Chapter 22

Compared to free-floating bacteria, bacteria in biofilms often show increased resistance to antibiotics and detergents. Why do you think this might be the case?

Which of the following statements is true? a. Gram-positive bacteria have a single cell wall anchored to the cell membrane by lipoteichoic acid. b. Porins allow entry of substances into both Gram-positive and Gram-negative bacteria. c. The cell wall of Gram-negative bacteria is thick, and the cell wall of Gram-positive bacteria is thin. d. Gram-negative bacteria have a cell wall made of peptidoglycan, whereas Grampositive bacteria have a cell wall made of lipoteichoic acid.

Which of the following statements about the nitrogen cycle is false? a. Nitrogen fixing bacteria exist on the root nodules of legumes and in the soil. b. Denitrifying bacteria convert nitrates (NO3) into nitrogen gas (N2). c. Ammonification is the process by which ammonium ion \(\left(\mathrm{NH}_{4}^{+}\right)\) is released from decomposing organic compounds. d. Nitrification is the process by which nitrites \(\left(\mathrm{NO}_{2}^{-}\right)\) are converted to ammonium ion \(\left(\mathrm{NH}_{4}^{+}\right)\)

The first forms of life on Earth were thought to be _____. a. single-celled plants b. prokaryotes c. insects d. large animals such as dinosaurs

Microbial mats ______. a. are the earliest forms of life on Earth b. obtained their energy and food from hydrothermal vents c. are multi-layered sheets of prokaryotes including mostly bacteria but also archaea d. all of the above

The first organisms that oxygenated the atmosphere were a. cyanobacteria b. phototrophic organisms c. anaerobic organisms d. all of the above

Halophiles are organisms that require ______. a. a salt concentration of at least \(0.2 \mathrm{M}\) b. high sugar concentration c. the addition of halogens d. all of the above

Many of the first prokaryotes to be cultured in a scientific lab were human or animal pathogens. Why would these species be more readily cultured than non- pathogenic prokaryotes? a. Pathogenic prokaryotes are hardier than non-pathogenic prokaryotes. b. Non-pathogenic prokaryotes require more supplements in their growth media. c. Most of the necessary culture conditions could be inferred for pathogenic prokaryotes. d. Pathogenic bacteria can grow as free bacteria, but non-pathogenic bacteria only grow as parts of large colonies.

The presence of a membrane-enclosed nucleus is a characteristic of ________. a. prokaryotic cells b. eukaryotic cells c. all cells d. viruses

Which of the following consist of prokaryotic cells? a. bacteria and fungi b. archaea and fungi c. protists and animals d. bacteria and archaea

The cell wall is ________. a. interior to the cell membrane b. exterior to the cell membrane c. a part of the cell membrane d. interior or exterior, depending on the particular cell

Organisms most likely to be found in extreme environments are _____. a. fungi b. bacteria c. viruses d. archaea

Prokaryotes stain as Gram-positive or Gramnegative because of differences in the cell ______. a. wall b. cytoplasm c. nucleus d. chromosome

Pseudopeptidoglycan is a characteristic of the walls of ______. a. eukaryotic cells b. bacterial prokaryotic cells c. archaean prokaryotic cells d. bacterial and archaean prokaryotic cells

The lipopolysaccharide layer (LPS) is a characteristic of the wall of ______. a. archaean cells b. Gram-negative bacteria c. bacterial prokaryotic cells d. eukaryotic cells

Which of the following elements is not a micronutrient? a. boron b. calcium c. chromium d. manganese

Prokaryotes that obtain their energy from chemical compounds are called ______ a. phototrophs b. auxotrophs c. chemotrophs d. lithotrophs

Ammonification is the process by which ______. a. ammonia is released during the decomposition of nitrogen-containing organic compounds b. ammonium is converted to nitrite and nitrate in soils c. nitrate from soil is transformed to gaseous nitrogen compounds such as \(\mathrm{NO}, \mathrm{N}_{2} \mathrm{O},\) and \(\mathrm{N}_{2}\) d. gaseous nitrogen is fixed to yield ammonia

Plants use carbon dioxide from the air and are therefore called _____. a. consumers b. producers c. decomposer d. carbon fixers

Cyanobacteria harness energy from the sun through photosynthesis, and oxidize water to provide electrons for energy generation. Thus, we classify cyanobacteria as _________. a. photolithotrophs b. photoautotrophs c. chemolithoautotrophs d. chemo-organotrophs

A disease that is constantly present in a population is called _____. a. pandemic b. epidemic c. endemic d. re-emerging

Which of the statements about biofilms is incorrect? a. Biofilms are considered responsible for diseases such as cystic fibrosis. b. Biofilms produce dental plaque, and colonize catheters and prostheses. c. Biofilms colonize open wounds and burned tissue. d. All statements are incorrect.

