1. Prokaryotes are ubiquitous and outnumber eukaryotes, inhabiting nearly all environments through symbiotic relationships. They are divided into bacteria and archaea. 2. Prokaryotes differ from eukaryotes in their lack of membrane-bound organelles and smaller genome size. They reproduce through binary fission and genetic variation occurs through transformation, conjugation, and transduction. 3. Prokaryotes play important ecological roles in nutrient cycling as decomposers and through symbiotic relationships, but some are also agents of disease.

1. Chapter 27 Prokaryotes and the Origins of Metabolic

3. I. They’re almost everywhere A. Outnumber all eukaryotic organisms combined 1. Flourish in all habitats 2. Many live in symbiotic relationships

4. B. Bacteria and archaea are the two main branches of prokaryotic evolution Bacteria and archaea used to be grouped as Monerans Now use a two Domain approach (taxonomic group above Kingdom )

5. 3. Molecular studies indicate that Domain Archaea and Domain Bacteria diverged first and that Domain Archaea and Eukarya share a more recent common ancestor

6. Universal common Ancestor Bacteria Archaea Eukarya

7. A Comparison of the Three Domains of Life Present Present Present Nuclear membrane Eukarya Archaea Bacteria

8. Present Absent Absent Membrane-enclosed organelles Eukarya Archaea Bacteria

9. Absent Absent Present Peptidogylcan in cell wall Eukarya Archaea Bacteria

10. Several kinds Several kinds One kind RNA polymerase Eukarya Archaea Bacteria

11. Methionine Methionine Formyl-methionine Initiator amino acid for start of protein synthesis Eukarya Archaea Bacteria

12. Present Present in some genes Absent Introns Eukarya Archaea Bacteria

13. Growth not inhibited Growth not inhibited Growth inhibited Response to antibiotics and streptomycin and chloramphenicol Eukarya Archaea Bacteria

14. 4. Archaea are found in extreme habitats reminiscent of early earth and are referred to as:

15. Thermophiles —thrive in very hot temperatures Halophiles —thrive in highly saline environments like the Dead Sea Methanogens —release methane gas as a by-product of oxidizing hydrogen for energy

18. C. Nearly all prokaryotes have cell walls external to their plasma membranes 1. Cell walls of bacteria contain peptidoglycan , a matrix of polymers of sugars cross-linked by short polypeptides.

19. 2. Gram stain is an important tool for identifying bacteria as “gram positive” (bacteria with walls containing a thick layer of peptidoglycan) or gram negative (bacteria with more complex walls including an outer liposaccharide membrane)

22. 3. Gram negative bacteria are more pathogenic than gram positive because their liposaccharides may be toxic . 4. Outer membrane protects gram negative bacteria from hosts’ defenses and from antibiotics .

23. 5. Many prokaryotes secrete a sticky capsule outside the cell wall that serves as protection and a glue for adhering to a substratum 6. Some may attach by appendages called pili which may be specialized to hold bacteria together during conjugation .

27. D. Most prokaryotes are motile 1. Many have flagella: either several scattered over the cell surface or concentrated at one or both ends 2. These flagella are different from eukaryotic flagella

32. E. The cellular and genomic organization of prokaryotes is fundamentally different from that of eukaryotes 1. No membrane bound organelles 2. DNA is circular , double-stranded and found in region called the nucleoid

34. 3 . Contains one thousandth of the DNA of a eukaryote 4. Smaller rings of DNA called plasmids may carry genes for antibiotic resistance or metabolism of unusual nutrients

35. plasmids reproduce independently may be transferred between bacteria during conjugation

36. F. Populations grow and adapt rapidly 1. Divide asexually by binary fission (much less complicated than mitosis )

37. 2. Methods of genetic recombination transformation --the uptake of genes from the environment conjugation --the direct transfer of genetic material from one bacterium to another transduction --the transfer of genes by a virus

38. 3. Mutations are the major source of genetic variation Generation times may be as short as 20 minutes or as long as 3 hours.

39. 5. Growth stops as a result of exhaustion of nutrients or the toxic accumulation of wastes 6. Some bacteria form endospores , which are tough-walled cells that can resist even boiling water

41. Cell shape Can be spherical (coccus), rods (bacillus), Or helices (spirilla)

43. Cell size 1-5 micrometers in diameter; 1/10 the size of eukaryotic cells

44. Cell surface Cell wall of peptidoglycan which maintains shape, provides physical protection and prevents the cell from bursting in a hypotonic environment

45. Motility Flagella—cause bacteria to spiral and corkscrew

46. Internal Membranes Infoldings of plasma membrane used in respiration; cyanobacteria have thylakoid membranes used in photosynthesis

48. Genome 1 Circular chromosome; may have both “F” and “R” plasmids

49. Reproduction and Growth Binary fission which results in rapid geometric growth Some bacterial genetic recombination is the result of transduction or conjugation in addition to mutation

50. II. Great diversity of Nutritional and metabolic adaptations: all organisms can be classified by how they obtain their energy and organic carbon compounds

51. A. Photoautotrophs— photosynthetic organisms that capture light from the sun but require carbon dioxide to make organic compounds. Cyanobacteria are prokaryotes that are phototrophs.

52. B. Chemoautotrophs—organisms that make organic carbon compounds from carbon dioxide , but get energy by oxidizing inorganic substances such as hydrogen sulfide, ammonia, or ferrous ions.

53. C. Photoheterotrophs—use light for energy but must obtain their carbon in organic form. Some marine prokaryotes use this mode of nutrition.

54. D. Chemoheterotrophs—must consume organic molecules for both energy and carbon . This mode of nutrition is found widely among prokaryotes as well as protists, fungi, and animals .

55. III. Oxygen requirements A. Some prokaryotes cannot grow in the absence of oxygen for cellular respiration and are called obligate aerobes .

56. B. Some prokaryotes are poisoned by oxygen and are called obligate anaerobes . These prokaryotes normally convert energy by fermentation .

57. C. Some prokaryotes are flexible and are called faculative anaerobes and use oxygen if it is present, but can grow by fermentation in an anaerobic environment.

58. IV. Ecological role of Prokaryotes A. Chemical recycling—primary decomposers of dead plant and animal bodies and waste products and thereby recycling matter.

59. B. Involved in symbiotic relationships Mutualism +/+ Commensalism +/neutral Parasitism +/-

61. C. Agents of disease Tuberculosis is caused by Mycobacterium tuberculosis Lyme disease is caused by a spirochette bacterium called Borrelia burgdorferi

63. 2. Usually cause illness by producing poisons called endotoxins

64. Example— Cholera is called by a bacterial exotoxin that causes the human gut to release chloride ions in to the gut and water follows by osmosis