Q&A Hero

Q: What is the fate of H2 produced within a rumen? A) It is released via eructation (belching). B) It is transformed, along with other ions, into inorganic compounds. C) It is used in acetogenesis. D) It is used in methanogenesis.

Q: What percentage of terrestrial plants are colonized by arbuscular mycorrhizae? A) 10 B) 25 C) 50 D) 85

Q: Two main symbionts of termites are ________ and ________. A) archaea / bacteria B) bacteria / fungi C) bacteria / protists D) fungi / protists

Q: Ruminants digest bacterial cells as a primary source of A) carbohydrates. B) vitamins and proteins. C) proteins. D) vitamins.

Q: How do phototrophic microorganisms benefit when associating with corals? A) Calcium and carbonate ions are released, which help buffer the pH and prevent dramatic pH shifts. B) The coral skeleton is used as a source of bicarbonate for the autotrophic growth of the phototrophs. C) The coral skeleton is an extremely efficient light-gathering structure that greatly enhances light harvesting for photosynthesis. D) The water's temperature in and around the coral skeleton is much warmer.

Q: Which of the following do dinoflagellates most commonly associate with in a mutualistic relationship? A) clams B) corals C) flatworms D) snails

Q: Symbionts such as Aeromonas veronii of leeches and Buchnera symbionts of insects are transmitted ________ to ensure the safe transfer of the symbiont to the next host generation. A) vertically to offspring B) horizontally through infected water C) horizontally through infected secondary hosts D) vertically through the air

Q: Bacterial symbionts of termite hindguts play a critical role in the termite's A) reproduction. B) nitrogen metabolism. C) resistance to fungal infection. D) reproduction and nitrogen metabolism.

Q: Which of the following is a common feature of primary insect symbionts? A) accelerated mutation rates B) extreme genome reduction C) high A+T / low G+C content D) accelerated mutation rates, extreme genome reduction, and high A+T / low G+C content

Q: Horizontal gene transfer between host organisms and their symbionts A) happens frequently because of coevolution. B) causes genome reduction in the symbiont and genome expansion in the host. C) causes genome reduction in both the host and the symbiont. D) has been observed, but is considered a rare event.

Q: In insects, primary symbionts are ________, while secondary symbionts ________. A) heritable / are transmitted horizontally B) able to replicate outside of the host / are obligate symbionts C) required for host reproduction / are not required for host reproduction D) obligate symbionts / have a free-living replicative stage

Q: Which of the following is NOT a major question in the Human Microbiome Project? A) Are differences in the relative abundance of different bacteria important? B) Do differences in the human microbiome correlate with differences in human health? C) Is there a correlation between microbial population structure and host genotype? D) How can we reduce the number of microbes on the human body?

Q: The microbiome contains all A) organisms present on the skin. B) organisms within the digestive system. C) organisms present in and on the body. D) organisms present on the skin and in the digestive system.

Q: Weight gain and obesity may be partly caused by certain gut microbial communities that A) absorb more vitamins and essential amino acids. B) produce more volatile fatty acids by fermentation. C) stimulate the gut endothelium to absorb more sugars. D) produce more hydrogen gas by fermentation.

Q: Which compounds serve as major sources of energy for ruminant animals? A) acetic acid and glucose B) acetic, butyric, and propionic acids C) dimethylsulfoniopropionate, gluconate, and protocatechuate D) glucose and sucrose

Q: The rumen is an ________ habitat that depends on ________ to digest cellulose for ruminant animals. A) aerobic / cellulolytic fungi B) aerobic / cellulolytic and fermentative bacteria C) anaerobic / methanogens D) anaerobic / cellulolytic and fermentative bacteria

Q: How do arbuscular mycorrhizae (AM) help plants obtain more nutrients from the soil? A) Byproducts of AM metabolism serve as primary nutrient sources for the plants. B) The AM increase the total surface area to absorb more nutrients. C) The hyphae develop as specialized nodules that directly produce nutrients for the plant. D) Signaling molecules in the plant are passed to the AM to initiate electron flow, which is in turn used to create ATP.

