26. Prokaryotes

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) __________.

954

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

557

What is the role of heterocysts in a cyanobacterial filament?

680

Biofilms are an example of __________.

597

Which statement about prokaryotes is true?

952

Prokaryotes are completely indispensable to which chemical cycle?

491

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?

1338

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

470

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

519

Which statement is true regarding cholera?

597

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-)

531

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.

1200

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

622

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.

1060

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.

2210

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.

598

Explain how feedback inhibition regulates metabolic pathways.

596

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

596

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

797

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

898

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

290

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.'

1081

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

465

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.

830

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.

282

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.

1204

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?

247

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.

573

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.

489

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.

585

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

What conclusion can be drawn regarding the relationship between microbiome diversity and mental health in rats?

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

What conclusions can be drawn regarding the impact of FMT from depressed individuals on behaviors associated with depression and anxiety in rats?

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

Probiotics are often marketed as a food or supplement that can help promote a healthy gut. How might a healthy gut microbiome help improve mental health?

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

Why was it important for the rats used in the study to be free of gut microbiota to begin with?

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

Hypothesize how bacteria living in a person’s gut might influence events occurring in the brain.

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

The prefix photo- indicates that an organism will make use of _______ for energy purposes.

33

Biologists can divide living organisms into two groups:autotrophs and heterotrophs, which differ in _________.

33

Organisms that use organic molecules as their source of carbon are called:

45

Organisms that use CO₂ as their source of carbon are called

Chemoheterotrophs:

Cyanobacteria are a group of photosynthetic bacteria. These bacteria use sunlight as their energy source and carbon dioxide as their carbon source. Cyanobacteria are ________________.

Humans are:

Organisms that require oxygen for metabolism are referred to as…

38