is why they can be used to study the tree of life.)
- cell membrane (Correct. Archaean cell membranes are based on a phospholipid bilayer with phytanyl side chains instead of fatty acids tails. Additionally, the lipid is attached to the glycerol head with an ether bond instead of an ester bond.)
A: cell membrane

Q: ________ are divided into two major groups based on cell wall structure.
- Archaea (Incorrect. There are not two major groups in Archaea.)
- Prokarya (Incorrect. The two major divisions in Prokarya are not based on cell wall structure.)
- Bacteria (Correct. Scientists use Gram staining to distinguish bacteria into either Gram positive or Gram negative groups; the difference in staining results is based on cell wall structure.)
A: Bacteria

Q: The macronutrient ________ is required for the synthesis of nucleotides and phospholipids.
- nitrogen (Incorrect. Nitrogen is required for proteins, nucleic acids, and some other cell constituents.)
- oxygen (Incorrect. Oxygen is component of many organic compounds and water, but is not the best answer choice.)
- phosphorus (Correct. All organisms require phosphorus to make nucleotides and phospholipids.)
A: phosphorus

Q: ________ is a micronutrient used as an enzyme cofactor by some prokaryotes.
- Iron (Incorrect. Iron is a trace element but is used in electron-transport reactions.)
- Sulfur (Incorrect. Sulfur is actually considered a macronutrient for prokaryotes.)
- Boron (Correct. Boron, chromium, and manganese are all micronutrients used primarily as enzyme cofactors by some prokaryotic organisms.)
A: Boron

Q: Which of the following statements is true about nitrogen?
- It accounts for 50 percent of the composition of a cell. (Incorrect. Nitrogen is not 50 percent of a cell’s composition.)
- It is important for some amino acids and several vitamins and coenzymes. (Incorrect. This does not best describe nitrogen.)
- It presents 12 percent of the dry weight of cells and is a major component of proteins and nucleic acids. (Correct. Nitrogen is present in proteins, nucleic acids, and other cell constituents.)
A: It presents 12 percent of the dry weight of cells and is a major component of proteins and nucleic acids.

Q: Photoautotrophs obtain their energy from ________ and their carbon from ________.
- hydrothermal vents; carbon dioxide (Incorrect. This would be a chemoautotroph; these are found near hydrothermal vents on the deep ocean floor where sunlight does not penetrate.)
- sunlight; carbohydrates (Incorrect. This would be a photoheterotroph. There are a few of these organisms around; they need an organic carbon source to satisfy their carbon requirements because carbon dioxide alone is insufficient.)
- sunlight; carbon dioxide (Correct. The photo indicates sunlight and the auto indicates these organisms can fix inorganic carbon (carbon dioxide) into organic molecules.)
A: sunlight; carbon dioxide

Q: The process of ________ captures inorganic carbon in the form of organic compounds.
- carbon conversion (Incorrect. This is not the term used to describe this process.)
- organic fixation (Incorrect. This is not the term used to describe this process.)
- carbon fixation (Correct. Inorganic carbon from carbon dioxide is “fixed” into organic compounds by autotrophs.)
A: carbon fixation

Q: Which metabolic strategy would be common in extremophiles?
- chemoheterotrophy (Incorrect. Many extreme environments do not support a lot of biological life, so it would be harder to find an organic source of carbon (another organism to eat).)
- photoheterotrophy (Incorrect. Many extreme environments do not support a lot of biological life, so it would be harder to find an organic source of carbon (another organism to eat).)
- chemoautotrophy (Correct. Extremophiles could, and do, survive in extreme environments such as deep sea vents, where alternative energy and carbon sources are present.)
A: chemoautotrophy

Q: The most important biological contribution of carbon dioxide to the atmosphere is through ________.
- respiration from the lungs (Incorrect. This is not the most important biological contributor of atmospheric carbon dioxide.)
- burning organic material (Incorrect. While human energy consumption, including burning organic matter and combustion of fossil fuels, is a significant contributor of excess carbon dioxide to the atmosphere, this is not considered a natural biological contribution.)
- microbial decomposition of dead material (Correct. Prokaryotic organisms break down dead material from organisms that undergo cellular respiration.)
A: microbial decomposition of dead material

