26. Prokaryotes

Organisms that use light for their energy source and CO₂ for their carbon source are called __________.

In an experiment, a microbiologist put equal numbers of each of the following organisms into a flask of sterile broth, consisting mostly of sugar and a few amino acids. She then placed the flask in the dark. Which of the organisms would be most likely to survive?

The Desulfovibrio bacterium breaks down organic matter (which it must have) and uses sulfate (not oxygen) as an electron acceptor. As a result, it produces hydrogen sulfide (H₂S), accounting for the "rotten egg" smell of swamp muck. Oxygen is a deadly poison to Desulfovibrio. We would call Desulfovibrio a(n) __________.

Choose the list below that contains the substances required by typical nitrogen-fixing cyanobacteria.

What is the role of heterocysts in a cyanobacterial filament?

Biofilms are an example of __________.

Which statement about prokaryotes is true?

Prokaryotes are completely indispensable to which chemical cycle?

A type of ecological relationship called __________ involves one organism living at the expense of another organism.

Which of the following statements about cyanobacteria is/are true?

Ticks that live on deer and field mice are responsible for spreading the bacterium __________, which causes __________.

Which example below is a correct statement about Bacteroides thetaiotaomicron, a bacterium that lives in the human intestines?

Which statement is true regarding cholera?

What do some photosynthetic bacteria use as a source of electrons instead of water? a. oxygen (O2) b. hydrogen sulfide (H2S) c. organic compounds (e.g., CH3COO−) d. nitrate (NO3-)

Photoautotrophs use a. light as an energy source and CO2 as a carbon source. b. light as an energy source and methane as a carbon source. c. N2 as an energy source and CO2 as a carbon source. d. CO2 as both an energy source and a carbon source.

What are organisms called that use inorganic compounds as electron donors in cellular respiration? a. phototrophs b. heterotrophs c. organotrophs d. lithotrophs

What does the chemiosmotic hypothesis claim? a. ATP is generated using phosphates taken from intermediates in the electron transport chain. b. ATP is generated using a phosphate gradient produced by glycolysis and the citric acid cycle. c. ATP is generated using a proton-motive force that is produced by the electron transport chain. d. Water is generated using electrons taken from NADH and FADH2 and transported through the electron transport chain.

Which of the following statements is true? (A)Archaea and bacteria have identical membrane lipids. (B)The cell walls of archaea lack peptidoglycan. (C)Prokaryotes have low levels of genetic diversity. (D)No archaea are capable of using CO2 to oxidize H2, releasing methane.

In terms of nutrition, autotrophs are to heterotrophs as a. kelp are to diatoms. b. archaea are to bacteria. c. slime molds are to algae. d. algae are to slime molds.

Explain how feedback inhibition regulates metabolic pathways.

Which of the following involves metabolic cooperation among prokaryotic cells? a. binary fission b. endospore formation c. biofilms d. photoautotrophy

Which of the following describes a bacterium that lives in the human intestine and causes disease? (A)commensalist (B)decomposer (C)gut mutualist (D)symbiotic pathogen

Bacteria perform the following ecological roles. Which role typically does not involve symbiosis? a. skin commensalist b. decomposer c. gut mutualist d. pathogen

Biologists often use the term 'energy source' as a synonym for 'electron donor.' Why?

Using what you have learned about changes in Gibbs free energy, would you predict the ∆G value of catabolic reactions to be positive or negative? What about anabolic reactions? Justify your answers using the terms 'enthalpy' and 'entropy.'

Explain why prokaryote populations can adapt rapidly to changes in their environment.

Streptococcus mutans obtains energy by oxidizing sucrose. This bacterium is abundant in the mouths of Western European and North American children and is a prominent cause of cavities. The organism is virtually absent in children from East Africa, where tooth decay is rare. Propose a hypothesis to explain this observation. Outline the design of a study that would test your hypothesis.

Streptococcus mutans obtains energy by oxidizing sucrose. This bacterium is abundant in the mouths of Western European and North American children and is a prominent cause of cavities. The organism is virtually absent in children from East Africa, where tooth decay is rare. Propose a hypothesis to explain this observation. Outline the design of a study that would test your hypothesis.

Cyanide (C≡N−) blocks complex IV of the electron transport chain. Suggest a hypothesis for what happens to the ETC when complex IV stops working. Your hypothesis should explain why cyanide poisoning in humans is fatal.

Suppose that you've been hired by a firm interested in using bacteria to clean up organic solvents found in toxic waste dumps. Your new employer is particularly interested in finding cells that are capable of breaking a molecule called benzene into less-toxic compounds. Where would you go to look for bacteria that can metabolize benzene as an energy or carbon source? How would you design an enrichment culture capable of isolating benzene-metabolizing species?

Which of the following experiments could test the hypothesis that bacteria cause ulcers in humans? (Assume each experiment includes a control group.) Explain what evidence would be provided by the results of the experiment. a. Identify the microbes found in the stomachs of ulcer patients. b. Treat a group of ulcer patients with antibiotics. c. Place a group of ulcer patients on a strict low-acid diet. d. Obtain stomach fluid from ulcer patents and feed it to mice.

SCIENTIFIC THINKING Probiotics, foods and supplements that contain living microorganisms, are thought to cure problems of the digestive tract by restoring the natural balance of its microbial community. Sales of these products total billions of dollars a year. Explore the topic of probiotics and evaluate the scientific evidence for their beneficial effects. A good starting point is the website of the U.S. Food and Drug Administration, which regulates advertising claims of health benefits of dietary supplements. U.S. Food and Drug Administration website, www.fda.gov/food/dietary-supplements.

Imagine you are on a team designing a moon base that will be self-contained and self-sustaining. Once supplied with building materials, equipment, and organisms from Earth, the base will be expected to function indefinitely. One of the team members has suggested that everything sent to the base be sterilized so that no bacteria of any kind are present. Do you think this is a good idea? Predict some of the consequences of eliminating all bacteria from an environment.