Chapter 27 Test and Quiz

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

Borrelia burgdorferi ... Lyme disease. The hallmark of infection is a large rash that appears at the location of the tick bite.

Which statement about prokaryotes is true?

Prokaryotes are widely used for bioremediation. Prokaryotes have been used in sewage treatment for decades, and they are being used to clean up oil spills and radioactive waste.

Why is salt a good preservative to use for foods such as pork and fish?

Prokaryotic cells living in the food will shrink from their cell walls, impacting their ability to reproduce. Along with liquids from the food, the salt forms a hypertonic solution. Water moves from the prokaryotic cells, and the cytoplasm shrinks away from the cell wall.

Which statement is true regarding cholera?

Its symptoms are caused by an exotoxin that stimulates intestinal cells to release chloride ions into the gut. Water follows the chloride ions from the cells through osmosis, leading to diarrhea, extreme dehydration, and electrolyte imbalance.

Which of the following statements is not true?

Not true: Only bacteria have histones associated with DNA. True: Only some archaea use CO2 to oxidize H2, releasing methane. Archaea and bacteria have different membrane lipids. Both archaea and bacteria generally lack membrane-enclosed organelles. The cell walls of archaea lack peptidoglycan.

Which of the following is/are true about R plasmids?

They can be transferred from one bacterium to another via conjugation. They can carry several resistance genes. R plasmids can carry genes that confer resistance to many antibiotics, and they can be transferred via conjugation.

Which of the following involves metabolic cooperation among prokaryotic cells?

biofilms

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

carbon dioxide, nitrogen, water, light, and some minerals. These bacteria are considered some of the most self-sufficient of all organisms.

Scientists hypothesize that the O157:H7 strain of E. coli is so different from the K-12 strain because of __________.

horizontal gene transfer over many years, most likely through the action of bacteriophages. Many of these imported genes are associated with the pathogenic bacterium's invasion of the host.

In the absence of meiosis and sexual reproduction, what general process allows genetic recombination among prokaryotes?

horizontal gene transfer. Horizontal gene transfer by way of transformation, transduction, and conjugation allows bacteria to share genetic material and recombine it.

Prokaryotes are completely indispensable to which chemical cycle?

nitrogen. Nitrogen-fixing bacteria are the only organisms that can fix atmospheric nitrogen into compounds that other organisms can use to build cellular components.

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) __________.

obligate anaerobic chemoheterotroph. Obligate anaerobes are poisoned by oxygen. Chemoheterotrophs must consume organic molecules for both energy and carbon.

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

parasitism. Parasitism is a type of symbiosis that involves one organism living at the expense of another.

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

photoautotrophs. Photoautotrophs are photosynthetic organisms that harness light energy to drive the synthesis of organic compounds from carbon dioxide.

The bacteria that cause tetanus can be killed only by prolonged heating at temperatures considerably above boiling. This suggests that these bacteria __________.

produce endospores. Endospores are extremely heat resistant.

Plasmids __________.

replicate independently of the main chromosome, can be involved in transfer of genetic material between prokaryotic cells, are transferred from one bacterium to another by conjugation, often contain antibiotic resistance genes. Plasmids may also direct the metabolism of rarely encountered nutrients.

What is the role of heterocysts in a cyanobacterial filament?

They carry out only nitrogen fixation. Filaments are colonies of prokaryotic cells. In some cases, photosynthesis and nitrogen fixation cannot occur in a single cell because oxygen inactivates enzymes needed for nitrogen fixation. Heterocysts are specialized cells that carry out only nitrogen fixation.

Which of the following is a difference between bacteria and archaea?

They have different chemicals in their cell membranes and cell walls. Several other structural and metabolic differences also exist between members of the two groups.

How is it possible that as many as 9 million mutations can arise each day in the population of E. coli inhabiting one human?

A large population size and a rapid reproduction rate combine to produce many mutations without a particularly high mutation rate. Simply by rapid multiplication and a very large population with a normal mutation rate, enormous numbers of mutations can arise in a single day.

Which clade of archaea includes most of the extreme thermophiles?

Crenarchaeota The word root cren means "spring," as in "hot spring."