Q: In anoxic sediments in aqueous environments, prokaryotes produce ________ as part of a separate carbon cycle that eventually connects with the main, atmospheric-based, carbon cycle.
- carbonate (Incorrect. While carbonate is important in aqueous cycles (it is used to form shells for some organisms, this is not the correct answer.)
- carbon dioxide (Incorrect. While carbon dioxide is present in aqueous environments and does return to the atmosphere, this is not what prokaryotes produce in anoxic environments.)
- methane (Correct. Prokaryotes in anoxic sediments produce methane, which eventually moves through the aqueous environment until it finally converted and returned to the atmosphere in the form of carbon dioxide.)
A: methane

Q: The largest reservoir of available ________ in terrestrial ecosystems is found in land plants.
- oxygen (Incorrect. There is not a specific reservoir of oxygen in terrestrial ecosystems; it is usually taken straight from the atmosphere.)
- nitrogen (Incorrect. Available nitrogen is concentrated in the nodules of legumes.)
- carbon (Correct. In terrestrial systems, the largest amount of available carbon is found in plants.)
A: carbon

Q: Much of the recycling of ________ from organic compounds in carried out by prokaryotes.
- carbon (Incorrect. Carbon is recycled by detritivores.)
- oxygen (Incorrect. Oxygen is readily recycled by everything during cellular respiration and photosynthesis.)
- nitrogen (Correct. Prokaryotes are responsible for most nitrogen recycling in the environment, in particular for fixing gaseous nitrogen into ammonia which can be used for plants.)
A: nitrogen

Q: Ammonification is the process of ________.
- conversion of ammonia to nitrite and nitrate (Incorrect. This is nitrification.)
- reduction of nitrate from soils to gaseous nitrogen compounds (Incorrect. This is denitrification.)
- releasing ammonia during decomposition of nitrogen-containing organic compounds (Correct. This is the release of ammonia during decomposition of organic compounds.)
A: releasing ammonia during decomposition of nitrogen-containing organic compounds

Q: ________ is necessary before plants can assimilate nitrogen compounds via their roots.
- Ammonification (incorrect. This process must occur first to add nitrogen to soils but something else must happen before plants can assimilate the nitrogen.)
- Denitrification (Incorrect. This is the reduction of nitrate from soils to gaseous nitrogen compounds that will enter the atmosphere.)
- Nitrification (Correct. This is the conversion of ammonia to nitrite and nitrate, which is what plants can directly assimilate using their root systems.)
A: Nitrification

Q: The Plague of Athens, which weakened Athens’ dominance and world power, was likely an epidemic of ________.
- bubonic plague (Incorrect. The Plague of Athens was not the bubonic plague.)
- a zoonotic disease (Incorrect. The Plague of Athens is not thought to have been a zoonotic disease.)
- typhoid fever (Correct. Recent studies indicate the Plague of Athens was likely an outbreak of typhoid fever.)
A: typhoid fever

Q: The Black Death was caused by an outbreak of ________.
- a zoonotic disease (Incorrect. This pandemic was not caused by a zoonotic disease though it is transmitted via animals and pests.)
- typhoid fever (Incorrect. This pandemic was not caused by typhoid fever.)
- bubonic plague (Correct. The Black Death was one of the most devastating pandemics caused by the bubonic plague.)
A: bubonic plague

Q: The majority of ________ caused by zoonotic diseases.
- ancient plagues were (Incorrect. Most ancient plagues were not zoonotic diseases.)
- recent epidemics are (Incorrect. There have been few recent epidemics, but so far they were not zoonotic diseases.)
- recently emerging infectious diseases are (Correct. Nearly 75 percent of emerging infectious diseases are zoonotic diseases appearing in humans for the first time.)
A: recently emerging infectious diseases are

Q: Historically, ________ was a common foodborne illness associated with improper sterilization or canning.
- food poisoning (Incorrect. Food poisoning is a generic term for foodborne illnesses.)
- trichinosis (Incorrect. Trichinosis is caused by ingesting roundworms from undercooked meat.)
- botulism (Correct. Botulism is a disease caused by a toxin from the anaerobic bacterium Clostridium botulinum, which proliferated in the low oxygen environment of canned or jarred foods. This also happens to be the source of “Botox.”)
A: botulism

