University of Health Sciences Lahore - BIOLOGY 2301

CHAPTER 1: Microbial Life: Origin and Discovery

MULTIPLE CHOICE

1)Viruses are

1. 1. infectious agents that infect exclusively multicellular organisms.
   2. noncellular particles that take over the metabolism of a cell to generate more virus particles.
   3. pathogens that replicate in complex growth media.
   4. cellular particles that belong to the archaea domain.
   5. microbes that consist of lipid membrane–enclosed genomes.

2. Analysis of DNA sequences reveals
   1. the ancient convergence of two cell types (i.e., prokaryotes and eukaryotes).
   2. that prokaryotes and eukaryotes evolved from a common ancestral cell.
   3. that bacteria share a common ancestor with archaea but not with eukarya.
   4. that prokaryotes are cells with a nucleus.
   5. that the genome of Haemophilus influenzae has about 2 billion base pairs.

3. Which of these groups are considered to be microbes but NOT considered to be cells?
   1. viruses                                                     d. protists
   2. bacteria                                                   e.   filamentous fungi
   3. archaea

4. A microbe is commonly defined as a           that requires a microscope to be seen.

5. Which one of the following statements regarding microbial cells is FALSE?
   1. Microbial cells acquire food, gain energy to build themselves, and respond to environmental change.
   2. Most single-celled organisms require a microscope to render them visible, but some

bacterial cells are large enough to be seen with naked eyes.

1. 3. Microbes function as individual entities.
   4. Many microbes form complex multicellular assemblages.
   5. Viruses are not considered microbial cells.

6. Which of the following statements is FALSE?
   1. A genome is the total genetic information contained in an organism’s chromosomal DNA.
   2. If a microbe’s genome includes genes for nitrogenase, that microbe probably can fix nitrogen.
   3. By comparing DNA sequences of different organisms, we can figure out how closely

related they are.

1. 4. Fred Sanger developed the first applicable DNA sequencing method.
   5. Fred Sanger completed the sequences of Haemophilus influenzae.

7. The first cellular genomes to be sequenced were those of
   1. humans.                                                  d. prions.
   2. bacteria.                                                  e.   fungi.
   3. viruses.

8. The environment of early Earth may have contained all of the following EXCEPT
   1. ferrous iron.                                            d. oxygen.
   2. methane.                                                 e.   hydrogen gas.
   3. ammonia.

                                 DIF:     Medium        REF: Special Topic 1.1

9. The development of the theory of the “RNA world” resulted from the discovery of
   1. archaea.                                                  d. ribozymes.
   2. prions.                                                     e.   endosymbionts.
   3. bacteria.

10. What is the evidence that living cells existed on Earth up to 3.8 billion years ago?
    1. microfossils                                             d. Martian folded rock formations
    2. 16S ribosomal RNA                                 e.   diatom shells
    3. Miller and Urey’s experiments

11. What did van Leeuwenhoek discover using microscopic observations before and after drinking hot beverages?

1. 1. Heat did not kill microbes.
   2. Heat killed microbes.
   3. Heat did not kill algae.
   4. Caffeine in coffee killed microbes.
   5. The existence of spiral-shaped microbes.

12. Tyndall’s spontaneous generation experiments occasionally failed due to
    1. nutrient chirality.                                    d. lack of oxygen.
    2. dust.                                                        e.   endospores.
    3. fermentation.

13. The discovery of microbes occurred in the          century?
    1. seventeenth                                            d. twentieth
    2. eighteenth                                               e.   twenty-first
    3. nineteenth

14. Robert Koch won the Nobel Prize for his contribution to medical bacteriology regarding
    1. Escherichia coli.                                      d. rabies.
    2. Bacillus subtilis.                                      e.   smallpox.
    3. Mycobacterium tuberculosis.

15. How did European invaders to North America kill much of the native population?
    1. tuberculosis                                             d. HIV
    2. leprosy                                                    e.   bubonic plague
    3. smallpox

16. Florence Nightingale
    1. is best known as the founder of professional nursing.
    2. was the first to use disinfectant to demonstrate the significance of aseptic technique.
    3. developed the pie chart of mortality data during the Crimean War.
    4. performed the first controlled experiment on the chemical conversion of matter, known today as chemotherapy.
    5. argued that the environment of early Earth contained mainly reduced compounds.

17. Who developed the concept of medical statistics?

18. The first person to visualize individual microbial cells was
    1. Antonie van Leeuwenhoek.                     d.   Lady Montagu.
    2. Robert Hooke.                                         e.   Edward Jenner.
    3. Louis Pasteur.