Which of the following statements about transformation is true?

It can be facilitated by cell-surface proteins that recognize compatible DNA. For some bacteria, transformation is a very important source of genetic material, and they have evolved mechanisms to make the process efficient.

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

Some are single cells, whereas others live in filamentous colonies. It can be said that nitrogen-fixing cyanobacteria are the most self-sufficient of all organisms. Some species may carry on nitrogen fixation. They are the only prokaryotes that perform plantlike, oxygenic photosynthesis. Cyanobacteria are photoautotrophs that conduct plantlike photosynthesis, during which they split water, liberating oxygen. Some cyanobacteria are able to use atmospheric nitrogen directly as a source of nitrogen.

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

The bacteria have a mutualistic relationship with the human body. The bacteria obtain food, energy, and shelter in the human intestines. Humans benefit from the many roles these bacteria play, such as involvement in the synthesis of vitamins and the release of antibiotic chemicals that kill other bacteria.

A gram-negative cell wall consists of __________.

a thin layer of peptidoglycan surrounded by an outer membrane containing lipopolysaccharides. Gram-negative bacteria have a thin layer of peptidoglycan and an outer membrane containing lipopolysaccharides.

An F+ bacterial cell __________.

acts as a donor during conjugation. The F+ designation indicates that the bacterial cell has the genes necessary to initiate conjugation and transfer DNA to a receptor cell.

Which subgroup of proteobacteria contains many species that are closely associated with eukaryotic hosts in mutualistic or parasitic relationships?

alpha. Members of this subgroup include Rhizobium, which live in nodules within the roots of legumes and convert atmospheric N2 to compounds that are usable by the plants. This group also gave rise to the mitochondria of eukaryotic cells through endosymbiosis.

Bacteria that __________ tend to have abundant internal membranes.

are photosynthetic. Cyanobacteria have thylakoid membranes, much like those in chloroplasts, that function in photosynthesis.

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?

chemoheterotrophic bacteria. These organisms do not require light and use organic compounds for both energy and carbon.

Which group of bacteria is unusual in that they lack peptidoglycan in their cell walls?

chlamydias. The gram-negative walls of chlamydias are unusual in that they lack peptidoglycan. One species, Chlamydia trachomatis, is the most common cause of blindness in the world.

Plantlike photosynthesis that releases O2 occurs in

cyanobacteria.

Bacteria perform the following ecological roles. Which role typically does not involve symbiosis?

decomposer

Which subgroup of proteobacteria contains many species that are predators of other bacteria?

delta. This group includes species that congregate into relatively large slimy colonies and species that are predators of other bacteria.

Bacterial flagella have a very complex structure composed of 42 distinct proteins. What is the most likely explanation for the evolution of these complex structures?

exaptation. Proteins that were already part of the bacterial body were modified through natural selection to take on new functions as the bacterial flagella.

Prokaryotes found inhabiting the Great Salt Lake would be __________.

extreme halophiles. Extreme halophiles (salt-loving prokaryotes) live in such places as the Great Salt Lake and the Dead Sea.

Portions of the genomes of certain prokaryotic species are very similar to portions of the genomes of distantly related prokaryotes. The process that most likely accounts for this genetic similarity is __________.

horizontal gene transfer. Prokaryotes are adept at obtaining DNA from other sources, including other species of prokaryotes, through the processes of conjugation, transformation, and transduction.

Gram-negative bacteria have __________ peptidoglycan than gram-positive cells, and their cell walls are __________ complex structurally.

less ... more. Gram-negative bacteria do not contain as much peptidoglycan. They have an additional outer membrane with lipopolysaccharides.

Photoautotrophs use

light as an energy source and CO2 as a carbon source.

Genetic variation in bacterial populations cannot result from

meiosis.

Biofilms are an example of __________.

metabolic cooperation among prokaryotic species. Prokaryotes in biofilms send signals to each other, produce structures to channel nutrients in and wastes out, and produce proteins that help the cells adhere to the substrate and to each other.

Which of the following groups of prokaryotes is classified as a member of the domain Archaea?

methanogens. All known methanogens are members of the domain Archaea.