Which of these statements is true? a. An antibiotic is any substance produced by a organism that is antagonistic to the growth of prokaryotes. b. An antibiotic is any substance produced by a prokaryote that is antagonistic to the growth of other viruses. c. An antibiotic is any substance produced by a prokaryote that is antagonistic to the growth of eukaryotic cells. d. An antibiotic is any substance produced by a prokaryote that prevents growth of the same prokaryote.

A person in England arrives at a medical clinic with a fever and swollen lymph nodes shortly after returning from a visit to New Mexico. For which bacteria should the doctor test the patient? a. Salmonella enterica b. Borrelia burgdorferi c. Clostridium botulinum d. Yersinia pestis

MRSA has emerged as a serious infectious disease, with the first case of methicillin-resistant S. aureus being detected in 1961. Why are medical professionals so concerned when antibiotics exist that can kill MRSA? a. MRSA can transfer methicillin-resistance to other bacteria. b. Patients are not treated with correct antibiotics rapidly enough to prevent serious illness. c. MRSA could acquire additional antibiotic resistance genes from other bacteria to become a “super bug.” d. All of the above.

Which of these occurs through symbiotic nitrogen fixation? a. The plant benefits from using an endless source of nitrogen. b. The soil benefits from being naturally fertilized. c. Bacteria benefit from using photosynthates from the plant. d. All of the above occur.

Synthetic compounds found in an organism but not normally produced or expected to be present in that organism are called _____. a. pesticides b. bioremediators c. recalcitrant compounds d. xenobiotics

Bioremediation includes _____. a. the use of prokaryotes that can fix nitrogen b. the use of prokaryotes to clean up pollutants c. the use of prokaryotes as natural fertilizers d. All of the above

In addition to providing yogurt with its unique flavor and texture, lactic acid-producing bacteria also provide which additional benefit during food production? a. Providing xenobiotics b. Lowering the pH to kill pathogenic bacteria c. Pasteurizing milk products d. Breaking down lactose for lactose-intolerant individuals

Describe briefly how you would detect the presence of a non-culturable prokaryote in an environmental sample.

A new bacterial species is discovered and classified as an endolith, an extremophile that lives inside rock. If the bacteria were discovered in the permafrost of Antarctica, describe two extremophile features the bacteria must possess.

Mention three differences between bacteria and archaea.

Explain the statement that both types, bacteria and archaea, have the same basic structures, but built from different chemical components.

A scientist isolates a new species of prokaryote. He notes that the specimen is a bacillus with a lipid bilayer and cell wall that stains positive for peptidoglycan. Its circular chromosome replicates from a single origin of replication. Is the specimen most likely an Archaea, a Gram-positive bacterium, or a Gram-negative bacterium? How do you know?

Think about the conditions (temperature, light, pressure, and organic and inorganic materials) that you may find in a deep-sea hydrothermal vent. What type of prokaryotes, in terms of their metabolic needs (autotrophs, phototrophs, chemotrophs, etc.), would you expect to find there?

Farmers continually rotate the crops grown in different fields to maintain nutrients in the soil. How would planting soybeans in a field the year after the field was used to grow carrots help maintain nitrogen in the soil?

Imagine a region of soil became contaminated, killing bacteria that decompose dead plants and animals. How would this effect the carbon cycle in the area? Be specific in stating where carbon would accumulate in the cycle.

Explain the reason why the imprudent and excessive use of antibiotics has resulted in a major global problem.

Researchers have discovered that washing spinach with water several times does not prevent foodborne diseases due to E. coli. How can you explain this fact?

Your friend believes that prokaryotes are always detrimental and pathogenic. How would you explain to them that they are wrong?

Many people use antimicrobial soap to kill bacteria on their hands. However, overuse may actually increase the risk of infection. How could this occur?