PROKARYOTES

1. PROKARYOTES

2. 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 1. List unique characteristics that distinguish archaea from bacteria.

4. 2. Describe the three domain system of classification and explain how it differs from previous systems. • Domain Archaea Archaebacteria • Domain Bacteria  Eubacteria • 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. • Spheres (cocci) • Rods (bacilli) • 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. • Flagella • Filaments characteristic of spirochetes - spiral around cell inside cell wall and rotate like a corkscrew • 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. 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  10. Distinguish between autotrophs and heterotrophs.

18. 11. Describe four modes of bacterial nutrition and give examples of each. • Photoautotrophs use light energy to synthesize organic compounds from CO2 - examples: plants, cyanobacteria • Chemoautotrophs require CO2 as a carbon source and obtain energy by oxidizing inorganic compounds like H2S, NH3, Fe2+ - example: Archaea, Sulfobolus • Photoheterotrophs use light to generate ATP from an organic carbon source (unique to some prokaryotes) • 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. • Methanogens named for their unique form of energy metabolism - important decomposers and in digestive system of termites and herbivores • Extreme halophiles  like high salinity environments (15 – 20%) - have the pigment bacteriorhodopsin in the plasma membrane - absorb light to pump H+ ions out • 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. • Spirochetes helical chemoheterotrophs; flagella; ex: Lyme disease • Chlamydias  obligate parasites; gram – cell walls; most common STD – causes blindness • Gram positive  some are gram – but grouped here due to molecular systematics; example – Clostridium • Cyanobacteria  photoautotrophs; example – Anabaena • 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 • Cultured bacteria to make vitamins and antibiotics • Used as simple models of life to learn about metabolism and molecular biology • Methanogens digest organic waste at sewage plants • Decompose pesticides and other synthetic compounds • Make products like acetone and butanol • 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