Q: Where are ectomycorrhizae MOST commonly found? A) boreal and temperate forests B) forests with especially low nutrients C) tropical forests D) boreal and temperate forests, forests with especially low nutrients, and tropical forests

Q: What is the role of the vir genes on a Ti plasmid? A) to cause crow gall disease (virulence) B) to confer resistance to viral infection C) replication of the plasmid D) T-DNA transfer

Q: Which bacterium contains a large Ti plasmid and causes crown gall disease in plants? A) Agrobacterium rhizogenes B) Agrobacterium tumefaciens C) Aliivibrio fischeri D) Butyrivibrio fibrisolvens

Q: The mutualism of Azolla-Anabaena is useful for A) aquaculturalists. B) corn farmers. C) rice farmers. D) tropical forest community succession.

Q: The specificity of certain rhizobia to infect only particular plants is in part due to the A) abundance of nutrients present in the soil. B) nifH genes they possess. C) rhizobial lipids that act as signaling molecules. D) season (time of year).

Q: How is a bacteroid distinguished from a bacterial cell? A) 16S rRNA gene sequencing B) biochemical tests C) cell morphology D) 16S rRNA gene sequencing, biochemical tests, and cell morphology

Q: The function of leghemoglobin in root nodules is to A) bind oxygen. B) chelate iron. C) produce iron. D) produce nitrogen.

Q: Plant root nodules are A) formed from gall-rotting bacteria that decompose plant roots. B) harmful to plants, because the bacteria outcompete the plants for nutrients. C) sites where nitrogen fixation occurs. D) structures created by fungi and are found in all agricultural crops.

Q: Most nitrogen-fixing bacteria symbiotically associated with plants are called A) bacteroids. B) mycorrhizae. C) rhizobia. D) symbiodinia.

Q: The insect symbiont Wolbachia can be used to suppress disease transmission by mosquitoes because A) Wolbachia supplies essential nutrients to the mosquito Culex quinquefasciatus. B) only Wolbachia-infected mosquitoes can transmit viral diseases such as dengue fever. C) Wolbachia infections can spread rapidly through a mosquito population, killing all the mosquitoes. D) Wolbachia-infected male mosquitoes sterilize uninfected female mosquitoes.

Q: Two organisms that both benefit from each other are in a symbiotic relationship called A) ammensalism. B) commensalism. C) mutualism. D) parasitism.

Q: How are symbiotic relationships important in agriculture and food production? Use at least two different examples to support your answer and explain how understanding these symbioses could help produce more food.

Q: The attine ant is entirely dependent on multiple microbial species for its source of food. What microbial species are involved and what is their role in this multi-partner symbiosis?

Q: What is coral bleaching and how might corals be able to adapt to avoid the destruction of coral reefs?

Q: Explain how leeches are used today in medical replants and transplants.

Q: Describe the mutualistic relationship between chemolithotrophic bacteria and tube worms in hydrothermal vents.

Q: How do Hawaiian bobtail squids prevent all bacteria except Allivibrio fischeri from colonizing their light organ?

Q: What is the difference between a primary and secondary insect symbiont? Propose how you might use an insect symbiont to control the spread of an insect-borne disease.

Q: The following quote is taken from a university extension publication for farmers: "Grain poisoning, also known as grain overload or lactic acidosis, is usually the result of stock consuming large quantities of grain or pellets to which they are unaccustomed. Pasture-fed cows or feedlot cattle not yet adapted to grain may become acutely ill or die after eating only moderate amounts of grain, whereas stock accustomed to diets high in grain content may consume large amounts of grain with little or no effect." What is happening in the digestive system of the livestock that causes grain poisoning and why does a gradual shift in diet avoid this problem?

Q: Why was Escherichia coli thought to be a dominant member of the human gut microbial community in the past? What populations ARE important in the human gut and what evidence do we have that the specific bacteria present are important for human health?

Q: Genome sequencing of the bacterial symbionts of animals has allowed us to compare the genomic features of several symbionts. The following data were collected on two insect symbionts: Symbiont A: 0.4 Mb genome, 20% G+C content, missing or incomplete peptidoglycan synthesis and nucleotide synthesis pathways. Symbiont B: 1.8 Mb genome, 40% G+C content, peptidoglycan and most nucleotide synthesis pathways complete. What can you deduce about these two insect symbionts based on their genomes?

Q: Both lichens and corals are symbioses involving phototrophic microorganisms. Compare and contrast lichens and corals, including the types of organisms involved, the role of each partner, the specificity of the interaction, and the method of transmission for each symbiosis.