Q: Biofilms are responsible for many foodborne illnesses because ________.
- they are resistant to the heat and pressure used to sterilize food packaging (Incorrect. Biofilms aren’t necessarily resistant to high heat or pressure.)
- they directly infect food items such as spinach leaves (Incorrect. When a biofilm does contaminate an actual food item, that item can be disposed of. This is not why biofilms have such an impact on foodborne illnesses.)
- once they colonize food-processing equipment, they are difficult to eradicate (Correct. As previously discussed, biofilms protect their prokaryotic members from antibiotics and other methods used to control microbial growth. This makes them difficult to remove from food-processing equipment.)
A: once they colonize food-processing equipment, they are difficult to eradicate

Q: Most modern cases of foodborne illnesses are linked to ________.
- undercooked meat (Incorrect. While undercooked meat can cause foodborne illnesses, including trichinosis and cryptosporidiosis, it is not the main source of modern foodborne illnesses.)
- raw dairy (Incorrect. Raw dairy can harbor the causative agents for diseases like listeriosis but this is not the most common cause of modern foodborne illnesses.)
- raw produce (Correct. Most cases of foodborne illness are now linked to contaminated produce, including raw spinach and vegetable sprouts in recent years.)
A: raw produce

Q: Antibiotic resistance appears to be growing in bacteria due to ________.
- antibiotics causing DNA mutations that lead to resistance (Incorrect. Antibiotics do not cause DNA mutations.)
- zoonotic combinations of resistance genes (Incorrect. To date no data indicates bacteria are sharing resistance genes across animal hosts but antibiotics are used heavily in the livestock industry.)
- overuse of antibiotics acting as a selective pressure for resistance adaptations (Correct. Antibiotics kill most of the target bacteria but naturally occurring mutations that make a bacterium resistance will protect it. Once the “weak” are wiped out, the resistant bacteria can proliferate with ample resources.)
A: overuse of antibiotics acting as a selective pressure for resistance adaptations

Q: An increasingly dangerous strain of antibiotic-resistant bacteria is ________.
- E. coli O157:H7 (Incorrect. This is the causative agent in a number of foodborne illness cases but is not antibiotic resistant.)
- H1N1 (Incorrect. H1N1 is actually a strain of the flu, which is a virus. Therefore antibiotics never worked on it.)
- methicillin-resistant Staphylococcus aureus (Correct. MRSA is resistant to a host of antibiotics, not just methicillin, and is becoming prevalent among older and younger populations who live in close quarters.)
A: methicillin-resistant Staphylococcus aureus

Q: Bacteria can exchange genes ________, spreading antibiotic resistance
- with viruses (Incorrect. Bacteria do not exchange genes with viruses.)
- within biofilms (Incorrect. Bacteria cannot exchange genes broadly within biofilms, as there are non-bacterial components to the film.)
- among different species (Correct. Once a single species develops a resistance, that gene may easily spread to other bacterial species, decreasing antibiotic effectiveness globally.)
A: among different species

Q: Biological nitrogen fixation is carried out exclusively by ________.
- fungi (Incorrect. Fungi cannot transform gaseous nitrogen into ammonia.)
- chytrids (Incorrect. Chytrids, a type of fungi, cannot perform nitrogen fixation)
- prokaryotes (Correct. Fixation of nitrogen by biological organisms is only performed by prokaryotes.)
A: prokaryotes

Q: Cyanobacteria are the most important ________ in aquatic systems.
- nitrogenases (Incorrect. Nitrogenases are enzymes.)
- biofertilizers (Incorrect. There are no biofertilizers.)
- nitrogen fixers (Correct. Cyanobacteria are the most important nitrogen fixers in aquatic systems.)
A: nitrogen fixers

Q: In terrestrial systems, most nitrogen fixation involves ________.
- rice (Incorrect. Rice has no role in nitrogen fixation.)
- alfalfa (Incorrect. Alfalfa is the right type of organism but this answer is not broad enough.)
- legumes (Correct. Rhizobia enter the roots of legumes and form nodules; once established, they fix nitrogen from the atmosphere.)
A: legumes