19. Semmelweis and Lister noted that many of their patients’ deaths were due to
    1. fungi.                                                       d.   pathogen transmission by doctors.
    2. Escherichia coli.                                      e.   Staphylococcus.
    3. chlorine.

20. What is the standard sterilization method for the controlled study of microbes?
    1. boiling                                                     d. autoclaving
    2. pasteurization                                         e.   irradiation
    3. filter sterilization

21. How does the Winogradsky column differ from Koch’s plate media?
    1. Koch’s media creates a gradient from oxygen-rich conditions at the surface to highly reduced conditions below.
    2. The Winogradsky column is used for culturing viruses.
    3. The Winogradsky column is used for growing extremophiles.
    4. The Winogradsky column uses the kinds of nutrients that feed humans.
    5. The bacteria that Winogradsky isolated can grow only on inorganic minerals.

22. Suppose Pasteur’s swan-necked flasks containing boiled broth became cloudy twenty-four hours after boiling. Which choice could best explain the turbidity or cloudiness in the broth without supporting spontaneous generation?
    1. Endospores in the broth survived boiling and grew after the broth cooled.
    2. Contaminating organisms in the broth killed by boiling became alive again after the broth cooled.
    3. Chemicals in the broth came together to form living organisms.
    4. The broth allowed light to pass through it with less interference after boiling.
    5. Solid material in the broth dissolved during boiling.

23. Which of the following is NOT considered to be an extremophilic condition for bacteria?
    1. high alkalinity                                         d. high nutrients
    2. high salinity                                             e.   high temperature
    3. high acidity

24. The use of agar as a more robust gelling agent in solid media was suggested by
    1. Robert Koch.                                           d.   Louis Pasteur.
    2. Ignaz Semmelweis.                                 e.   Richard Petri.
    3. Angelina Hesse.

25. It took the advent of the polymerase chain reaction to detect the presence of the causative agent for which disease?
    1. anthrax                                                    d. rabies
    2. tuberculosis                                             e.   smallpox
    3. AIDS

26. The word “vaccination” is derived from the Latin word vacca, which means
    1. inject.                                                      d. cow.
    2. smallpox.                                                 e.   pustule.
    3. immunize.

27. What was the basis for the original smallpox vaccine?
    1. chickenpox virus                                     d. smallpox virus
    2. cowpox virus                                           e.   anthrax
    3. rabies virus

28. Penicillin was first used to save the lives of many people during which war?
    1. the U.S. Civil War                                    d. World War I
    2. the Korean War                                       e.   World War II
    3. the Vietnam War

29. How do many animal endosymbionts grow?

1. 1. on the surface of the host                       d. on inorganic minerals
   2. on low nutrients                                      e.   in biofilms
   3. by reducing iron oxide

30. All of the following are true about penicillin EXCEPT that it
    1. was discovered by Alexander Fleming.
    2. was an accidental discovery.
    3. is produced by a bacterium.
    4. was the first antibiotic used by humans.
    5. was purified by Florey and Chain.

31. Which of the following statements regarding viruses is FALSE?
    1. Most are too small to be seen by a light microscope.
    2. They are “filterable agents” that can pass through porcelain filters that have a pore size that blocks microbes.
    3. Their genomes could be composed of DNA or RNA.
    4. They are smaller than plasmids and prions.
    5. Viral particles, when pure enough, can be crystallized.

32. You have isolated a bacterium that you believe to be the causative agent of a new disease in frogs. How would you test the third of Koch’s postulates?
    1. Determine the shape of the bacterial cells.
    2. Inject the bacteria into a healthy frog.
    3. Isolate the bacterium from a sick frog.
    4. Show that the bacterium is not present in healthy frogs.
    5. Grow a pure culture of the bacterium outside the frog.

33. How did Sergei Winogradsky grow lithotrophs?
    1. enrichment culture                                 d. endosymbiosis
    2. organic media                                         e.   chain of infection
    3. pure culture

34. Organisms that live symbiotically inside a larger organism are known as
    1. organelles.                                              d. endosymbionts.
    2. cyanobacteria.                                        e.   chloroplasts.
    3. mitochondria.

35. Animal microbiomes are NOT significant in
    1. digesting plant fibers.                             d.   converting ammonia to nitrate.
    2. bioluminescence.                                    e.   providing nutrients to the host.
    3. protection from pathogens.

36. Carl Woese’s discovery replaced the classification scheme of five kingdoms with a scheme of three
    1. phyla.                                                      d.   orders.
    2. domains.                                                 e.   genera.
    3. classes.