Q: Coral bleaching is primarily caused by antimicrobials that disrupt the mutualistic relationships formed between corals and their bacterial symbionts.

Q: Molecular evidence suggests that leeches contain two distinct bacterial communities in their bladder.

Q: Biofilms in the human mouth primarily contain pathogens.

Q: Microbial symbionts are horizontally transferred by parental cells directly passing on the symbionts during meiosis.

Q: Due to the close interactions with other organisms, obligate symbionts generally have larger genome sizes compared to other non-symbiotic bacteria.

Q: Gut symbionts are lost after each molting a termite undergoes.

Q: Two-thirds of terrestrial environments support growth of termites.

Q: Obligately symbiotic relationships generally do not foster horizontal gene transfer at a higher rate than non-symbiotic relationships.

Q: Both pathogenic bacteria and primary symbionts have a tendency to lose genes for catabolic pathways.

Q: The reproductive systems of many insects can be manipulated by parasitic symbionts, which are passed down to each generation and can skew the sex ratio of their progeny.

Q: Certain species of Bacteria have been identified to cause obesity.

Q: The gut flora is relatively stable over long time periods in healthy adults, suggesting its highly evolved role in the human body.

Q: The bacterium Escherichia coli comprises a significant fraction of the bacterial population in healthy adult humans, ranging from 10-50%.

Q: Fungi and protists serve an important role in the anaerobic digestion of cellulose in ruminants.

Q: If you were in charge of preserving ancient stone ruins and sculptures in an outdoor environment, what strategies would you use to prevent deterioration of the stone?

Q: What is souring of crude oil and how does the petroleum industry control it?

Q: Which microorganisms commonly thrive in drinking water distribution systems and how might they impact human health?

Q: Trace the flow of raw water through a typical drinking water purification scheme.

Q: Describe floc formation in the activated sludge process.

Q: Compare the operation and function of a trickling filter system and activated sludge.

Q: Describe the general processes that occur in a sludge digester. What is an advantage of sludge digestion over activated sludge?

Q: Natural underground pyritic deposits that are not disturbed by mining activities do not form acidic drainage waters. Why not? Explain the critical steps in the formation of acid mine drainage in your answer.

Q: What microbial processes are involved in the bioremediation of organic pollutants such as hydrocarbons and the bioremediation of inorganic pollutants such as uranium? What are the end products of bioremediation for hydrocarbons and uranium?

Q: Fungi are the main contributor to the biodeterioration of stone building materials and concrete wastewater distribution systems.

Q: Although the sulfate-reducing bacteria are thought to be critical in the corrosion of metal structures, the mechanism of metal corrosion is not well understood.

Q: Chlorinated xenobiotics can ONLY be degraded aerobically, thus making them very recalcitrant if they accumulate in anoxic environments.

Q: Organisms that degrade hydrocarbons in crude oil are ubiquitous in the environment and have evolved special strategies, such as surfactant production, that allow them to readily use hydrocarbons as electron donors and carbon sources.

Q: Bioremediation of uranium depends on metal-reducing bacteria to change the oxidation state of the uranium to form insoluble uranium compounds.

Q: Inorganic pollutants such as metals and radionuclides can be completely destroyed through bioremediation.

Q: Metal-reducing Geobacter and Shewanella species are important in the microbial mining of metals.

Q: Pyrite (FeS2) is common in bituminous coal and metal ores and is a critical component of the microbial leaching of ores and acid mine drainage.

Q: Subway air and water distribution systems harbor dangerous levels of pathogenic microorganisms.

Q: For water to be considered safe to drink, it must be treated with four distinct methods.

Q: Water disinfection agents such as chlorine can easily inactivate viruses.

Q: Chlorine is consumed when it reacts with organic materials.

Q: In water, MOST taste- and odor-producing compounds are inorganic in nature.

Q: Potable water is NOT safe for human consumption.

Q: Secondary treatment may be aerobic or anoxic.

Q: Wastewater plants are usually constructed to handle both domestic and industrial wastes.

Q: MOST wastewater treatment facilities employ methods designed to detect each pathogenic organism that may be present in a given sample.

Q: BOTH physical and chemical methods are used to treat and purify drinking water.