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PROKARYOTES. 1. List unique characteristics that distinguish archaea from bacteria. Archaea  Evolved from the earliest cells  Inhabit only very extreme.

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Presentation on theme: "PROKARYOTES. 1. List unique characteristics that distinguish archaea from bacteria. Archaea  Evolved from the earliest cells  Inhabit only very extreme."— Presentation transcript:


2 1. List unique characteristics that distinguish archaea from bacteria. Archaea  Evolved from the earliest cells  Inhabit only very extreme environments  Only a few hundred species exist Bacteria  The “modern” prokaryotes  Over 10,000 species  Differ structurally, biochemically, and physiologically from Archaea


4 2. Describe the three domain system of classification and explain how it differs from previous systems. 1.Domain Archaea  Archaebacteria 2.Domain Bacteria  Eubacteria 3.Domain Eukarya  all eukaryotes  “domain” is above the Kingdom taxon, and includes all taxa below


6 3. Using a diagram, distinguish among the three most common shapes of prokaryotes. 1.Spheres (cocci) 2.Rods (bacilli) 3.Helices (spirilla & spirochetes)


8 4. Describe the structure and functions of prokaryotic cell walls. 1. Maintain cell shape 2. Protect cell 3. Prevent cell from bursting (hypotonic)  Differ in chemical composition and construction than protists, plants and fungi  Made of peptidoglycan  modified sugar polymers crosslinked by short polypeptides (archaea don’t have it)


10 5. Distinguish between the structure and staining properties of gram-positive and gram-negative bacteria.  Gram stain  a stain used to distinguish two groups of bacteria by virtue of a structural difference in their cell walls  Gram +  simple cell walls with lots of peptidoglycan - these stain blue in color  Gram -  more complex cell walls with less peptidoglycan - Outer lipopolysaccharide-containing membrane that covers the cell wall - these stain pink in color

11 6. Explain why disease-causing gram-negative bacterial species are generally more pathogenic than disease-causing gram-positive bacteria.  The lipopolysaccharides: - these are often toxic and the outer membrane helps protect these bacteria from host defense systems - can impede the entry of drugs into the cells, making gram negative bacteria more resistant to antibiotics

12 7. Describe three mechanisms motile bacteria use to move. 1.Flagella 2.Filaments  characteristic of spirochetes - spiral around cell inside cell wall and rotate like a corkscrew 3.Gliding  glide through a layer of slimy chemicals secreted by the organism - movement may result from flagellar motors that lack the flagellar filaments


14 8. Explain how prokaryotic flagella work and why they are not considered to be homologous to eukaryotic flagella.  Prokaryotic flagella are unique in structure and function  They lack the microtubular structure and rotate rather than whip back and forth  They are not covered by plasma membrane  They are 1/10 the width of eukaryotic flagella


16 9. Explain what is meant by geometric growth.  One cell divides into two, two divide into four, four into eight, etc…  Essentially, growth doubles with each generation

17 10. Distinguish between autotrophs and heterotrophs.  Autotrophs  organisms that synthesize their food from inorganic molecules and compounds - Example: Plants, cyanobacteria  Heterotrophs  organisms that require organic nutrients as their carbon source - Example: Animals, some bacteria

18 11. Describe four modes of bacterial nutrition and give examples of each. 1.Photoautotrophs  use light energy to synthesize organic compounds from CO 2 - examples: plants, cyanobacteria 2.Chemoautotrophs  require CO 2 as a carbon source and obtain energy by oxidizing inorganic compounds like H 2 S, NH 3, Fe 2+ - example: Archaea, Sulfobolus 3.Photoheterotrophs  use light to generate ATP from an organic carbon source (unique to some prokaryotes) 4.Chemoheterotrophs  must obtain organic molecules for energy and as a carbon source - examples: most bacteria and most eukaryotes


20 12. Explain how molecular systematics has been used in developing a classification of prokaryotes.  By comparing energy metabolism  Ribosomal RNA comparisons show prokaryotes diverged into Archaea and Bacteria lineages early – the RNA indicates the presence of “signature sequences” = domain-specific base sequences at comparable locations in ribosomal RNA or other nucleic acids  Bottom line  they found that Archaea have at least as much in common with eukaryotes as they do with bacteria


22 13. List the three main groups of archaea, describe distinguishing features among the groups and give examples of each. 1.Methanogens  named for their unique form of energy metabolism - important decomposers and in digestive system of termites and herbivores 2.Extreme halophiles  like high salinity environments (15 – 20%) - have the pigment bacteriorhodopsin in the plasma membrane - absorb light to pump H + ions out 3.Extreme thermophiles  inhabit HOT environments (60 – 80 degrees Celsius) - one sulfur-metabolizing thermophile lives in 105 ‘C water by underwater hydrothermal vents


24 14. List the major groups of bacteria, describe their mode of nutrition, some characteristic features and representative examples. 1.Spirochetes  helical chemoheterotrophs; flagella; ex: Lyme disease 2.Chlamydias  obligate parasites; gram – cell walls; most common STD – causes blindness 3.Gram positive  some are gram – but grouped here due to molecular systematics; example – Clostridium 4.Cyanobacteria  photoautotrophs; example – Anabaena 5.Proteobacteria  1. Purple bacteria: photoautotrophs; Chromatium 2. Chemoautotrophic: free-living and symbiotic; Rhizobium 3. Chemoheterotrophic: in intestinal tracts; Ecoli, Salmonella

25 15. Explain how the presence of E. coli in public water supplies can be used as an indicator of water quality.  E. coli is found in the intestines and excretion of animals and if found in drinking water or post-plant sewage, the sewage system is bad (leaking, etc)

26 16. Explain why all life on earth depends upon the metabolic diversity of prokaryotes.  Earth’s metabolic diversity is greater among the prokaryotes than all of the eukaryotes  The diversity is a result of adaptive radiation over billions of years  Examples: cyanobacteria – make oxygen saprobes – decompose dead materials

27 17. Describe how humans exploit the metabolic diversity of prokaryotes for scientific and commercial purposes.  The range of purposes has increased through recombinant DNA technology 1.Cultured bacteria to make vitamins and antibiotics 2.Used as simple models of life to learn about metabolism and molecular biology 3.Methanogens digest organic waste at sewage plants 4.Decompose pesticides and other synthetic compounds 5.Make products like acetone and butanol 6.Convert milk into yogurts and cheeses for consumption

28 18. Describe how Streptomyces can be used commercially.  Many of the antibiotics that we now use are produced naturally by members of the genus Streptomyces

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