37. The gene expression machinery of archaea is MOST similar to
    1. monera.                                                  d. eukaryotes.
    2. prokaryotes.                                            e.   mitochondria.
    3. bacteria.

38. In the three-domain model, the bacterial ancestor of mitochondria derives from ancient
    1. fungi.                                                       d.   archaea.
    2. cyanobacteria.                                        e.   protists.
    3. respiring bacteria.

39. Which of the following organelles are thought to be of prokaryotic origin?
    1. chloroplast                                              d. chloroplast and mitochondria
    2. mitochondria                                          e.   chloroplast and nucleus
    3. nucleus

40. In the three-domain model, the bacterial ancestor of chloroplasts derives from ancient
    1. fungi.                                                       d.   archaea.
    2. cyanobacteria.                                        e.   protists.
    3. proteobacteria.

41. Which commonly used microbial classification advancement led to the tree by Carl Woese in 1977?
    1. comparative genomics                           d. protein sequencing
    2. microscopy                                              e.   16S rRNA sequencing
    3. X-ray diffraction

42. Electron microscopes use what to focus the beam of electrons?

43. Peter Mitchell and Jennifer Moyle discovered the         theory in the 1960s.
    1. germplasm                                              d. DNA synthesis
    2. evolution                                                 e.   polymerase chain reaction
    3. chemiosmotic

44. The X-ray diffraction studies by which of the following scientists concluded that DNA was a double helix?
    1. James Watson                                         d. Maurice Wilkins
    2. Rosalind Franklin                                    e.   Kary Mullis
    3. Francis Crick

45. What feature of bacteria facilitated the DNA revolution in the 1970s?
    1. They are very small.                               d. All of their genes were known.
    2. They readily recombine DNA.                e.   They do not cause disease.
    3. They have very large genomes.

46. This scientist first discovered the process of transformation.
    1. Francis Crick                                           d. Louis Pasteur
    2. Robert Koch                                            e.   Frederick Griffith
    3. Edward Jenner

47. Taq polymerase forms the basis of a technique for
    1. comparative genomics.                          d. DNA amplification.
    2. recombinant DNA.                                  e.   protein synthesis.
    3. X-ray diffraction.

48. In 1975, scientists held a conference at Asilomar to regulate and restrict the field of
    1. recombinant DNA.                                  d. DNA amplification.
    2. comparative genomics.                          e.   forensic microbiology.
    3. DNA sequencing.

49. The study of and cause of disease in humans, animals, and plants is called
    1. microbiology.                                          d. epidemiology.
    2. phylogeny.                                               e.   forensics.
    3. genomics.

50. The ultracentrifuge is a high-speed centrifuge ideally suited for separating individual
    1. cellular proteins and nucleotides.          d. secondary metabolites.
    2. microbial cells.                                       e.   base pairs.
    3. mold spores.

SHORT ANSWER

1. What is the MOST recent evidence suggesting that all life on Earth shares a common ancestry?

2. How are prokaryotes and eukaryotes different?

3. How do microbes help in the extraction of minerals?

4. Antonie van Leeuwenhoek worked as a cloth draper, inspecting the quality of cloth. How did this lead to his interest in microscopy?

5. What was the major complaint about Lazzaro Spallanzani’s experiment to disprove spontaneous generation, and how did Louis Pasteur’s swan-neck flasks overcome this?

6. Describe the discoveries of Louis Pasteur while working with the French beer and wine manufacturers in assessing alcohol versus vinegar production during fermentation.

7. Describe the effects of three microbial diseases that have significantly affected human populations throughout history.

8. Why did it take so long for humans to determine that microbes cause infectious diseases?

9. Robert Koch’s postulates have not been used to prove HIV as the causative agent of AIDS. Why not?

10. Define “attenuation” and describe some mechanisms used to attenuate pathogens.

11. What is the significance of the work of Ignaz Semmelweis and Joseph Lister?

12. How would you use Robert Koch’s postulates to prove that a specific organism causes a new disease in mice?

13. Explain why the organisms that were studied by Sergei Winogradsky could not be grown on Robert Koch’s plate media containing agar or gelatin.

14. Is it true that only culturable bacteria contribute to ecology? Explain your answer.

15. Define the term “endosymbiont” and give an example of an endosymbiotic relationship found in nature.

16. Give two reasons why microbes have been difficult to classify.

17. Briefly explain the endosymbiosis theory and the evidence that supports it.

18. What were Rosalind Franklin’s contributions toward discovering the structure of DNA, and why wasn’t she one of the recipients of the Nobel Prize for this discovery?

19. Briefly describe how the ultracentrifuge is used to determine the sizes of cellular macromolecules.