Q: The oldest example of using prokaryotes to make food was likely to make ________.
- bread (Incorrect. While bread has “been around” for many years, it is not the oldest use of prokaryotes for food production.)
- cheese (Incorrect. Cheese likely dates from about 4,000 years ago, which is not the oldest use of prokaryotes for food production.)
- beer (Correct. Evidence exists that the Sumerians made beer about 6,000 years ago, which requires yeast and prokaryotic microbes.)
A: beer

Q: Prokaryotes are used to ________ in the case of processing milk.
- prevent spoilage (Incorrect. While processing milk into cheese will make it last longer, this will not totally prevent spoilage.)
- facilitate product transport (Incorrect. Milk is not processed into other products to make transportation easier.)
- preserve nutrients (Correct. Processing milk into cheese will preserve the nutrients in the milk, though not indefinitely.)
A: preserve nutrients

Q: ________ have/has existed since 4,000 years ago.
- Fermented drinks (Incorrect. It is likely the wine was first invented (or more likely discovered) about 4,500 years ago, while beer production began around 6,000 years ago.)
- Kimchi (Incorrect. Kimchi, or fermented cabbage, has existed since about 1,800 years ago.)
- Cultured milk products (Correct. Cultured milk products such as yogurt were definitely produced 4,000 years ago; cheese may be even older.)
A: Cultured milk products

Q: ________ is the process of utilizing prokaryotes to remove pollutants.
- Microbial vacuuming (Incorrect. This is not the term for using prokaryotes to remove pollutants.)
- Bacterial bioremediation (Incorrect. This term is not inclusive enough for the use of prokaryotes to remove pollutants from the environment.)
- Microbial bioremediation (Correct. Bioremediation can involve a host of prokaryotic organisms, not just bacterial species.)
A: Microbial bioremediation

Q: One of the most successful applications of bioremediation involves cleaning up ________.
- coal runoff (Incorrect. Cleaning up coal runoff is not the most successful use of microbial bioremediation.)
- Superfund sites (Incorrect. Cleaning up Superfund sites is not the most successful use of microbial bioremediation.)
- petroleum (Correct. Prokaryotic organisms have been particularly successful at cleaning up oil spills, degrading up to 80 percent of the nonvolatile compounds within one year of the spill.)
A: petroleum

Q: Bioremediation is not particularly effective at cleaning up ________ from oil spills.
- nonvolatile compounds (Incorrect. Petroleum bioremediation works well for nonvolatile compounds in oil.)
- simple hydrocarbon chains (Incorrect. Several species are able to breakdown simply hydrocarbon chains found in oil.)
- aromatic hydrocarbon chains (Correct. Petroleum bioremediation works well for nonvolatile compounds but not aromatic and highly branched hydrocarbons.)
A: aromatic hydrocarbon chains

Q: It has recently been discovered that microbial species appear to play a particularly strong role in the human ________ system.
- digestive (Incorrect. It has been known for many years that bacteria play a role in our digestive system.)
- integumentary (Incorrect. There are a host of microbes that live on our skin and play a role in pathogen defense, but this has been known for some time.)
- immune (Correct. Growing evidence appears to indicate that disruptions in our normal microbiota may contribute to autoimmune diseases and allergies.)
A: immune

Q: Clinical trials are underway to test the effectiveness of ________ for certain digestive disorders.
- antibiotics (Incorrect. Antibiotics will often disrupt the normal microbiota of the digestive system and actually contribute to disorders.)
- fungal transplants (Incorrect. Fungal organisms are not being tested as a therapeutic for digestive disorders.)
- fecal transplants (Correct. Fecal transplants would return normal, healthy microbiota to digestive systems that are impacted by antibiotic resistant bacteria.)
A: fecal transplants

Q: Some of our microbiota produce ________ for us.
- antigens (Incorrect. Antigens are produced only by our individual immune systems.)
- digestive enzymes (Incorrect. Microbiota in our digestive system may help digest some food, but they actually break down the food.)
- vitamins (Correct. Microbiota in our intestinal tract produce some vitamins such as biotin and folate that humans need and cannot produce on their own.)
A: vitamins